"Your honor, I could not have possibly shot that person, because yesterday might not have been before today, or at least, there is reasonable doubt that yesterday was before today, according to some physicists on crack. I treat those physicists with high regard personally though, and they have degrees that you don't have, so the court must reasonably conclude their opinions should be entertained."
I guess that's a joke, but it's actually kind of serious that causality, personhood, identity, free will, etc. are all social constructs.
They are useful to us, but every now and then it's helpful and humbling to remember it's a fiction we assign, rather than fundamental.
Criminal justice or the concept of culpability is one of these areas. I know I've seen material by Robert Sapolsky, a neuroscientist who does not believe in free will, talking about how off the mark criminal justice and punishment for crimes can be.
I think it's unclear what kind of determinism you are presuming. Determinism in the universe? Determinism in consciousness? Certainly a deterministic machine can exist in a non-deterministic universe.
However I didn't just assume a lack of free will. I also assumed a lack of identity. Do you realize that who you are is socially defined? When you breathe in, the air in the room around you becomes part of you. When you breathe out, you lose certain gases. When you eat your food, similar story. There's a good case to be made that "you" are in the entire room or the entire food chain. That does make causality and culpability hard to assess objectively. When we do so, we do so subjectively.
Don't be silly. I didn't say anything about shamans. I'm saying human existence is subjective. Culpability, like the courtroom joke above, is subjective. They're useful models for how the world works but it isn't objective reality.
We would do well to remember that every now and then. People who get too into pretending their perspective is objective reality tend to do stupid things.
Isn't identity exactly defined as what one perceives as part of oneself? Food becomes me as soon as I dis-member it to make it to be part of myself. Other food becomes you. This doesn't make food not within my sphere of perception a part of me; before digestion, it stays separate, like a virus doesn't become part of me -- the immune system acts a biological discriminator between what is part of me, and what is not. You are not me, and I am not you; we are physically attached to different matter. I understand people play mind games based on varying definitions of identity, but ultimately you will find that you have control over certain things comprised of physical matter, which then together with your mind makes up "you", and you're not in control of other things, which make them "not you". That's how I would say it is defined, after all. I am not in the entire food chain, because my perception and control simply doesn't reach that far. If I could control objects with my mind, it would be reasonable to say that they are a part of "my body", which makes them a part of me. If you use these language constructs differently, we lose the ability to communicate over them?
Seems like a long-winded way to say you suffer from anxiety.
> like a virus doesn't become part of me -- the immune system acts a biological discriminator between what is part of me, and what is not
But what about symbiotic organisms? What about your microbiome? Or the mitochondria, which began its existence as a separate organism? Or, they say our DNA includes many viruses that our ancestors contracted. A number of these things do stick with us and we sometimes even become totally dependent on them to function.
Exactly? I agree that identity is a fuzzy construct which includes socially constructed elements, and is not a fundamental "thing" that can be observed externally and then named "identity". I disagree that it is therefore "fiction"; as a concept, it is very real? My point was that I don't see how you can claim that identity is nonexistent ("lack of identity"), since the moment I use the term, I "create" and "have" it; it is a flexible enough umbrella to include the distributed system of my body, since I cannot exist separately from it? What "belongs to me" contributes to my identity.
To pick one possible simple and broad definition from WP, "Identity is the set of qualities, beliefs, personality traits, appearance, or expressions that characterize a person or a group." -- you made it sound like that set is empty, which doesn't make sense to me. My identity is part of "I". Every being has an identity; it's not something you can get rid of?
It's been several years and I'm not fresh enough to summarize it, but some time ago I read Carlo Rovelli's "The Order of Time" which is a pop science book on why that isn't true. Ymmv. I'm sure many reading this know more than I do about the topic.
It’s more a philosophical book than a physics book. I’ve only skimmed it, but it presents philosophical views that don’t reflect a scientific consensus.
An interesting corner of philosophy for me is when people worry about perfect clones with all your memories. The only reason it bothers us is because we're not used to our doppelgangers turning up and claiming our sofas and relationships. In a polity where clones are commonplace and provision is made to inform the source and the perfect copy that their material possess will be divided or some stuff will be provided, the shock value would fade away.
Well, it's just a joke. :) It doesn't necessarily have to make a lot of sense.
In any case, I find your comment very interesting. I'm studying quantum computing at the moment, and I've had to read the different interpretations of quantum mechanics, including Everett's many-worlds interpretation. As a non-physicist, I've found the different interpretations fascinating.
The many-worlds one, as far as I understood it, says that all the possible outcomes of a quantum measurement actually "happen" in different worlds. I have the impression that you would be able to give a much better explanation.
In any case, in the joke the gun is shot in the macro world, not in a quantum state. It's possible that it is a quantum gun, but probably not.
The many-worlds theory says that the time-evolution of the (universal) wave function according to the Schrödinger equation is what's real. Different "slices" ("branches") of the wave function correspond to different "worlds". (A "world" is basically defined by what is quantum-entangled together.) The wave function thus decomposes into the different worlds.
Collapse theories, in contrast, state that at specific points in time (the "measurements"), the wave function stops following the Schrödinger equation, and instead collapses to a single slice/branch/world, thus upending the natural proliferation of branches implied by the normal time-evolution of the wave function according to the Schrödinger equation.
Even in many-worlds, however, the wave function doesn't necessarily contain all conceivable worlds. It only contains the worlds, following from some initial quantum state, that follow from the Schrödinger equation. While it's true that all possible outcomes of a quantum measurement become real (because they are all contained in the wave function in superposition), "possible" here means specifically what the equations allow, not any imaginable world.
Eh, the thing about the statement there is you're redefining "universe", which is fine, but restating a definition isn't really saying anything new. The literal meaning of "universe" especially with respect to the Latin origins is... well... everything. It may make sense for physics to separate in to separate sets of everything if there's some reasonable justification.
There's the Universe (everything everywhere everywhen), and then there's the observable universe. Most testable theories will be referring to the observable universe.
As I understand it (I‘m not a cosmologist by any means), saying that the observable universe began at big bang simply means that anything that happened before the big bang has no effect on what happens afterwards.
There may be other universes out there, with their own big bangs, but that has no effect on ours.
Reading this article, I think they are simply disputing the necessity of singularity inside a black hole, and hypothesize a universe which expands from non-singularity black hole, while staying inside its own event-horizon.
That is how I understood it at least, somebody please correct me if I misunderstood it.
Wow, that makes it even dumber. That idea was literally also in Genesis as the original sin of man: "You shall be as Gods."
Edit, for posting too fast: I don't consider the response below to be in good faith, for if there is a God, nothing could be more offensive than to deliberately try to knock him down a few pegs to be "plausible"; while considering the Big Bang to be "plausible" because that doesn't count as "fantasy style magic."
You're being downvoted for a bad read of the material. Any comparisons to God are intentional and deliberate - but mostly serve to knock God down a peg or two by grounding it in something plausible instead of the faith based miracles and straight up fantasy style magic from the Bible.
Futurama has a great episode where Bender meets God (who has merged with a computer) that tackles similar themes.
If you find this to be a harsh reaction, maybe consider how the wording of your initial comment is an effective provocation to anyone who doesn't share your belief system.
Not really. Asimov's story did not represent the process as a mathematically inevitable consequence of physics. It might not even have gone through a second cycle. Cellular life, dollars, and teletypes would all have had to come about again. (-:
There is as yet no proof that there was nothing before the big bang, it's just a supposition. The hot dense universe definitely happened but whether that was the "beginning" is essentially unknown.
We don't. There was never nothing, because there is no "before" the big bang. Time as we know it did not exist until the big bang. It's not there was nothing, it's that there was no there or then.
We don't need it, the same way we don't "need" scientific proof about anything. We could live our whole life pleasing the stakeholders and be happy about it
"beginning" is a misnomer, since time itself started with the Big Bang. There is no such thing as "before" the singularity, as time and space were curved together.
Well, do the calculations of how long it takes for all mass to move around in the initial moments of the big bang. You'll realize that the closer one gets to the singularity, the slower time passes due to time dilation, which means that you'll get the whole eternity to reach the singularity. It only looks like a few seconds from our point of view, looking at the big bang.
Strictly speaking, modern cosmology does not treat the Big Bang as the beginning of all of existence, it's what happens when you take observations about large scale cosmology and run them backwards in time.
Based on the information we have available about our universe, we can't make predictions or formally model anything prior to a certain point in time, consequently it's convenient to treat this moment as the earliest point in time in which physics as we know it makes any sense. So while there may have been some kind of existence prior to the Big Bang, we have no way to make sense of it even at a conceptual level. Given that, we may as well treat this special point in time as the beginning of the universe as we understand it and can explain it using physics, as opposed to some absolute beginning of all of existence.
Only if something exists. But both nothing and something could not exist, and then there is no duality, just nothingness without a something to relate it too.
Isn't time a human invention useful to model the nature? It's literally just a defined interaction as a reference, i.e. the sun rising up and going down which is the rotation of the earth.
So IRL there's no time, there's no need to have a beginning or an end. Whatever happened when all the matter was close together isn't the beginning of anything, just a phase.
We have no idea if there is a meaningful beginning or end, other than heat death. But time is real in the sense that there is an arrow of time, due to entropy.
There's no arrow of entropy, it's an invented useful model to describe something that nature does. Everything is like that, I.e. there's no electric field, it's a useful way to do calculations about particle interactions.
Absolute entropy of a system is calculated either by integrating heat capacity/temp at constant pressure from 0kelvin to the measured temperature, or by calculating via Shannon's method using average amount of information in a discrete random variable.
There is no time factor in any absolute entropy equation.
Empirically, if you measure the entropy of a closed system at a given time, and you measure the entropy of that same closed system at a different time, then calculate the deltas of each, their signs match so long as the time delta is finite and the system isn't empty. So stated plainly, as time increases, so does entropy.
By combining these first principle formulae with the empirical results on entropy, you arrive at the second law of thermodynamics. However, like I said before, we're not really sure why the signs match and it's considered to be an unsolved problem in physics.
There's a perfectly good explanation for why though, in fact the explanation is what motivated the formalism of entropy to begin with. There are significantly more ways that the energy contained within a closed system can spread throughout that system than there are ways for energy contained within a closed system to condense, so that if you observe the state of a system at two different moments in time, you will expect to see it evolve towards the statistically more likely outcome than the statistically less likely outcome.
And from first principles, that's what entropy is, a measure of how energy is dispersed throughout a system. Of course once you have that first principle understanding of entropy then you can come up with more rigorous formalisms to properly quantify what it means for energy to be distributed throughout a system, such as measuring the number of microstates that correspond to a macrostate, and other various formalisms that are more or less equal to each other... but fundamentally they all start from this basic principle.
If time were running against the arrow of entropy, nobody could perceive or measure it, right?
Remembering something is per se an increase in entropy, so the universe could run in negative time direction, but we would simply forget, what had happened.
That said, I personally think such thought experiments are futile and the nature of time has to be understood by its connection to causality and information.
Of course you could perceive it, measure it and record it. The entropy of your body or your brain is not necessarily increasing, nor is the entropy of your computer or other information storage systems.
Entropy only statistically tends towards an increase in closed systems and neither your computer or your brain are closed systems. They are both constantly getting energy from an external source of power and in turn dispersing previously consumed energy out into their environment.
And yet you still manage to perceive things just fine... in fact your perception of the world is unlikely to change whether or not the entropy in your brain increases or decreases by some bounded amount (of course too much of either an increase or decrease will destroy your brain).
Your claim about remembering an event, which likely alludes to Laplace's demon [1], requires an overall increase in entropy in the system as a whole, but does not require an increase in entropy in the specific part of the system that is recording the event.
Every time your computer calls a function like memset(dst, 0), or sorts a list, or arranges data into some kind of structured binary tree, your computer is decreasing its own internal entropy by taking a statistically likely arrangement of bits and transforming it into a very unlikely arrangement of bits. The decrease in the internal entropy of your computer is more than offset by an increase in global entropy but that global entropy is radiating way out into the cosmos and has no impact on your computer's ability to register information.
No, time is what the clock measures. Consciousness does not collapse the wave function meaning clocks exists without humans and time exists without humans.
Exactly, time is whatever the clock measures and the clock does it through some defined physical interaction. Can be a swing of a pendulum, can be vibration of an atom, flow of sand, unwinding of a spring etc.
There are countless versions of this theory out there. Basically, a universe existed, then collapsed down to a single point, and then expanded again (the big bang). Rinse and repeat.
I think it's neat that this summary is written by an author of the scientific manuscript. Oversimplification is a risk, but this approach eliminates the possibility that the writer did not understand the underlying science.
Yea, and it was a great read too. I wish more researchers would publish blog posts alongside their technical whitepapers, although I acknowledge that not everyone involved in science has or wishes to acquire the skills needed to write blog-form content.
(I'd also be worried about a world where researchers are evaluated based on the virality of their blog posts, vs. how impactful their work was.)
I’m not the one you were referring to, but I have similar experiences. I’m living in Germany, and most bigger companies here have such issues. I also worked for companies in Netherlands and Island, so I assume it’s an European, if not global problem.
No one is concerned about keeping people busy. It’s a systemic problem. And there are multiple reasons for it. One reason is that the bigger a company grows, the more hierarchy is necessary. But increasing hierarchy will lead to people doing the work are not the people that are most responsible for it. So we have people that should do the work but they aren’t too motivated because they are not responsible enough - they are too low in hierarchy level. And we have people that are responsible but don’t do the work. They delegate. If something goes wrong or takes too long, they will have enough time and skill to find an excuse.
Another issue is that you need more people to get specific things done. At some point in time these things have been done, and you actually don’t need the amount of people anymore. But you can’t quit them because of worker’s laws. You maybe even don’t want to quit them because you think you still need them. People, of course, tend to find reasons why their own work is important. And they will communicate that. And the chance is good you’ll believe that and don’t question it enough.
There are more reasons for that. But it’s a fact that in many, many companies the economical results of a lot of employees is almost zero. If you don’t believe this, just google the biggest companies in Germany, pick one, apply for an office job and start to work there. It won’t take a month until you’ll find out. Btw. I don’t want to criticize the situation too much. Probably it’s good that people are employed, even if they don’t work efficiently. Otherwise the unemployment rate would be much higher. Then again, Germany‘s economy is flatlining and a crash is not unlikely.
The original claim was "Most jobs are really not important either, they just keep people busy." Causing numbers to change on a balance sheet is not important, unless that corresponds to actual worthwhile work – in which case, the worthwhile work is what matters, and the balance sheet is just an artefact of accounting for it.
The people doing the hiring are typically not the people concerned about profits at medium and large sized companies. Sure someone has to approve the headcount numbers, but realistically this is an extremely flawed process.
Workers generally like jobs where the workload is low. Managers gain status by having bigger teams, whether they need the extra people or not. Even investors often prefer hiring (a sign of growth) to layoffs, and executives are mostly concerned with pleasing investors.
Even well run tech companies with money to burn hired more people than they needed.
An apt analogy. Circling back to scientific research, I'm sure an investigator would be more than happy not to spend the time, effort, and grant money on a project that wasn't going to produce worthwhile results. If only we could know in advance without doing the work.
That does not, of course, mean that "most research being produced isn't really research, just people keeping busy" or whatever other nonsense an uninformed outsider feels like spewing.
Companies can lay off thousands of employees and not have it affect growth, profits or, really, the workload of remaining employees. How could that be possible if everyone's work is so crucial?
Everyone (eh, most) believes their work is crucial.
There are cognitive biases like the self-serving bias, or the IKEA effect, which leads individuals to overvalue their own contributions, as well as subjective importance derived from their immediate impact and daily responsibilities. And of course limited visibility into the broader organizational priorities often obscures how different roles contribute to overall growth and success.
The Bullshit Jobs jobs theory has been widely discredited by researchers, but you probably won't believe them. Consider that most business is B2B so it makes sense that the casual observer would not know what it's for. Additionally, the Bullshit Jobs book relies on a magazine survey, actual studies shows that the percent of people who consider their jobs meaningless is very low and also decreasing over time
I think you're right, but it's not how I remember it for some reason.
I didn't read the book "Bullshit Jobs" [1] as an attempt to quantify how many jobs were bullshit. The author was an anthropologist with no interest in quantifying the economic impact. It's lots of amusing anecdotes from frustrated workers and a nudge for people to question the efficiency of capitalism.
At least that's how I read it. But reading the wikipedia page it sounds like a lot of people fixated on the idea that society could double its efficiency. Hard to know if there's a correct interpretation of the book's claims, and unfortunately we can't ask: the author David Graeber died in 2020.
> while he claims that 50% of jobs are useless, less than 20% of workers feel that way, and those who feel their jobs are useless do not correlate with whether their job is useless. (Garbage collectors, janitors, and other essential workers more often felt like their jobs were useless than people in jobs classified by Graeber as useless.)
Well, again, there is a huge difference between one's own perception of their job being useful or not. I believe garbage collectors, janitors, and nurses, are not examples of useless jobs. Useless jobs are mainly in the office, called "paper pushers". I mean come on, have you not been to any jobs (nor heard of any) where you had to pretend you were busy just to get paid? I saw plenty of cases.
No, but it's a core part of the Bullshit Jobs theory, that the jobs are obviously bullshit to everyone involved. I would suggest that most jobs that aren't particularly valuable are probably not locally recognised as such (i.e. by the person or by their manager).
(In general I think while plenty of people are familiar with varying levels of pointless effort in their jobs, it's rare that a whole job consists of that, at least as far as the person doing it and the person hiring for it are concerned)
>The Bullshit Jobs jobs theory has been widely discredited by researchers, but you probably won't believe them. Consider that most business is B2B so it makes sense that the casual observer would not know what it's for.
I'm not sure how it's possible that anyone over the age of 30 can say something like this with a straight face. Have you ever worked anywhere? I'd love to know how the "researchers" have discredited this. I'd also love to see their other papers (likely, also, bullshit).
There have been countless academics who have discussed this topic, occasionally not behind closed doors. Regardless, it’s certainly my observation as well.
Countless academics have leveled targeted criticisms at various practices and gone on to back those up. They are targeted, actionable objections; not vague blanket dismissals.
Sabine Hossenfelder cast herself out from academia and took a recent turn to monetizing laundering peoples vague understanding string theory is a waste of time (cannot be proven empirically) into academia is doing fake work and if they'd apologize and own up to it, maybe we would trust them again.
Most famously, through a bizarrely written letter from an anonymous whistleblower pleading that she not topple the academy, as it would ruin the lives of thousands of academics making up things to get grant money to survive.
Ran my comment + your reply through AI and asked it to respond to you, as I do want to help. Let me know if there's other instructions I can give it, it may have taken your variable ask too literally? :(
Here's its output:
Sabine Hossenfelder, after distancing herself from academia, has recently pivoted to monetizing a specific narrative:
Let’s define Premise A as “String theory is a waste of time because it cannot be empirically proven.”
She generalizes from Premise A to a broader Claim B: “Academia, more broadly, is producing fake work.”
Her argument seems to imply that:
If academia were to publicly acknowledge this, or apologize for promoting unverifiable theories, then the public might begin to trust it again.
This general thrust reached a kind of crescendo in one of her more notorious moments:
— An oddly written letter, allegedly from a whistleblower within academia, essentially begging her not to “bring down the system.”
The letter’s rationale? That dismantling the status quo would destroy the livelihoods of thousands of academics who, according to the letter, are fabricating just enough plausible-sounding work to secure grants and stay afloat.
Pretty valuable to have people who see A to be true, have presumably seen some of B to be true too (trivial to see with the many replication crises) - and then to do their best to disseminate that to the general public so change can be made. I see no problem there, and I'd hate for the case where people were afraid to make content covering it because they were waiting for years for huge studies (which could also be poorly done) to 'prove' it.
Sabine is an asshole. Doesn't mean she is wrong, and I appreciate when she reads some paper that has made a bunch of headlines to figure out if they're full of crap or not (spoiler alert: the answer is usually yes), but while she can identify the problem she's not part of the solution. Her divorce from academia means she has little power to affect change for the better given how the incentives are currently aligned. She can make a lot of noise, but the people actually pulling the levers have rigged the system in their favor enough to not care.
So she is an arsehole for exposing bullshit? I don't see the problem. I think people take issue with her because of her confrontational persona.
>while she can identify the problem she's not part of the solution
Does she have to be, in principle?
> Her divorce from academia means she has little power to affect change for the better given how the incentives are currently aligned.
Wouldn't be so sure about that. She is getting more public exposure than most academic would in their lifetime. More importantly, exposure to audience _outside_ of academia. Voters. Her effort in creating public awareness has certainly stirred the nest in some academic circles.
This is a good thing. This is where the economy surplus went. Not to 5 days of leisure for everyone. But to jobs that keep us occupied, engaged, and motivated but aren't strictly required. The alternative is just either starving everyone to death, except for a few elite and their slaves, or everyone being bored out of their minds and wondering what the point of life is.
The funding for scientific projects comes from applying for grants from the government. Researchers must write proposals to demonstrate the value of their projects. After the project is completed, they are also required to submit a final report to verify that the project was indeed carried out as approved by the supervising authority.
It's a controversial observation, but it is very true. I work with AI models and have to read recently published research to work with the latest developments in the field.
Do a quick keyword search on papers related to the subject. So much of it is completely useless. It is clearly written to keep people busy, earn credentials, boost credibility. Papers on the most superfluous and tangential subjects just to have a paper to publish.
Very little of it is actually working with the meat of the matter: The core logic and mathematics. It is trend following and busywork. Your sentiment is controversial because people are religiously loyal to the intellectual authorities of these credentialed systems, but a lot of published research does not push any boundaries or discover anything new. This paper seems to be an exception.
I would argue that a lot of the research published in the social sciences also falls under this category. It is there so that someone has a job. I'm not discrediting social sciences in general, am just pointing out that there is a lot of ways to creatively take advantage of academia to secure a paycheck and this is certainly exploited. The kneejerk reaction to reasonable criticism just proves this point even further.
I think the benefits greatly outweigh any dangers. I far prefer to read something like this than something written up by a journalist.
> I acknowledge that not everyone involved in science has or wishes to acquire the skills needed to write blog-form content.
They should. If your research is publicly funded you should make it as available to be public as possible. Academics should be able to communicate, and I very much doubt they are unable to acquire the skills
> I'd also be worried about a world where researchers are evaluated based on the virality of their blog posts, vs. how impactful their work was
Given how bad the measures of impact and the distorted incentives this produces I am not even sure this would even be a bad thing.
If nothing else it improves transparency about what they are doing, again with public money.
>They should. If your research is publicly funded you should make it as available to be public as possible. Academics should be able to communicate, and I very much doubt they are unable to acquire the skills
So in addition to being:
-professional researchers
-professional teachers
-professional project managers
-professional budget specialists
-professional scientific writers
-a failed idea away from losing it all
They should also become:
-professional PR managers
-professional popular writers
While still being paid (poorly) for a single job of all of these.
They should not being doing a lot your first list, and should have specialist help available for some of the rest.
I am not suggesting they become PR managers, and the writing skills I am suggesting they acquire is simply that required to do things like blogging. I am not suggesting they achieve the standards a professional writer would have, just the ability to write clearly and make the effort to do so.
Academics should be highly skilled people.
In fact a lot of the problem is not they cannot do it, but of distribution. A lot of universities to have academic blogs and subsites about departments and individuals research. Its not anything like as visible as the journalists write ups about it
We have similar demands for folks in other professions. I know software engineers who are still coding day to day who also have to manage team budgets and track hours/projects, write patents, write blog posts to make the company look good, mentor juniors, sometimes teach internally or even to external audiences, present at conferences, etc.
Yes, in a perfect world there would be professionals doing this instead of putting it all on the academic.
However, we live in an imperfect world. When people say "should" in these contexts, they're not describing some ideal way the world works. They're prescribing actions that are realistic based on the current system we live in.
The world sucks. It's more useful to work with the small amount of control one has, than to do nothing because the action doesn't solve a wider systemic problem.
> They should. If your research is publicly funded you should make it as available to be public as possible.
The public can access it by becoming subject matter experts. If the government or the public to which it is responsible requires a popsci treatment they can pay other people with this skill set.
I don't doubt having this skill set is useful I merely disclaim any sort of obligation on the part of the scientific staff to possess or exercise such a skill.
Communication skills are often missing in engineering too, but I think I'd argue they should be required - all work is fundamentally collaborative.
Being able to effectively communicate to different people on your team, outside your team, managers, business people, etc is not optional and more than once I've seen things get stalled or turn into a mess because communication didn't happen.
STEM is often a haven for neurodivergence but I think communication skills are something that is largely learned and not something that comes naturally for everyone. People who are good at communicating spend a fair amount of effort rewriting, trying different wordings, different introductions, getting feedback from people, etc.
FWIW I see things like being able to sell a proposal, managing expenses, planning, etc as optional - these are good to have, but someone else can do them if you can communicate well, but in the end the only person who can communicate what you're thinking is you.
"Required" is a bit of a gatekeeper, while I agree good communication skills are valuable.
Blog form content in particular, _requires_ proofing, re-editing, and so on and there's a whole skill set which contributes to makes such content sticky and engaging.
You also seem to be confounding your own point. Indeed all work is collaborative, someone who lacks communication skills, will generally team up with other collaborators who can bring those skills to bear.
A few years ago, at least in my field, there was definitely a trend of people at least doing twitter threads explaining the key findings of their papers. It's obviously less in-depth than a blog post would be, but it was still usually a far more accessible version of the key ideas. Unfortunately, this community has basically dissolved in the last few years due to the changes in twitter and to my knowledge hasn't really converged on a new home.
It's far preferable to having university PR people write some hype piece. Where they'd spend the whole time gushing about it being a world first, paradigm shifting, blah blah blah, the author focuses on things that actually matter. e.g. Is it testable? Yes, here's what to look for.
Yeah, wow. That was great. His solution seems so simple and clears all the previous model's problems. I guess every black hole could contain its own universe.
Too bad the author didn’t explain more the concept of the “parent” universe and how our own (contracting & expanding) universe got created. Nice things to read/consider/ponder late at night :-)
I would be surprised if the size doesn't matter in this case. On the one hand, tiny black holes tend to be rather short-lived. On the other, I suppose some threshold mass/energy is needed to generate a child universe that doesn't collapse immediately.
Ironically that was basically the first thought many had when it was clear we cannot explain what happens in the edge case of a singularity. It was always "perhaps another unsiverse or a way into a parallel one".
It still leaves a lot of questions though, especially if you try to marry quantum mechanics to these makroscopic models. Where did the initial black hole come from and should a corresponsing anti matter black hole exist?
Well that's an indsight bias if I've seen one. This is the first time I ever read that the "bottom" of a black hole could be a entirely new universe. If there ever "always was" a common hypothesis, it was the wormhole.
There wasn't much substance to it back then, but the idea certainly had been circulated in context of singularities where physics break down. So hypothesis is probably an exaggeration.
There used to be a common practice of scientists writing summaries of their research for lay people. I think they viewed it as their civic duty. I had a collection called the World of Physics which included essays written by various scientists. I originally had it in the 90s and found it again after many decades. Would highly recommend.
> The Big Bang is often described as the explosive birth of the universe – a singular moment when space, time and matter sprang into existence.
It is indeed "often described" in the media as such. However, that is _not_ the currently accepted theory. "What if there were no space and time before the Big Bang" is just Stephen Hawking's pet theory.
How so? If you attribute it to an earlier universe, you are just pushing the problem further back. It doesn't seem to be a proof or even a mild indication.
The universe casually didn't follow the laws of physics immediately after the Big Bang, an improbable event directly after an improbable event. No explanation has been found, even according to CERN, why everything that was created was not spontaneously annihilated. Attributing that to a divine intervention is the most probable explanation. CERN attributing this to "Some unknown entity" is humorous.
One theory (which CERN is using) is to argue that almost all matter was destroyed, and that the current observable universe is merely the tiny leftover due to slight differences in behavior, making the Big Bang look more like the Ludicrous Bang. This, of course, just contributes to religious snickering at how all problems are solved by adding another billion years to the timeline, over and over.
Edit to reply: They behave differently; but why there is more of one than the other, remains unexplained; as regardless of how they behave, both should have been initially created in equal numbers. As for Sabine Hossenfelder's quote, that's a religious-faith level cop-out. When science requires faith, should it not be treated as a religion?
> No explanation has been found, even according to CERN
Incorrect.
First, let's be clear, "our understanding of the laws of physics" is not "the actual laws of physics". Every physicist knows this. The universe always follows the real laws, physicists are very excited about the difference because it's a chance to win a Nobel Prize.
For example, the one in 1980 for the discovery (in 1964, they're slow to award the prize) of CP violation in decays of neutral kaons, which is fancy physics language for "matter and antimatter do not behave the same way". This year, the LHCb experiment in CERN also discovered CP violation in baryons.
In fact, this is in your own linked article from CERN: """In the past few decades, particle-physics experiments have shown that the laws of nature do not apply equally to matter and antimatter. Physicists are keen to discover the reasons why."""
That said, personally I like the response from Sabine Hossenfelder: There's nothing to be explained, conservation laws only apply to time-evolution of a system, not to the initial conditions.
We don't look for a reason why the mass-energy was non-zero, why do we even need one for why the baryon number isn't zero?
> Attributing that to a divine intervention is the most probable explanation.
You lost me here. It seems humans have a predisposition to believe in divine beings, so this just sounds like taking human biases as a basis for truth. What's wrong with saying, "I don't know?"
Why not? If you can't observe it, test it, and reproduce it, then it lies outside the realm of science and in the realm of belief. Until someone figures out a way to experimentally verify the big bang hypothesis (or any other explanation for the origin of the universe or what came "before"), it's entirely fair to attribute it to whatever you feel like, be it a god or anything else. There is no law of the universe that guarantees that science is capable of answering all questions.
Well, I think surely the entirely fair thing to do is to just admit we don't know rather than make any attribution or imply any possession of an answer to those questions?
Certainly, that's also perfectly fair. The thing to keep in mind is that some people derive utility from belief in some sort of creator, so ultimately it's an argument of values (specifically, you're looking to argue that people should prefer uncertainty to unprovable (but also undisprovable!) certainty).
Humans have created models for things they don't understand throughout human history. Certainly throughout any recorded history. We don't know, but we have a model that fits pretty well and we can guess at the underlying causes. We'll be wrong more often than right, but over time as we get more data and we can test more things, we get a more accurate model. Not necessarily the right model. We may never get that. But based on those models, "guesses" are far more reliable than "The Sun is a god who circles the world".
While we don't "know" how gravity works we can explain it and model it much more accurately now than when logos was the explanation. Providing those details is far more useful than a simple "we don't know."
If you can't observe it, test it, and reproduce it, then it lies outside of the realm of (natural) science and may lie within the realm of mathematics, philosophy, or (gasp) theology.
> There is no law of the universe that guarantees that science is capable of answering all questions.
There's a name for a more nuanced version of this "law" and there's a good amount of work being done arguing for and against weaker and stronger versions of it: https://plato.stanford.edu/entries/sufficient-reason/
I think it's important to clarify that the question of whether or not everything has a cause is itself outside of science. Science is about determining what a cause is likely to be, using the universe itself as a source of truth, and constrained by fundamental limits on our ability to observe and experiment. Which is to say, even if the philosophers conclude that everything must have a cause, there is still no law that says that we (as scientific agents of a universe that is attempting to understand itself) are capable of determining every possible cause.
Belief in anything is completely trivial unless you act based on those beliefs. No one is going to waste time worshiping, or murder someone over, the "nothing" from before "something".
Anything outside of what we can observe will always be based on faith anyway. We'll probably never understand what's "before" the big bang, wether it make sense to ask that question or why something exists rather than nothing.
On the other hand, there are a lot of stars and different cultures might give them different names and yet there really are many of them.
Furthermore, assume God doesn't exist. Lots of cultures might invent god for various reasons and they'd naturally have different names and attributes for them, which in fact seems to be the current state of affairs.
In fact, if we assume God exists and is actively in communication with humans, its actually a bit weird that different human cultures would have different conceptions and names for that being. Why didn't it just give everyone the same name and information?
Why do you think God will have a name? Name is used by humans to identity a person among a lot of other persons. Why will God have a name if it is the only thing in existence?
To answer the question of why humans give name to God. It's to make god more relatable so that they can workshop it. And use devotion to come closer with it. Look up Bhakti Yoga.
How about just having one God vs many? If there is a single omnipotent being, why do various cultures have multiple gods? And why do different cultures’ gods tell them different things?
Fair question. So my understanding is God is consciousness. It's omnipotent, all knowing and eternal. It's the only thing which is constant in your life and it sees everything you do.
Now, you cannot worship consciousness as humans because it's invisible and you can never imagine it. You need a version of consciousness that you can see as well as you can relate to. So cultures invent localized version of God which people can relate to. And of course it will have attributes similar to that of the culture. But the properties kind of still hold. Like all knowing, powerful etc.
I’m sorry but that’s a lot of words to provide no additional clarity. God is consciousness. So if there are no conscious beings in the universe there is no god? Or is this just renaming something that already has a meaning into god?
This reminds me of what Jordan Peterson does, which is to define "God" as something that we know exists. He defines it as the fundamental value upon which other values are built; you define it as consciousness.
I've always thought arguments like these are unnecessarily applying a term loaded with human conceptions and biases in a way that doesn't shed any further light on the thing it's applied to. Like, what do we gain by defining "God" as consciousness? Why can't we just say "consciousness"? And is it worth the added confusion that when we say "God", we now don't mean what most people think "God" is?
The only reason I can come up with to do this is discomfort at saying, "I don't believe in God."
I didn't say he'd have a name, I said he'd give humans a uniform one since, according to, for instance, the Christian worldview he is purported to be interested in human affairs.
> Various isolated cultures are going to come up with different names for God.
People hate not knowing the answer to the big questions so much that they'll readily accept whatever answers are served up to them.
> This like saying which Sun? Surya, Ra or Helios?
The difference is that the sun is readily observed. A conveniently invisible god isn't.
> All are different names of sun. But there is only one sun.
And there's only one human nature, which is why it's not surprising that common artefacts of human nature (e.g. religion) emerged universally throughout ancient human cultures.
There's quite a big philosophical difference between "there exists a point beyond which it is possible to make observations" and "the universe was created by an omnipotent being"
An illusion is something that disappears when you see behind it, no? How goes it for the illusion of the both of us being connected but separate beings? I think at the very least it would require consent of both parties to merge, so as long as I don’t believe it, you have to live as a being separate from me, and as such it stays „an illusion“ for you that we are one; merely an idea, a potential option maybe, no?
You can declare Life to mean the complex interplay of every living organism, but I don’t see how you can go as far as to claim our physical and mental separateness is not there at all? After all, we need boundaries between „us“ to not be utterly alone. I like to think even of „my“ body more as a federated system, like Life maybe but on a smaller scale. I have some influence on it but not full control. In fact, one could say the polarities in the physical realm are Nature (towards separation, entropy; Kaos) and Life (actively working towards one, requires energy to keep matter ordered; Order).
If we merge, by definition the „I“ and „you“ have to die; both of us stop existing. The merger creates something new, a „we“. A single entity. We can then use the definition of identity to call this new we „I“. Rinse and repeat until back to being alone/all-one?
Do you really want to be all-one? Omnipotent, full of all potentials/possibilities? I don’t know. I am already overwhelmed with my limited human potential/possibilities/options. And I prefer to not be alone. I prefer to stay separate, and keep my identity.
I don't get it. Put all life together and its all pretty obviously NOT omnipotent as far as I can tell. Every living thing on earth could spontaneously have an desire about the state affairs on Pluto and I don't see any reason to believe anything on Pluto would change.
I don't think so - god is substantially less parsimonious. But in the end, I think you're sort of using two different notions of belief as if they were the same.
I believe (lowercase b) in all sorts of stuff, scientific and otherwise, but believing in God typically indicates some kind of act of faith, which is to say, ultimately, to believe in something despite the absence of evidence for it and for some deeper reason than can be furnished by a warrant of some kind. I can believe in the spontaneous generation of the universe in the lowercase b sense of the word without really having anything to do at all with the latter kind of belief, which I think is kind of dumb.
Historically, in the West at least, the ability or inability to reason one's way to the existence of God determined whether you needed to rely on faith or not.
You didn't read closely enough. He is condemning the notion that evolution explains the origin of all things (as ridiculous as that sounds...it was a kind of ontological darwinism; no reasonable person holds this opinion today).
We have no theories working at those conditions. Wiki says
> General relativity also predicts that the initial state of the universe, at the beginning of the Big Bang, was a singularity of infinite density and temperature.[6][obsolete source] However, classical gravitational theories are not expected to be accurate under these conditions, and a quantum description is likely needed[7].
A more accurate summation would be that our theories do not permit us to go back beyond what appears to be the "Big Bang", and indeed, we can't quite get to it either, since the need for Quantum Gravity becomes too great as we get to what seems to be the "zero time". We have no principled, reasonable way to make any claims about what came before the point where our theories break down, and that includes the claim that there was no space or time at all before then.
Thus, anything and everything you've heard about what is there "before the big bang" has always been speculation. I mention this because sometimes people read the science media, which is always reporting on this speculation, and think that the reporting on the speculation constitutes "science" constantly changing its mind, but that's not the case here. Science has consistently not had a justifiable position on this topic, ever. It has always been speculation. It is the press that often fails to make this clear and writes stories in terms of what "science" has "discovered", but any claims of certainty in this area are not the claims of "science".
What people seem to not be able to conceptualize, consciously or not, is that there really is no "before" the Big Bang in the standard model (Lambda-CDM), if time itself exists only after t=0.
The Lambda CDM does not really say that. As other commenters have pointed out, Lambda-CDM is silent on the very earliest few moments of the universe where quantum gravity would be required.
Seems inevitable that we'll discover we aren't the only universe / only cycle.
We went from thinking the Earth was the center of the universe, to the sun being the center of the universe, and the next obvious step is our universe isn't at the center of universes.
Wow, wild this is being taken seriously now perhaps, I first encountered the idea in The Life of The Cosmos ~26 years ago[0] and my impression was the author, Lee Smolin, didn't REALLY beleive it, but he came up with it mostly to have some kind of preferable, falsifiable(er?) alternative to string theory, which he disliked even more, and perhaps more as an idea of the kind of theory we need to explore to start making progress... or that's my memory/impression form 26 years ago, I've been meaning to re-read it for a while since. Anyone read more recently/have other impressions?
(the basic idea was fecund universes/cosmological natural selection[1], such that we should expect to find ourselves, if the theory were true, very near to a local maxima of values such that they approximately maximize the number of black holes produced... but most of the book is really taken up with a fascinating look at the history of physics and ideas...)
I speculate that the big bang is/was fueled by all the black holes that existed and will exist, like a huge cycle where all the energy sucked into black holes converges at the same point in time causing the big bang.
The bounce to me has always seemed more intuitive than the bang, but man, when it comes to the quantum universe I've learned to just check intuition at the door.
> The black hole universe also offers a new perspective on our place in the cosmos. In this framework, our entire observable universe lies inside the interior of a black hole formed in some larger “parent” universe.
Does it also follow that black holes in our universe contain universes internally, beyond their event horizons?! Seems like it should. Mind-blowing.
Not many people these days like to hear this (I myself was one of them), but the answer to this is in Genesis.
There's a reason some of the most famous mathematicians, scientists, engineers, and philosophers of all time believe(d) in God.
The Hebrew name of God, YHWH, literally means "He Who Is." In other words, the Self-Existent One. The father and originator of all things that were, are, and will be, who exists outside of spacetime.
The trouble is we can strive to understand the physical circumstances we find ourselves in. Once we decide that the circumstances simply 'just are' because He Who Is, we no longer have an objective basis for discovering why things are as they are. There's no need, no purpose.
This is not an answer that satisfies just begs more questions.
Who Created God? No one? Why does the universe need a creator if God does not?
Where does free will and evil come from if God is "originator of all things that were, are, and will be". For true free will to exist it must have a source of entropy which denotes something outside of Gods control and design otherwise everything is deterministic as set forth by God.
I understand that many people yearn for a religious explanation to answer the question of what caused the universe to exist. I myself am content with the "it just happened" explanation, as any information prior to the big bang, if it even exists, is unknowable.
There are countless other religions that believe in a deity who created the universe. These deities either created themselves, or had always existed outside of space and time. To that end, any one of those deities would be on equal footing with YHWH. I don't think that it is appropriate to axiomatically claim that a certain deity exists because only that deity could have caused the universe to exist.
I think they mostly "believed" because they would be ostracized and maybe even killed for not believing in God and saying as much. Many who were famous in their lifetimes would have had enemies who would have loved to destroy them via that avenue.
"An equation means nothing to me unless it expresses a thought of God." — Ramanujan
I like to think he was referring to computation. There's a reality to the constant pi, its computation, and ourselves and the representation being part of that same universe.
>There's a reason some of the most famous mathematicians, scientists, engineers, and philosophers of all time believe(d) in God.
That reason being that for much of Western history if you didn't believe in God the Church would burn your research in a big fire and probably you on top of it.
I didn’t understand whether the author is implying that this happens to all black holes or whether the model only applies in some circumstances.
I definitely didn’t understand whether this is suggesting that expanding universes can be contained within black holes that look like fixed-size finite objects from the outside.
And what happens to the inner universe when the parent black hole evaporates through Hawking radiation?
I've often wondered about this. I don't have any direct physics training, but it's something that felt really plausible after I learned that the mass of a black hole is linearly proportional to its swarzschild radius.
As the size of the black hole goes up, its overall density must decrease. Combined with the other observation that our universe has uniform density at large scales, it seemed really obvious to me that there existed some threshold at which the decreasing density of a very large black hole, and the fixed density of our observed universe.. would cross.
I used to muse about this question with some other tech colleagues that liked talking about physics stuff but never really got a clear answer to this.
On a side note - I'm absolutely fascinated by the implications relating to this. I'll post a follow-up thought I'm hoping somebody else has also thought about:
I've seen discussion of dark energy mostly presented as a surrogate for real energy. That there is some underlying energy "accelerating things away from each other".
I always felt uncomfortable with that characterization. It seems more reasonable to me to think of dark energy as _negative energy_ - i.e. a loss of overall energy.
In a classical system, two things moving away from each other stores potential energy that can be recouped at some later time. Dark energy doesn't work this way - things accelerate away from each other the further apart they are. From a global perspective, it's an energy loss.
The energy loss pervades to the quantum world as well - photons that start off high frequency arrive low-frequency.
It somehow feels more appropriate to me to think of dark energy as energy being extracted out of the universe, in some form never to return. Maybe like a black hole evaporating as observed from the inside?
When I asked this of some people in real life, I was pointed to answers that indicated that the "energy" component in dark energy is normalized into the "tension" of space somehow. As I mentioned before I'm not really studied in physics, but that explanation felt unsatisfactory to me.
That is a very interesting idea… the equation and its assumptions doesn’t seem to have any exceptions so it does strongly suggest our universe is a black hole, inside a black hole?
> It somehow feels more appropriate to me to think of dark energy as energy being extracted out of the universe, in some form never to return. Maybe like a black hole evaporating as observed from the inside?
But in this story the black hole increases in size as matter falls into the horizon and shrinks as it evaporates, so cosmic expansion would be associated with more energy falling into the black hole than leaving it.
There was a thread a while ago on here where the hypothesis for why things are moving apart at faster rates is down to time moving at different speeds due to mass.
So time in the void between galaxies is moving quicker than time in the galaxies, but on the grand scale of the universe the differences as up a lot.
I quite liked this theory, think is make sense, at least from my very limited understanding of this stuff.
Yeah, but also that's how time actually works too, time runs slower for us on earth than say GPS satellites so adjustments need calculated to sync the two. Again caveat is I'm more than likely either just wrong or misunderstanding it or massively oversimplifying it.
>follow-up thought I'm hoping somebody else has also thought about [...] dark energy as _negative energy_ [...] Maybe like a black hole evaporating
Another layman's thoughts: Isn't the energy theoretically lost by black holes so faint it's currently undetectable? And isn't the amount of dark energy theorized to be the major component of the observable universe? It seems like the numbers wouldn't add up?
I don't have enough of the background to speculate about the numbers. Dark energy feels "big" if we think of it in terms of the actual energy it would take to accelerate the universe away from itself at the rate that we see.. but the rate that we see is affected by our frame of reference, along with distances and everything else.
I'm gonna pull out my lay understanding again. An evaporating black hole, as it gets smaller, should get more dense and be associated with a higher local spacetime curvature, no? The effect of which would be to slow down apparent time for observers within the system. Maybe that affects observed distance and rates of speed at which things seem to be happening when we look out into the sky?
Sometimes I regret not caring enough about calculus in university.
> Combined with the other observation that our universe has uniform density at large scales
s/has/had at the time of recombination
It is largely an assumption of LCDM that we can treat the universe as practically homogeneous throughout its entire evolution but potentially not a very well-founded at that [0, 1].
> I always felt uncomfortable with that characterization. It seems more reasonable to me to think of dark energy as _negative energy_ - i.e. a loss of overall energy.
Your intuition is correct. If the Lambda term in the Einstein field equations is moved over to the side of the energy momentum tensor, it takes on the role of a negative contribution (provided Lambda > 0, as observations seem to indicate).
> In a classical system, two things moving away from each other stores potential energy that can be recouped at some later time. Dark energy doesn't work this way - things accelerate away from each other the further apart they are. From a global perspective, it's an energy loss.
Note that there is no global energy conservation in General Relativity[2], only at a local scale[3]. Heck, you'll already struggle to define what the energy is of a given piece of spacetime in a meaningful and generic manner[4, 5]. In other words, violations of energy conservation due to spacetime expanding or contracting (a strictly non-local phenomenon), like in the case of the cosmic redshift, are expected and our intuition from classical mechanics only takes you so far.
> It somehow feels more appropriate to me to think of dark energy as energy being extracted out of the universe, in some form never to return.
Dark energy aka the cosmological constant term in the Einstein field equations is a constant term, as the name suggests. Yes, there can be energy loss due to spacetime expanding (see above) but that doesn't change the gravitational constant.
I think a point they are trying to make is that the border of a black hole is only to us outside observers, if you yourself fell into one you wouldn't notice anything specific when you crossed the boundary. The popular example of hawking radiation references a border and pairs of particles, however its actually only to help people understand the idea of what is going on
>> Our universe is expanding. It's density is not fixed.
> None of that precludes uniform density at large scales.
According to observation, the universe is expanding. An argument that it's really static at a large scale would require contradicting observational evidence, but none exists. A theory that requires abandoning observational evidence bears a special burden, which this theory lacks.
The universe's expansion, and a black hole's increase in mass over time, are unrelated phenomena. We could have one without the other. In fact, because of Hawking radiation, in the far future we might see a larger universe accompanied by smaller black holes.
Yeah I was referencing the event horizon as the most meaningful measure of size.
And whether the density is fixed over time or not doesn't affect the question. Let's take the universe at its current average mass/energy density - whatever the "true" measure of that is.
To the best of our understanding, at large scales the density is uniform. So if we consider a suitably large spherical volume of space within our (presumably infinite) universe.. that volume will have an average mass/energy content greater than the threshold amount for a black hole of that apparent volume (again, using the external event horizon frame).
So that suggested to me that either we live in a finite universe, or we must be on the inside of an event horizon. It seems like an unavoidable conclusion.
A black hole is really just a singularity with infinite density by definition, but finite mass.
The size and density of the Schwarzschild volume is determined only by mass (stationary, non-rotating). It's proportional to the inverse square of mass. Density = 3c⁶/32πG³M².
SMBHs have densities ~0.5 kg/m³ between thin air and water.
Stellar BHs are ~1e19 kg/m³ several orders of magnitude more than a neutron star.
I think given time at a blackboard we could walk through Newton's cannon in the context of Poisson gravity, and for extra credit with the cannonball inducing a perturbation of the Poisson vector field. Even without the cannonball's backreaction, the Poisson picture offers a nice image of the gravitational potential energy at the top of the cannonball's inertial (ballistic) curve. We would then consider a cosmology like our own but with a recollapse: at maximum extent there is some (quasi-)Newtonian notion of gravitational potential energy for all the galaxies, since they are at the point where they begin free-falling back into a denser configuration. It's then the usual story of relating kinetic and potential energy, and recognizing that the standard cosmological frame is close to Newtonian by design. (We also have to stop this approach when the galaxies are merging enough that radiation pressure and gas ram pressure become relevant, because the errors become astronomical).
Since we don't have a blackboard in front of us to interact with, I can suggest Alan Guth's lecture notes on Newtonian cosmology. (Guth is credited with discovering cosmic inflation.) https://web.mit.edu/8.286/www/lecn18/ln03-euf18.pdf See around eqn (3.3). You could also borrow a copy of Baumann's textbook <https://www.cambridge.org/highereducation/books/cosmology/53...> which studies the Poisson equation for various spacetimes, however a static spacetime gets most of the focus.
A universe which expands forever, or which expands faster in the later universe, makes a mess of this sort of approach to calculating a gravitational potential energy.
So does any apparent recession velocity that's a large fraction of c (inducing significant redshift, whatever the recession (pseudo-)"force" might be).
However, the general idea is that there is a relationship between the kinetic energy a receding galaxy (in a system of coordinates -- a "frame" -- in which these kinematics appear) and a gravitational potential energy still occurs in a non-recollapsing universe. It's just that the potential energy climbs forever, and you get an equivalent to gravitational time dilation between galaxies at different gravitational potentials (i.e., between early-universe galaxies and higher-potential modern-times galaxies).
Accelerometers in galaxies will not show a cosmic acceleration for any galaxy; they're all really close to freely-falling (local galaxy-galaxy interactions are real -- collisions and mergers and close-calls happen -- but wash out over cosmological distances; look up "peculiar velocity" for details). Therefore we can conclude that there's no real force imposing acceleration on the galaxies. However that's also true of a cannonball in a ballistic trajectory, including one on an escape trajectory or one that enters into a stable orbit. Consequently one can draw some practical comparisons between a ballistic launch from Earth into deep space and galaxies spreading out from an initially denser early part of an expanding cosmos.
> Dark energy as energy being extracted out of the universe
No, it's just a way of thinking about whatever is driving the expansion, and that doesn't dilute away with the expansion as ordinary matter and radiation does. It's not even a "real" energy in the sense that it is only an energy in the cosmological frame, and is a frame-dependent scalar quantity, whereas in the fuller theory it's just a multiplier of the metric tensor. So it's the full relativistic metric doing the work but we absorb some of that into cosmological coordinates in the cosmological fram...
I too read the book and was just searching for anyone mentioning it.
Why can such an idea be called new, when someone else already described it decades ago?
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[ 4.9 ms ] story [ 327 ms ] threadThey are useful to us, but every now and then it's helpful and humbling to remember it's a fiction we assign, rather than fundamental.
Criminal justice or the concept of culpability is one of these areas. I know I've seen material by Robert Sapolsky, a neuroscientist who does not believe in free will, talking about how off the mark criminal justice and punishment for crimes can be.
However I didn't just assume a lack of free will. I also assumed a lack of identity. Do you realize that who you are is socially defined? When you breathe in, the air in the room around you becomes part of you. When you breathe out, you lose certain gases. When you eat your food, similar story. There's a good case to be made that "you" are in the entire room or the entire food chain. That does make causality and culpability hard to assess objectively. When we do so, we do so subjectively.
In that case I dub you a mushroom.
We would do well to remember that every now and then. People who get too into pretending their perspective is objective reality tend to do stupid things.
> like a virus doesn't become part of me -- the immune system acts a biological discriminator between what is part of me, and what is not
But what about symbiotic organisms? What about your microbiome? Or the mitochondria, which began its existence as a separate organism? Or, they say our DNA includes many viruses that our ancestors contracted. A number of these things do stick with us and we sometimes even become totally dependent on them to function.
To pick one possible simple and broad definition from WP, "Identity is the set of qualities, beliefs, personality traits, appearance, or expressions that characterize a person or a group." -- you made it sound like that set is empty, which doesn't make sense to me. My identity is part of "I". Every being has an identity; it's not something you can get rid of?
In any case, I find your comment very interesting. I'm studying quantum computing at the moment, and I've had to read the different interpretations of quantum mechanics, including Everett's many-worlds interpretation. As a non-physicist, I've found the different interpretations fascinating.
The many-worlds one, as far as I understood it, says that all the possible outcomes of a quantum measurement actually "happen" in different worlds. I have the impression that you would be able to give a much better explanation.
In any case, in the joke the gun is shot in the macro world, not in a quantum state. It's possible that it is a quantum gun, but probably not.
Let's say "overruled" then.
Collapse theories, in contrast, state that at specific points in time (the "measurements"), the wave function stops following the Schrödinger equation, and instead collapses to a single slice/branch/world, thus upending the natural proliferation of branches implied by the normal time-evolution of the wave function according to the Schrödinger equation.
Even in many-worlds, however, the wave function doesn't necessarily contain all conceivable worlds. It only contains the worlds, following from some initial quantum state, that follow from the Schrödinger equation. While it's true that all possible outcomes of a quantum measurement become real (because they are all contained in the wave function in superposition), "possible" here means specifically what the equations allow, not any imaginable world.
There may be other universes out there, with their own big bangs, but that has no effect on ours.
Reading this article, I think they are simply disputing the necessity of singularity inside a black hole, and hypothesize a universe which expands from non-singularity black hole, while staying inside its own event-horizon.
That is how I understood it at least, somebody please correct me if I misunderstood it.
Edit, for posting too fast: I don't consider the response below to be in good faith, for if there is a God, nothing could be more offensive than to deliberately try to knock him down a few pegs to be "plausible"; while considering the Big Bang to be "plausible" because that doesn't count as "fantasy style magic."
Futurama has a great episode where Bender meets God (who has merged with a computer) that tackles similar themes.
If you find this to be a harsh reaction, maybe consider how the wording of your initial comment is an effective provocation to anyone who doesn't share your belief system.
But a cycling of a previous universe.
I was a little unclear on the ending, where he says this theory would place our entire universe "inside" a black hole of a parent universe.
All in all, it does seem to tie up some loose ends, and suggest some order to what previously required speculation.
Based on the information we have available about our universe, we can't make predictions or formally model anything prior to a certain point in time, consequently it's convenient to treat this moment as the earliest point in time in which physics as we know it makes any sense. So while there may have been some kind of existence prior to the Big Bang, we have no way to make sense of it even at a conceptual level. Given that, we may as well treat this special point in time as the beginning of the universe as we understand it and can explain it using physics, as opposed to some absolute beginning of all of existence.
So IRL there's no time, there's no need to have a beginning or an end. Whatever happened when all the matter was close together isn't the beginning of anything, just a phase.
There is no time factor in any absolute entropy equation.
Empirically, if you measure the entropy of a closed system at a given time, and you measure the entropy of that same closed system at a different time, then calculate the deltas of each, their signs match so long as the time delta is finite and the system isn't empty. So stated plainly, as time increases, so does entropy.
By combining these first principle formulae with the empirical results on entropy, you arrive at the second law of thermodynamics. However, like I said before, we're not really sure why the signs match and it's considered to be an unsolved problem in physics.
https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_p...
And from first principles, that's what entropy is, a measure of how energy is dispersed throughout a system. Of course once you have that first principle understanding of entropy then you can come up with more rigorous formalisms to properly quantify what it means for energy to be distributed throughout a system, such as measuring the number of microstates that correspond to a macrostate, and other various formalisms that are more or less equal to each other... but fundamentally they all start from this basic principle.
That said, I personally think such thought experiments are futile and the nature of time has to be understood by its connection to causality and information.
Entropy only statistically tends towards an increase in closed systems and neither your computer or your brain are closed systems. They are both constantly getting energy from an external source of power and in turn dispersing previously consumed energy out into their environment.
And yet you still manage to perceive things just fine... in fact your perception of the world is unlikely to change whether or not the entropy in your brain increases or decreases by some bounded amount (of course too much of either an increase or decrease will destroy your brain).
Your claim about remembering an event, which likely alludes to Laplace's demon [1], requires an overall increase in entropy in the system as a whole, but does not require an increase in entropy in the specific part of the system that is recording the event.
Every time your computer calls a function like memset(dst, 0), or sorts a list, or arranges data into some kind of structured binary tree, your computer is decreasing its own internal entropy by taking a statistically likely arrangement of bits and transforming it into a very unlikely arrangement of bits. The decrease in the internal entropy of your computer is more than offset by an increase in global entropy but that global entropy is radiating way out into the cosmos and has no impact on your computer's ability to register information.
[1] https://en.wikipedia.org/wiki/Laplace%27s_demon
It's useful because its quantifiable.
https://news.ycombinator.com/item?id=39271752
Is it the same universal every time? If so, see you later alligator.
(I'd also be worried about a world where researchers are evaluated based on the virality of their blog posts, vs. how impactful their work was.)
This is generally not a problem in the US.
Workers generally like jobs where the workload is low. Managers gain status by having bigger teams, whether they need the extra people or not. Even investors often prefer hiring (a sign of growth) to layoffs, and executives are mostly concerned with pleasing investors.
Even well run tech companies with money to burn hired more people than they needed.
I still remember the joke from my first job:
Q: How many people work at this office?
A: About half.
That does not, of course, mean that "most research being produced isn't really research, just people keeping busy" or whatever other nonsense an uninformed outsider feels like spewing.
There are cognitive biases like the self-serving bias, or the IKEA effect, which leads individuals to overvalue their own contributions, as well as subjective importance derived from their immediate impact and daily responsibilities. And of course limited visibility into the broader organizational priorities often obscures how different roles contribute to overall growth and success.
I didn't read the book "Bullshit Jobs" [1] as an attempt to quantify how many jobs were bullshit. The author was an anthropologist with no interest in quantifying the economic impact. It's lots of amusing anecdotes from frustrated workers and a nudge for people to question the efficiency of capitalism.
At least that's how I read it. But reading the wikipedia page it sounds like a lot of people fixated on the idea that society could double its efficiency. Hard to know if there's a correct interpretation of the book's claims, and unfortunately we can't ask: the author David Graeber died in 2020.
[1]: https://en.wikipedia.org/wiki/Bullshit_Jobs
Well, again, there is a huge difference between one's own perception of their job being useful or not. I believe garbage collectors, janitors, and nurses, are not examples of useless jobs. Useless jobs are mainly in the office, called "paper pushers". I mean come on, have you not been to any jobs (nor heard of any) where you had to pretend you were busy just to get paid? I saw plenty of cases.
Worth to point out that there is a huge difference between people considering their jobs meaningless AND their job being meaningless, though.
(In general I think while plenty of people are familiar with varying levels of pointless effort in their jobs, it's rare that a whole job consists of that, at least as far as the person doing it and the person hiring for it are concerned)
I'm not sure how it's possible that anyone over the age of 30 can say something like this with a straight face. Have you ever worked anywhere? I'd love to know how the "researchers" have discredited this. I'd also love to see their other papers (likely, also, bullshit).
Most famously, through a bizarrely written letter from an anonymous whistleblower pleading that she not topple the academy, as it would ruin the lives of thousands of academics making up things to get grant money to survive.
Ran my comment + your reply through AI and asked it to respond to you, as I do want to help. Let me know if there's other instructions I can give it, it may have taken your variable ask too literally? :(
Here's its output:
Sabine Hossenfelder, after distancing herself from academia, has recently pivoted to monetizing a specific narrative: Let’s define Premise A as “String theory is a waste of time because it cannot be empirically proven.”
She generalizes from Premise A to a broader Claim B: “Academia, more broadly, is producing fake work.”
Her argument seems to imply that:
If academia were to publicly acknowledge this, or apologize for promoting unverifiable theories, then the public might begin to trust it again.
This general thrust reached a kind of crescendo in one of her more notorious moments: — An oddly written letter, allegedly from a whistleblower within academia, essentially begging her not to “bring down the system.” The letter’s rationale? That dismantling the status quo would destroy the livelihoods of thousands of academics who, according to the letter, are fabricating just enough plausible-sounding work to secure grants and stay afloat.
>while she can identify the problem she's not part of the solution
Does she have to be, in principle?
> Her divorce from academia means she has little power to affect change for the better given how the incentives are currently aligned.
Wouldn't be so sure about that. She is getting more public exposure than most academic would in their lifetime. More importantly, exposure to audience _outside_ of academia. Voters. Her effort in creating public awareness has certainly stirred the nest in some academic circles.
Do a quick keyword search on papers related to the subject. So much of it is completely useless. It is clearly written to keep people busy, earn credentials, boost credibility. Papers on the most superfluous and tangential subjects just to have a paper to publish.
Very little of it is actually working with the meat of the matter: The core logic and mathematics. It is trend following and busywork. Your sentiment is controversial because people are religiously loyal to the intellectual authorities of these credentialed systems, but a lot of published research does not push any boundaries or discover anything new. This paper seems to be an exception.
I would argue that a lot of the research published in the social sciences also falls under this category. It is there so that someone has a job. I'm not discrediting social sciences in general, am just pointing out that there is a lot of ways to creatively take advantage of academia to secure a paycheck and this is certainly exploited. The kneejerk reaction to reasonable criticism just proves this point even further.
> I acknowledge that not everyone involved in science has or wishes to acquire the skills needed to write blog-form content.
They should. If your research is publicly funded you should make it as available to be public as possible. Academics should be able to communicate, and I very much doubt they are unable to acquire the skills
> I'd also be worried about a world where researchers are evaluated based on the virality of their blog posts, vs. how impactful their work was
Given how bad the measures of impact and the distorted incentives this produces I am not even sure this would even be a bad thing.
If nothing else it improves transparency about what they are doing, again with public money.
So in addition to being:
-professional researchers
-professional teachers
-professional project managers
-professional budget specialists
-professional scientific writers
-a failed idea away from losing it all
They should also become:
-professional PR managers
-professional popular writers
While still being paid (poorly) for a single job of all of these.
I am not suggesting they become PR managers, and the writing skills I am suggesting they acquire is simply that required to do things like blogging. I am not suggesting they achieve the standards a professional writer would have, just the ability to write clearly and make the effort to do so.
Academics should be highly skilled people.
In fact a lot of the problem is not they cannot do it, but of distribution. A lot of universities to have academic blogs and subsites about departments and individuals research. Its not anything like as visible as the journalists write ups about it
However, we live in an imperfect world. When people say "should" in these contexts, they're not describing some ideal way the world works. They're prescribing actions that are realistic based on the current system we live in.
The world sucks. It's more useful to work with the small amount of control one has, than to do nothing because the action doesn't solve a wider systemic problem.
The public can access it by becoming subject matter experts. If the government or the public to which it is responsible requires a popsci treatment they can pay other people with this skill set.
I don't doubt having this skill set is useful I merely disclaim any sort of obligation on the part of the scientific staff to possess or exercise such a skill.
Being able to effectively communicate to different people on your team, outside your team, managers, business people, etc is not optional and more than once I've seen things get stalled or turn into a mess because communication didn't happen.
STEM is often a haven for neurodivergence but I think communication skills are something that is largely learned and not something that comes naturally for everyone. People who are good at communicating spend a fair amount of effort rewriting, trying different wordings, different introductions, getting feedback from people, etc.
FWIW I see things like being able to sell a proposal, managing expenses, planning, etc as optional - these are good to have, but someone else can do them if you can communicate well, but in the end the only person who can communicate what you're thinking is you.
Blog form content in particular, _requires_ proofing, re-editing, and so on and there's a whole skill set which contributes to makes such content sticky and engaging.
You also seem to be confounding your own point. Indeed all work is collaborative, someone who lacks communication skills, will generally team up with other collaborators who can bring those skills to bear.
It still leaves a lot of questions though, especially if you try to marry quantum mechanics to these makroscopic models. Where did the initial black hole come from and should a corresponsing anti matter black hole exist?
https://www.amazon.com/World-Physics-Library-Literature-Anti...
It is indeed "often described" in the media as such. However, that is _not_ the currently accepted theory. "What if there were no space and time before the Big Bang" is just Stephen Hawking's pet theory.
One theory (which CERN is using) is to argue that almost all matter was destroyed, and that the current observable universe is merely the tiny leftover due to slight differences in behavior, making the Big Bang look more like the Ludicrous Bang. This, of course, just contributes to religious snickering at how all problems are solved by adding another billion years to the timeline, over and over.
https://home.cern/science/physics/matter-antimatter-asymmetr...
Edit to reply: They behave differently; but why there is more of one than the other, remains unexplained; as regardless of how they behave, both should have been initially created in equal numbers. As for Sabine Hossenfelder's quote, that's a religious-faith level cop-out. When science requires faith, should it not be treated as a religion?
Incorrect.
First, let's be clear, "our understanding of the laws of physics" is not "the actual laws of physics". Every physicist knows this. The universe always follows the real laws, physicists are very excited about the difference because it's a chance to win a Nobel Prize.
For example, the one in 1980 for the discovery (in 1964, they're slow to award the prize) of CP violation in decays of neutral kaons, which is fancy physics language for "matter and antimatter do not behave the same way". This year, the LHCb experiment in CERN also discovered CP violation in baryons.
In fact, this is in your own linked article from CERN: """In the past few decades, particle-physics experiments have shown that the laws of nature do not apply equally to matter and antimatter. Physicists are keen to discover the reasons why."""
That said, personally I like the response from Sabine Hossenfelder: There's nothing to be explained, conservation laws only apply to time-evolution of a system, not to the initial conditions.
We don't look for a reason why the mass-energy was non-zero, why do we even need one for why the baryon number isn't zero?
You lost me here. It seems humans have a predisposition to believe in divine beings, so this just sounds like taking human biases as a basis for truth. What's wrong with saying, "I don't know?"
While we don't "know" how gravity works we can explain it and model it much more accurately now than when logos was the explanation. Providing those details is far more useful than a simple "we don't know."
> There is no law of the universe that guarantees that science is capable of answering all questions.
There's a name for a more nuanced version of this "law" and there's a good amount of work being done arguing for and against weaker and stronger versions of it: https://plato.stanford.edu/entries/sufficient-reason/
Various isolated cultures are going to come up with different names for God.
This like saying which Sun? Surya, Ra or Helios?
All are different names of sun. But there is only one sun.
Furthermore, assume God doesn't exist. Lots of cultures might invent god for various reasons and they'd naturally have different names and attributes for them, which in fact seems to be the current state of affairs.
In fact, if we assume God exists and is actively in communication with humans, its actually a bit weird that different human cultures would have different conceptions and names for that being. Why didn't it just give everyone the same name and information?
To answer the question of why humans give name to God. It's to make god more relatable so that they can workshop it. And use devotion to come closer with it. Look up Bhakti Yoga.
Now, you cannot worship consciousness as humans because it's invisible and you can never imagine it. You need a version of consciousness that you can see as well as you can relate to. So cultures invent localized version of God which people can relate to. And of course it will have attributes similar to that of the culture. But the properties kind of still hold. Like all knowing, powerful etc.
I've always thought arguments like these are unnecessarily applying a term loaded with human conceptions and biases in a way that doesn't shed any further light on the thing it's applied to. Like, what do we gain by defining "God" as consciousness? Why can't we just say "consciousness"? And is it worth the added confusion that when we say "God", we now don't mean what most people think "God" is?
The only reason I can come up with to do this is discomfort at saying, "I don't believe in God."
If the only common factor is a belief that 'something' created 'something', you're really not saying anything worth evaluating.
People hate not knowing the answer to the big questions so much that they'll readily accept whatever answers are served up to them.
> This like saying which Sun? Surya, Ra or Helios?
The difference is that the sun is readily observed. A conveniently invisible god isn't.
> All are different names of sun. But there is only one sun.
And there's only one human nature, which is why it's not surprising that common artefacts of human nature (e.g. religion) emerged universally throughout ancient human cultures.
But ego and names are made up. Separation just thoughts. The more life believes in thoughts it becomes divided.
But the waves and ocean are one.
You can declare Life to mean the complex interplay of every living organism, but I don’t see how you can go as far as to claim our physical and mental separateness is not there at all? After all, we need boundaries between „us“ to not be utterly alone. I like to think even of „my“ body more as a federated system, like Life maybe but on a smaller scale. I have some influence on it but not full control. In fact, one could say the polarities in the physical realm are Nature (towards separation, entropy; Kaos) and Life (actively working towards one, requires energy to keep matter ordered; Order).
If we merge, by definition the „I“ and „you“ have to die; both of us stop existing. The merger creates something new, a „we“. A single entity. We can then use the definition of identity to call this new we „I“. Rinse and repeat until back to being alone/all-one?
Do you really want to be all-one? Omnipotent, full of all potentials/possibilities? I don’t know. I am already overwhelmed with my limited human potential/possibilities/options. And I prefer to not be alone. I prefer to stay separate, and keep my identity.
I believe (lowercase b) in all sorts of stuff, scientific and otherwise, but believing in God typically indicates some kind of act of faith, which is to say, ultimately, to believe in something despite the absence of evidence for it and for some deeper reason than can be furnished by a warrant of some kind. I can believe in the spontaneous generation of the universe in the lowercase b sense of the word without really having anything to do at all with the latter kind of belief, which I think is kind of dumb.
https://www.vatican.va/content/pius-xii/en/encyclicals/docum...
> General relativity also predicts that the initial state of the universe, at the beginning of the Big Bang, was a singularity of infinite density and temperature.[6][obsolete source] However, classical gravitational theories are not expected to be accurate under these conditions, and a quantum description is likely needed[7].
https://en.wikipedia.org/wiki/Gravitational_singularity
I didn't know but apparently wikipedia treats old sources as obsolete, doesn't matter if there's new information or not that would make it obsolete.
I wonder if any sources supporting the notion that the earth is round must be updated every couple of years with a new source or study.
As an aside, the earth is almost flat, just not nearly as flat as the Universe.
Source? And make sure to update your response every few years.
https://en.wikipedia.org/wiki/The_Last_Question
Thus, anything and everything you've heard about what is there "before the big bang" has always been speculation. I mention this because sometimes people read the science media, which is always reporting on this speculation, and think that the reporting on the speculation constitutes "science" constantly changing its mind, but that's not the case here. Science has consistently not had a justifiable position on this topic, ever. It has always been speculation. It is the press that often fails to make this clear and writes stories in terms of what "science" has "discovered", but any claims of certainty in this area are not the claims of "science".
We went from thinking the Earth was the center of the universe, to the sun being the center of the universe, and the next obvious step is our universe isn't at the center of universes.
If the universe is curved dark energy is still a problem because the expansion is getting faster and overcomes the current curvature bounds.
(the basic idea was fecund universes/cosmological natural selection[1], such that we should expect to find ourselves, if the theory were true, very near to a local maxima of values such that they approximately maximize the number of black holes produced... but most of the book is really taken up with a fascinating look at the history of physics and ideas...)
[0]https://en.wikipedia.org/wiki/The_Life_of_the_Cosmos [1]https://en.wikipedia.org/wiki/Cosmological_natural_selection
* Not a physicist so this is a really uninformed take
Does it also follow that black holes in our universe contain universes internally, beyond their event horizons?! Seems like it should. Mind-blowing.
https://en.wikipedia.org/wiki/White_hole#Big_Bang/Supermassi...
It’s holes all the way down
Not necessarily. It's not clear that any are massive enough to cross the threshold required for the "bounce."
I'd love the idea that we are living inside a black hole, which is inside a black hole, which is inside a ...
There's a reason some of the most famous mathematicians, scientists, engineers, and philosophers of all time believe(d) in God.
The Hebrew name of God, YHWH, literally means "He Who Is." In other words, the Self-Existent One. The father and originator of all things that were, are, and will be, who exists outside of spacetime.
Who Created God? No one? Why does the universe need a creator if God does not?
Where does free will and evil come from if God is "originator of all things that were, are, and will be". For true free will to exist it must have a source of entropy which denotes something outside of Gods control and design otherwise everything is deterministic as set forth by God.
There are countless other religions that believe in a deity who created the universe. These deities either created themselves, or had always existed outside of space and time. To that end, any one of those deities would be on equal footing with YHWH. I don't think that it is appropriate to axiomatically claim that a certain deity exists because only that deity could have caused the universe to exist.
Why Christianity then, over Hinduism? Why any human religion at all?
[無] https://en.wikipedia.org/wiki/Trinitarianism_in_the_Church_F...
I like to think he was referring to computation. There's a reality to the constant pi, its computation, and ourselves and the representation being part of that same universe.
That reason being that for much of Western history if you didn't believe in God the Church would burn your research in a big fire and probably you on top of it.
I definitely didn’t understand whether this is suggesting that expanding universes can be contained within black holes that look like fixed-size finite objects from the outside.
And what happens to the inner universe when the parent black hole evaporates through Hawking radiation?
I've often wondered about this. I don't have any direct physics training, but it's something that felt really plausible after I learned that the mass of a black hole is linearly proportional to its swarzschild radius.
As the size of the black hole goes up, its overall density must decrease. Combined with the other observation that our universe has uniform density at large scales, it seemed really obvious to me that there existed some threshold at which the decreasing density of a very large black hole, and the fixed density of our observed universe.. would cross.
I used to muse about this question with some other tech colleagues that liked talking about physics stuff but never really got a clear answer to this.
On a side note - I'm absolutely fascinated by the implications relating to this. I'll post a follow-up thought I'm hoping somebody else has also thought about:
I've seen discussion of dark energy mostly presented as a surrogate for real energy. That there is some underlying energy "accelerating things away from each other".
I always felt uncomfortable with that characterization. It seems more reasonable to me to think of dark energy as _negative energy_ - i.e. a loss of overall energy.
In a classical system, two things moving away from each other stores potential energy that can be recouped at some later time. Dark energy doesn't work this way - things accelerate away from each other the further apart they are. From a global perspective, it's an energy loss.
The energy loss pervades to the quantum world as well - photons that start off high frequency arrive low-frequency.
It somehow feels more appropriate to me to think of dark energy as energy being extracted out of the universe, in some form never to return. Maybe like a black hole evaporating as observed from the inside?
When I asked this of some people in real life, I was pointed to answers that indicated that the "energy" component in dark energy is normalized into the "tension" of space somehow. As I mentioned before I'm not really studied in physics, but that explanation felt unsatisfactory to me.
I think my estimate came out to less dense than the required threshold but it was a while back now and cobbled together with some queries to wolfram.
But in this story the black hole increases in size as matter falls into the horizon and shrinks as it evaporates, so cosmic expansion would be associated with more energy falling into the black hole than leaving it.
Apparent distance is something that's affected by relative frames of reference and the frames of reference are as different as as can be in this case.
So time in the void between galaxies is moving quicker than time in the galaxies, but on the grand scale of the universe the differences as up a lot.
I quite liked this theory, think is make sense, at least from my very limited understanding of this stuff.
Another layman's thoughts: Isn't the energy theoretically lost by black holes so faint it's currently undetectable? And isn't the amount of dark energy theorized to be the major component of the observable universe? It seems like the numbers wouldn't add up?
I'm gonna pull out my lay understanding again. An evaporating black hole, as it gets smaller, should get more dense and be associated with a higher local spacetime curvature, no? The effect of which would be to slow down apparent time for observers within the system. Maybe that affects observed distance and rates of speed at which things seem to be happening when we look out into the sky?
Sometimes I regret not caring enough about calculus in university.
s/has/had at the time of recombination
It is largely an assumption of LCDM that we can treat the universe as practically homogeneous throughout its entire evolution but potentially not a very well-founded at that [0, 1].
> I always felt uncomfortable with that characterization. It seems more reasonable to me to think of dark energy as _negative energy_ - i.e. a loss of overall energy.
Your intuition is correct. If the Lambda term in the Einstein field equations is moved over to the side of the energy momentum tensor, it takes on the role of a negative contribution (provided Lambda > 0, as observations seem to indicate).
> In a classical system, two things moving away from each other stores potential energy that can be recouped at some later time. Dark energy doesn't work this way - things accelerate away from each other the further apart they are. From a global perspective, it's an energy loss.
Note that there is no global energy conservation in General Relativity[2], only at a local scale[3]. Heck, you'll already struggle to define what the energy is of a given piece of spacetime in a meaningful and generic manner[4, 5]. In other words, violations of energy conservation due to spacetime expanding or contracting (a strictly non-local phenomenon), like in the case of the cosmic redshift, are expected and our intuition from classical mechanics only takes you so far.
> It somehow feels more appropriate to me to think of dark energy as energy being extracted out of the universe, in some form never to return.
Dark energy aka the cosmological constant term in the Einstein field equations is a constant term, as the name suggests. Yes, there can be energy loss due to spacetime expanding (see above) but that doesn't change the gravitational constant.
[0]: https://en.wikipedia.org/wiki/Cosmic_web
[1]: https://en.m.wikipedia.org/wiki/Inhomogeneous_cosmology
[2]: https://en.m.wikipedia.org/wiki/Conservation_of_energy
[3]: https://en.m.wikipedia.org/wiki/Stress%E2%80%93energy_tensor
[4]: https://arxiv.org/abs/1510.02931
[5]: https://en.m.wikipedia.org/wiki/Mass_in_general_relativity
The center of a black hole is infinitely dense. That's why it even exists. The event horizon is not the black hole.
> and the fixed density of our observed universe
Our universe is expanding. It's density is not fixed.
You really want to be thinking about this in terms of entropy and not matter.
Arguing semantics is rather boring when it's obvious you understood the point he was trying to make.
> Our universe is expanding. It's density is not fixed.
None of that precludes uniform density at large scales.
Wouldn't you notice that fairly suddenly everything's getting brighter because all the light/radiation is sucked back in?
For smaller BH, the gravity gradient is higher and it would be detectable.
> None of that precludes uniform density at large scales.
According to observation, the universe is expanding. An argument that it's really static at a large scale would require contradicting observational evidence, but none exists. A theory that requires abandoning observational evidence bears a special burden, which this theory lacks.
And whether the density is fixed over time or not doesn't affect the question. Let's take the universe at its current average mass/energy density - whatever the "true" measure of that is.
To the best of our understanding, at large scales the density is uniform. So if we consider a suitably large spherical volume of space within our (presumably infinite) universe.. that volume will have an average mass/energy content greater than the threshold amount for a black hole of that apparent volume (again, using the external event horizon frame).
So that suggested to me that either we live in a finite universe, or we must be on the inside of an event horizon. It seems like an unavoidable conclusion.
> The center of a black hole is infinitely dense. That's why it even exists. The event horizon is not the black hole.
>> and the fixed density of our observed universe
> Our universe is expanding. It's density is not fixed.
These are both correct and germane points. So why was this post downvoted? Physics isn't a popularity contest, it relies on evidence.
The size and density of the Schwarzschild volume is determined only by mass (stationary, non-rotating). It's proportional to the inverse square of mass. Density = 3c⁶/32πG³M².
SMBHs have densities ~0.5 kg/m³ between thin air and water.
Stellar BHs are ~1e19 kg/m³ several orders of magnitude more than a neutron star.
Since we don't have a blackboard in front of us to interact with, I can suggest Alan Guth's lecture notes on Newtonian cosmology. (Guth is credited with discovering cosmic inflation.) https://web.mit.edu/8.286/www/lecn18/ln03-euf18.pdf See around eqn (3.3). You could also borrow a copy of Baumann's textbook <https://www.cambridge.org/highereducation/books/cosmology/53...> which studies the Poisson equation for various spacetimes, however a static spacetime gets most of the focus.
A universe which expands forever, or which expands faster in the later universe, makes a mess of this sort of approach to calculating a gravitational potential energy. So does any apparent recession velocity that's a large fraction of c (inducing significant redshift, whatever the recession (pseudo-)"force" might be).
However, the general idea is that there is a relationship between the kinetic energy a receding galaxy (in a system of coordinates -- a "frame" -- in which these kinematics appear) and a gravitational potential energy still occurs in a non-recollapsing universe. It's just that the potential energy climbs forever, and you get an equivalent to gravitational time dilation between galaxies at different gravitational potentials (i.e., between early-universe galaxies and higher-potential modern-times galaxies).
Accelerometers in galaxies will not show a cosmic acceleration for any galaxy; they're all really close to freely-falling (local galaxy-galaxy interactions are real -- collisions and mergers and close-calls happen -- but wash out over cosmological distances; look up "peculiar velocity" for details). Therefore we can conclude that there's no real force imposing acceleration on the galaxies. However that's also true of a cannonball in a ballistic trajectory, including one on an escape trajectory or one that enters into a stable orbit. Consequently one can draw some practical comparisons between a ballistic launch from Earth into deep space and galaxies spreading out from an initially denser early part of an expanding cosmos.
> Dark energy as energy being extracted out of the universe
No, it's just a way of thinking about whatever is driving the expansion, and that doesn't dilute away with the expansion as ordinary matter and radiation does. It's not even a "real" energy in the sense that it is only an energy in the cosmological frame, and is a frame-dependent scalar quantity, whereas in the fuller theory it's just a multiplier of the metric tensor. So it's the full relativistic metric doing the work but we absorb some of that into cosmological coordinates in the cosmological fram...