> There’s another way in which the giant firecracker idea misleads us, because even scientists often talk about the “universe springing into existence.” Well, it didn’t, as far as we can tell. The opposite is true. There is no first moment of time, just as there is no smallest positive number. In physics we have equations and laws of nature that describe how one situation changes into another, but we have no equations that show how true nothingness turns into somethingness. So, since the universe did not spring into existence, it has always existed, though perhaps not in its current form.
Or the equations are only approximations that hold under certain conditions?
Yeah this is kind of a laughable position in the article. I don’t mean the conclusion, which might be right, but the method. The laws of physics as we know them are just reflections of … nothing more than what we know. The fact that we have no account of what came before the big bang is not evidence of anything except that we don’t know, especially when a very plausible theory is that what came before is totally different in kind than what came after.
Being a good scientist doesn’t mean you’re a good philosopher.
Suppose you have a "working theory" about how birds fly, but no theory about other things might hypothetically fly. Does that afford you to claim "Nothing other than birds can fly"?
No, he proved that under existing axiomatic systems, there are some statements which cannot be proven to be true axiomatically, even though they are true; such axiomatic systems are, in his terminology, incomplete. A subtle but important difference.
One thing I've always wondered is if there's any _interesting_ statements that can't be proved or if they're all kind of self-referential nonsense statements.
Is that the kind of statement Godel was talking about? Seems to me to be somehow different. It's not really true or false, it's an arbitrary choice, so it's just something you either decide is part of your system or not, not a true statement that's unprovable.
Axiom of choice isn't really relevant to Godel's work, except for the fact that it's part of axiomatic systems. But in response to your comment, I was pointing out that there's lots of interesting math that comes from the results of his work; namely under different axiomatic systems you can find different and interesting results.
On the one hand, I've often understood that it would be nice if we could assemble a list of "all the axioms" and prove it's consistent - at least that's how it was presented to me and roughly my interpretation of what eg. Russell and Whitehead were trying to do before being derailed by Godel proving it's impossible. On more recent reflection, it seems a little silly to want a proof in system X of the consistency of system X, even before we get to Godel, because if system X is inconsistent then it can definitely provide a proof that it is consistent by the principle of explosion.
also, that his proof exists within an axiomatic system but IS ONE of its provable statements, is wildly crazy genius weird 'serendipitous' math...?! shows that at least for the boundary beyond the provably meaningful, we can still 'talk' about or 'point' at the unknown and say things like 'hey, over there is something we cannot really know nor talk about
It's not laughable at all. Before the existence of our universe, there was no time. Time was created along with the space, matter, and energy when the thing "sprang into existence." It's not valid to extrapolate backward to a time before our universe existed. This is a concept that I've tried to explain to others for years, but it's difficult for most people to grasp.
We have an accepted standard model. 2 in fact. QM and Lambda CDM say very little about how things were working very close the t=0, and say absolutely nothing about how the conditions were a t=0 or "before".
As I said in my comment, people suggest ideas of how things could be. But nothing tangible, nothing ever included in ΛCDM, nothing predicted by QM… we are missing data, solid math, and solid physic to postulate anything about t<=0. I mean … we don't even know how gravity works in these conditions. How could we even say anything about time!
> Q.E.D.
I would classify your previous comment as pseudo science, and saying "it's difficult for most people to grasp" as lack of humility.
If you do understand how space and time were structured "before the existence of our universe", you should go claim a Nobel price.
Time, as component of the universe, itself "sprang into existence?"
Despite "sprang" being a fantastical word to use in this context, it at least carries with it one thing for sure: a temporal component. "Springing" on its own indicates some sort of motion, which can only take place in time. Furthermore, "sprang" indicates a past tense, so that this "springing" took place at some (primordial) moment in time. According to your account, time presupposes itself.
You're applying the terms of experience to non-experience. The error is in a sophism of figure of speech.
Unfortunately you haven't explained anything at all. All you've demonstrated is that Kant was justified in writing the Antinomy.
Did you read the article? I put "sprang" in quotes for a reason. Speech (and writing) is how we express ourselves, but our languages are biased by the experience of our forebears, and linear time is a part of that bias.
> Before the existence of our universe, there was no time.
This is just a logical error. Unless you're using "before" in some novel way that needs clarifying.
To be clear: The author is saying that the universe has no beginning in time (and no outer bound of space). Once you remove your logical error of presupposing time before time, you are saying that the universe has a beginning in time (and presumably is enclosed within spatial bounds).
Is this not what you're saying?
The esteemed author, in saying confidently that there is no "before" the universe because the universe has no beginning, falls into the same trap that you do but lands on the other side of Kant's Antinomy: the author takes the empiricist stance in the dialectic, and you take the dogmatic stance. But even so, at least the author's stance is amenable to the infinite empirical regression of scientific practice; your stance just "puts speculative reason to slumber."
"Before the existence of our universe, there was no time."
It seems almost impossible to avoid this sort of thing (~omniscience), at least when discussing certain topics, but it can be a lot of fun to try. Noticing it in others when reading comments is much easier, and a good form of practice.
As just one more computer programmer mouthing off about a Nobel Laureate's assertions in the grand tradition of HN:
I find it far more useful to think about boundary cases like "first time" or "farthest distance" in terms of observable causal structure: what can currently know about the cause and effect relationship between things, what could we possibly know, and what could we never know? Outside of that it seems to be not only a slippery but also a steep slope into sloppy analogy to human experience.
> Or the equations are only approximations that hold under certain conditions?
Well, clearly that's possible. What is it with people on HN coming up with "gotchas" regarding topics they know nothing about?
He didn't say there could not ever be equations that show "nothingness turning into somethingness", all he says is that we have no way of showing it with what we know, what we can deduce, and much less what we can prove. If there are equations that satisfy the constraints, we're not aware of them yet (the same way we don't know yet how to combine general relativity and quantum mechanics). According to our current understanding, "the universe did not spring into existence, it has always existed, though perhaps not in its current form".
If you want to suggest random ideas, maybe you want to back them up with more than just "but what if they do exist?"
I know the models treat time as a real number that we can do funky things with (see also Banach-Tarski), but I really wonder if time isn't quantized like so much else in QM.
You might enjoy Time Reborn[1] by Lee Smolin or About Time[2] by Paul Davies. Note that the latter book is fairly old now (from 1996 or so) and I'm not sure how well it holds up now.
> even though there’s no first moment of time, we can still measure the age.
This seems to be a contradiction? The time that's passed since some kind of transformation, but not the age? What is the age of something that has no beginning?
You can still take limits as the Big Bang is approached, even if the limiting case of the Big Bang itself can never be reached. Just as you can take limits of things as some positive parameter approaches zero even if the parameter never actually takes the value zero.
I felt similarly. Thinking through the article's comparison between first moment in time and "smallest possible positive number", maybe it's sensible...
> even though there’s no first moment of time, we can still measure the age.
> even though there’s no first [positive number after zero], we can still measure the [range between zero and one].
That second variation doesn't seem so contradictory, so maybe the original isn't :)
The second variation does not seem equivalent to me. If there's no "first moment of time", you should be measuring the [range between negative infinity and one]. Using a fixed point like "zero" is the same as assuming there _is_ a first moment of time.
I'm a perpetual noob at this topic, so might be completely wrong, but: what I vaguely got from Hawking's books is that both black holes and the before-bang universe have matter in some kind of quark soup, in which our conceptions of space and time just don't exist. Since our spacetime depends on the non-soup layout of matter, the spacetime can be said to exist only with the universe after the bang (and until the crunch, if it comes). That's the age of the universe that we can reason about.
Curiously, Hawking still relates the hypotheses that (very roughly) calculate some kind of time that it would take for the soup to form into the proper universe—via Hilbert's spaces of configurations. I.e. these theories somehow count possible arrangements of matter in the soup, in the absence of space, and its movements from one arrangement to another, in the absence of time. That confuses me to this day.
Not only might there not be a first moment, there might be no time at all. Every possible instant of time could be randomly distributed with some very small but not infinitely small probability of occurring. On an infinite timeline, everything should occur, forever. When a moment occurs, a structure of your brain exists coded with memories of past events that feel real but never happened.
Since each moment is pure and has no external state, you do not perceive the trillions of years that could pass in between two moments occurring, nor do you have any way to realize you are perceiving moments out of order or that other possibilities of realities exist.
> you do not perceive the trillions of years that could pass in between two moments occurring, nor do you have any way to realize you are perceiving moments out of order or that other possibilities of realities exist
This is intriguing. But how does cause and effect work? If there is no “external state”, say I burn my hand by spilling hot coffee on it. There’s a burn in my skin. Trillions of years pass and I experience the next moment… with burned skin?
The next moment is generated entirely by chance. A very small probability. Also it could have been generated even before you spilled your coffee but you wouldn’t know that as you only have your memories as a reference. It’s like creating a movie by just putting down random pixels and eventually you get an actual frame from the movie. Repeat until the movie has been seen entirely.
There is no cause and no effect, as far as I understand it. “You” spend most of the time in bizarre states and only once in a 10^^^^^^(…)^^^^^10 seconds chances can reconstruct the next, previous or just different step of a reasonable continuous experience, including all memories “you” “think” about in this moment.
But in my opinion this is overengineered. States not only don’t have to come in order, they don’t have to form a continuous “movie” at all. An infinite amount of “current” moments with all the past and current reality already embedded in is sufficient.
”The observable universe was once compressed into a volume the size of a golf ball, but that golf ball was only a tiny piece of a universe that was infinite even then.”
What a helpful way of thinking about it. I’m surprised I’ve never heard this before. Mind expanding, no pun intended.
Rather the opposite for me, I'm now even more confused about what was where. Not that I quite get the picture of an infinite universe anyway, which I guess is the prerequisite here.
Agreed, so helpful! There's logical traps one can easily fall into (I frequently realise I'm making this mistake when trying to think of the concept of the universe) where my mind seems to want to be able to 'enclose' the universe as if it were an object so it can be referred to, like a golf ball. But I understand the concept to mean everything, all objects/information, no exceptions, and then the idea of anything outside that becomes problematic, but the golf ball is only the light that has reached us so far, and maybe the universe is really spatially infinite outside that too? How could we find out? Fascinating! great read!
I'm going to skip the more philosophical part of your question. Or in other words, if you're asking, "is there any observable evidence of something outside the observable universe?" My answer is: no comment at this time.
If you're asking, "what did John C. Mather mean in talking about the edge of the universe?" I'm not John C. Mather, but here's my guess --
The curvature of the universe [1] has been computed from distortion of the Cosmic Micrwave Background and independently using other measurements.
The current consensus is that the universe is indistinguishable from a flat universe. [2]
A curved universe would have an edge, meaning there's a limit to how much could be observed. If it's x light-years until you wrap around the universe, then plant an observer into this universe at a time greater than x years and that observer (if lucky) could observe the same things in two directions by seeing "all the way around the universe."
A curved universe might lead to a "big crunch" since the curvature of space-time is caused by the quantity of matter, or not. Depends on if the matter is tightly packed enough.
A flat universe has no limit -- no matter how far in the future you plant an observer, the speed of light is not fast enough for them to observe the entire observable universe.
There's a relationship between the curvature of the universe, how dense the universe is (how densely packed the matter is), and how fast the universe is expanding (the Hubble Constant). It's likely the universe is flat, implying that the Hubble Constant is on the high end of possible values.
> no matter how far in the future you plant an observer, the speed of light is not fast enough for them to observe the entire observable universe
I'm guessing it's just ‘universe’ here, instead of ‘observable universe’—since afaiu the definition is that light inside the observable universe is able to reach us?
So, if I understand the whole comment right, a curved universe is guaranteed to have an edge, but with a non-curved one it's a toss-up because no one knows what it would look like.
Then, when the article says:
> It’s often said that the whole universe we can now observe was once compressed into a volume the size of a golf ball, but we should imagine that the golf ball is only a tiny piece of a universe that was infinite even then.
Does the author essentially mean that the smaller universe still had only a part of it observable? Or am I mixing things up here? In fact, if the universe expanded faster in the early days, I would guess it was less observable than now (even disregarding all the matter getting in the way).
> if I understand the whole comment right, a curved universe is guaranteed to have an edge, but with a non-curved one it's a toss-up because no one knows what it would look like.
A curved universe doesn't "have an edge," I'm referring to Euclidean and non-Euclidean geometry [1]. As in, if the curvature is truly and perfectly zero, then the space-time we live in goes on forever. If it has even the tiniest curvature, then it curves back onto itself and is non-Euclidean.
If it is truly and perfectly zero, then all I'm trying to say is that it goes on forever like an "ideal" 2D plane or 3D space.
Ah, indeed, quite a brain fart moment from me there, since you explained the structure right in the previous comment. Pondering cosmology while sleep-deprived is suboptimal, I guess.
Though now I'm curious about this:
> If it has even the tiniest curvature, then it curves back onto itself and is non-Euclidean
Would it be possible in theory that the three dimensions are curved like a helix—so they have constant curvature but don't intersect themselves? This way the universe would still stretch infinitely in most directions, but would be non-Euclidean, and you'd need to know where the ‘axis’ is to be able to see in a direction that shortcuts to another one.
Just hypothetical 3D curved spaces here, not saying this has any physical reality -
If the X axis curves into Y (i.e. wraps around the Z axis) and also has a slight negative Z component (i.e. to move in a helical fashioin) each of those curvatures would mean a line segment eventually intersected itself.
It's the nature of the curvature: the space is not sheared (like a rhombus), it is curved (like latitude and longitude), which is why the line segment eventually intersects itself.
> Does the author essentially mean that the smaller universe still had only a part of it observable?
No, I think John C. Mather there is focused wholly on the concept of infinity. So even if the whole observable universe (30 billion light-years across) got squished to the size of a golf ball, the whole universe (infinity light-years across) would still be infinite, because multiplying infinity by some small constant still equals infinity.
> Is it the redshift receding into infinite wavelengths?
On further thought, things redshifting away into the blackness just denote the edge of the visible universe, don't they? Since that's where light has trouble ever catching up with us, instead of being carried away by the expansion. So this isn't quite related to the universe being infinite or not.
What's the reasoning behind that? Because I feel the other way: for me, it's much harder to accept the idea that the Big Bang that spawned our universe was a singular event, because that would mean that there is only one inevitable end: heat death. And even though it's unlikely the human race will still be there by that time, I don't like the prospect of such a pale and bleak ending.
If, on the other hand, you assume that there was some form of time/matter before the Big Bang, there is no reason to assume that there can be (or has been) only one big bang event. And that means there might be a multitude of "universes" outside of our visible field that we can never know about. Still, it's oddly comforting to me to believe that when our universe dies from heat death, others might go still on or start a new cycle.
The way I understand it, time is defined in terms of entropy- the points in the space of configurations of the universe adjacent to ours are all possible, but the ones that are most likely are all possible future points and the ones that are least likely are points in the past. Entropy is always increasing, on the macro scale. (The past, like the future, is uncertain and there could be many past states leading to this point.)
But, in the early early universe, all the configurations are equally likely, or rather there are no points any more unlikely, so there is no past, every direction is the future.
That’s not very precise but basically as I understand it that’s why there is no earliest moment.
Yes but it wouldn’t matter because for us it’s strictly equivalent to experiencing time linearly. That’s the epistemological limit of science. Physics don’t concern itself with truth, only empirical evidence and models.
That’s also why for all his brillance John C. Matter is very wrong here. "[…] we have no equations that show how true nothingness turns into somethingness. So, since the universe did not spring into existence, it has always existed, though perhaps not in its current form." is a conclusion which doesn’t follow from its premise. We just have no idea and no way to test anything.
There is no time, only movement. No movement == no time. You can't measure time without movement. If everything in the universe stopped moving, no time would pass.
The first moment happened when space was created and something in it changed its position.
(Of course, that something is matter, which is just a wave, and a wave by definition is movement... So really, time started when reality started wobbling.)
I never heard of him before! He was definitely into wiggles. And psychedelics apparently.
> "But the real world is wiggly, wiggly, wiggly. Now when you have a wiggly system like a cloud, how much wiggle is a wiggle? Well, you have to draw the line somewhere. And so people come to sorts of agreements about, uh, how much of a wiggle is a wiggle; that is to say a thing. One wiggle, you can always reduce any one wiggle into sub-wiggles. Or see it as a subordinate wiggle in a bigger wiggle. But there’s no real fixed rule about it.”
He and Schrödinger would have had a blast together.
Does anyone know how the validity of a linear extrapolation is determined? I mean is there a standard way of measuring an extrapolation, like sigma? The only way I can think of is to take the ratio of the sample with the population. For instance, if sample = 24 and population = 200 billion, their ratio is 0.00000012. How do we know if this is a valid linear extrapolation? In this case, sample is the number of galaxies Hubble observed in 1929 for his famous paper and the population is the number of known galaxies. Is there a rigorous way to evaluate an extrapolation in statistics?
This feels kinda like that… Certainly "time" passes, but if nobody is measuring it (or even conceiving of it as "a thing") at what point is it relevant in any way?
I certainly have vague ideas about how it works, but it feels like some physicists feel that time is emergent too. Even if not true, consider this thesis: There is no time at all, not before BB, not after. We only “see” our time because it is a consequence of non-euclidity of what we call spacetime, which is otherwise a timeless structure in which one could recognize “entropy” vectors. Then our emergent time could not exist before BB. And when you apply “exist” or any other temporal tense to that structure as a whole, it’s just a semantic error.
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[ 2.3 ms ] story [ 139 ms ] threadOr the equations are only approximations that hold under certain conditions?
Being a good scientist doesn’t mean you’re a good philosopher.
Suppose you have a "working theory" about how birds fly, but no theory about other things might hypothetically fly. Does that afford you to claim "Nothing other than birds can fly"?
In physics maths always go haywire durnig phase changes, as gas laws don't apply to liquids, and such.
Maybe I'm missing something?
We don't know that.
> Time was created along with the space, matter, and energy when the thing "sprang into existence."
These are just speculations. Some theories indeed mention that, but they are not part of our standard models.
For now, we just don't know.
> it's difficult for most people to grasp.
Oh come on…
Yes we do: https://www.britannica.com/science/space-time
> it's difficult for most people to grasp.
"Oh come on…"
Q.E.D.
I don’t see anything in that article mentioning that time did not exist before the universe existed. Did I miss it?
We have an accepted standard model. 2 in fact. QM and Lambda CDM say very little about how things were working very close the t=0, and say absolutely nothing about how the conditions were a t=0 or "before".
As I said in my comment, people suggest ideas of how things could be. But nothing tangible, nothing ever included in ΛCDM, nothing predicted by QM… we are missing data, solid math, and solid physic to postulate anything about t<=0. I mean … we don't even know how gravity works in these conditions. How could we even say anything about time!
> Q.E.D.
I would classify your previous comment as pseudo science, and saying "it's difficult for most people to grasp" as lack of humility.
If you do understand how space and time were structured "before the existence of our universe", you should go claim a Nobel price.
Despite "sprang" being a fantastical word to use in this context, it at least carries with it one thing for sure: a temporal component. "Springing" on its own indicates some sort of motion, which can only take place in time. Furthermore, "sprang" indicates a past tense, so that this "springing" took place at some (primordial) moment in time. According to your account, time presupposes itself.
You're applying the terms of experience to non-experience. The error is in a sophism of figure of speech.
Unfortunately you haven't explained anything at all. All you've demonstrated is that Kant was justified in writing the Antinomy.
> Before the existence of our universe, there was no time.
This is just a logical error. Unless you're using "before" in some novel way that needs clarifying.
To be clear: The author is saying that the universe has no beginning in time (and no outer bound of space). Once you remove your logical error of presupposing time before time, you are saying that the universe has a beginning in time (and presumably is enclosed within spatial bounds).
Is this not what you're saying?
The esteemed author, in saying confidently that there is no "before" the universe because the universe has no beginning, falls into the same trap that you do but lands on the other side of Kant's Antinomy: the author takes the empiricist stance in the dialectic, and you take the dogmatic stance. But even so, at least the author's stance is amenable to the infinite empirical regression of scientific practice; your stance just "puts speculative reason to slumber."
And yet, you've managed to do just that!
> This is a concept that I've tried to explain to others for years, but it's difficult for most people to grasp.
Not surprising since not all people experience the same reality.
How?
It seems almost impossible to avoid this sort of thing (~omniscience), at least when discussing certain topics, but it can be a lot of fun to try. Noticing it in others when reading comments is much easier, and a good form of practice.
I find it far more useful to think about boundary cases like "first time" or "farthest distance" in terms of observable causal structure: what can currently know about the cause and effect relationship between things, what could we possibly know, and what could we never know? Outside of that it seems to be not only a slippery but also a steep slope into sloppy analogy to human experience.
Well, clearly that's possible. What is it with people on HN coming up with "gotchas" regarding topics they know nothing about?
He didn't say there could not ever be equations that show "nothingness turning into somethingness", all he says is that we have no way of showing it with what we know, what we can deduce, and much less what we can prove. If there are equations that satisfy the constraints, we're not aware of them yet (the same way we don't know yet how to combine general relativity and quantum mechanics). According to our current understanding, "the universe did not spring into existence, it has always existed, though perhaps not in its current form".
If you want to suggest random ideas, maybe you want to back them up with more than just "but what if they do exist?"
Preferably a book that’s entertaining to read rather than engrossed in mathematics
[1]: https://www.amazon.com/Time-Reborn-Lee-Smolin/dp/0544245598
[2]: https://www.amazon.com/About-Time-Einsteins-Unfinished-Revol...
This seems to be a contradiction? The time that's passed since some kind of transformation, but not the age? What is the age of something that has no beginning?
> even though there’s no first moment of time, we can still measure the age.
> even though there’s no first [positive number after zero], we can still measure the [range between zero and one].
That second variation doesn't seem so contradictory, so maybe the original isn't :)
Curiously, Hawking still relates the hypotheses that (very roughly) calculate some kind of time that it would take for the soup to form into the proper universe—via Hilbert's spaces of configurations. I.e. these theories somehow count possible arrangements of matter in the soup, in the absence of space, and its movements from one arrangement to another, in the absence of time. That confuses me to this day.
Since each moment is pure and has no external state, you do not perceive the trillions of years that could pass in between two moments occurring, nor do you have any way to realize you are perceiving moments out of order or that other possibilities of realities exist.
I can imagine scenarios where that isn’t true- maybe the universe cycles through a long loop of states and just repeats that infinitely for example.
This is intriguing. But how does cause and effect work? If there is no “external state”, say I burn my hand by spilling hot coffee on it. There’s a burn in my skin. Trillions of years pass and I experience the next moment… with burned skin?
But in my opinion this is overengineered. States not only don’t have to come in order, they don’t have to form a continuous “movie” at all. An infinite amount of “current” moments with all the past and current reality already embedded in is sufficient.
What a helpful way of thinking about it. I’m surprised I’ve never heard this before. Mind expanding, no pun intended.
How is this determined? I would think that the observable universe puts a limit on our view anyway.
Is it the redshift receding into infinite wavelengths? Can the instruments even detect this?
If you're asking, "what did John C. Mather mean in talking about the edge of the universe?" I'm not John C. Mather, but here's my guess --
The curvature of the universe [1] has been computed from distortion of the Cosmic Micrwave Background and independently using other measurements.
The current consensus is that the universe is indistinguishable from a flat universe. [2]
A curved universe would have an edge, meaning there's a limit to how much could be observed. If it's x light-years until you wrap around the universe, then plant an observer into this universe at a time greater than x years and that observer (if lucky) could observe the same things in two directions by seeing "all the way around the universe."
A curved universe might lead to a "big crunch" since the curvature of space-time is caused by the quantity of matter, or not. Depends on if the matter is tightly packed enough.
A flat universe has no limit -- no matter how far in the future you plant an observer, the speed of light is not fast enough for them to observe the entire observable universe.
There's a relationship between the curvature of the universe, how dense the universe is (how densely packed the matter is), and how fast the universe is expanding (the Hubble Constant). It's likely the universe is flat, implying that the Hubble Constant is on the high end of possible values.
[1] http://background.uchicago.edu/~whu/beginners/curvature.html
[2] https://astrobites.org/2020/12/03/cosmic-clocks/
> no matter how far in the future you plant an observer, the speed of light is not fast enough for them to observe the entire observable universe
I'm guessing it's just ‘universe’ here, instead of ‘observable universe’—since afaiu the definition is that light inside the observable universe is able to reach us?
So, if I understand the whole comment right, a curved universe is guaranteed to have an edge, but with a non-curved one it's a toss-up because no one knows what it would look like.
Then, when the article says:
> It’s often said that the whole universe we can now observe was once compressed into a volume the size of a golf ball, but we should imagine that the golf ball is only a tiny piece of a universe that was infinite even then.
Does the author essentially mean that the smaller universe still had only a part of it observable? Or am I mixing things up here? In fact, if the universe expanded faster in the early days, I would guess it was less observable than now (even disregarding all the matter getting in the way).
A curved universe doesn't "have an edge," I'm referring to Euclidean and non-Euclidean geometry [1]. As in, if the curvature is truly and perfectly zero, then the space-time we live in goes on forever. If it has even the tiniest curvature, then it curves back onto itself and is non-Euclidean.
If it is truly and perfectly zero, then all I'm trying to say is that it goes on forever like an "ideal" 2D plane or 3D space.
[1] https://en.wikipedia.org/wiki/Plane_(geometry)
Ah, indeed, quite a brain fart moment from me there, since you explained the structure right in the previous comment. Pondering cosmology while sleep-deprived is suboptimal, I guess.
Though now I'm curious about this:
> If it has even the tiniest curvature, then it curves back onto itself and is non-Euclidean
Would it be possible in theory that the three dimensions are curved like a helix—so they have constant curvature but don't intersect themselves? This way the universe would still stretch infinitely in most directions, but would be non-Euclidean, and you'd need to know where the ‘axis’ is to be able to see in a direction that shortcuts to another one.
If the X axis curves into Y (i.e. wraps around the Z axis) and also has a slight negative Z component (i.e. to move in a helical fashioin) each of those curvatures would mean a line segment eventually intersected itself.
It's the nature of the curvature: the space is not sheared (like a rhombus), it is curved (like latitude and longitude), which is why the line segment eventually intersects itself.
No, I think John C. Mather there is focused wholly on the concept of infinity. So even if the whole observable universe (30 billion light-years across) got squished to the size of a golf ball, the whole universe (infinity light-years across) would still be infinite, because multiplying infinity by some small constant still equals infinity.
On further thought, things redshifting away into the blackness just denote the edge of the visible universe, don't they? Since that's where light has trouble ever catching up with us, instead of being carried away by the expansion. So this isn't quite related to the universe being infinite or not.
If, on the other hand, you assume that there was some form of time/matter before the Big Bang, there is no reason to assume that there can be (or has been) only one big bang event. And that means there might be a multitude of "universes" outside of our visible field that we can never know about. Still, it's oddly comforting to me to believe that when our universe dies from heat death, others might go still on or start a new cycle.
It doesn’t necessarily imply heat death, especially with inflation and non zero space time energy being generated somehow.
But, in the early early universe, all the configurations are equally likely, or rather there are no points any more unlikely, so there is no past, every direction is the future.
That’s not very precise but basically as I understand it that’s why there is no earliest moment.
That’s also why for all his brillance John C. Matter is very wrong here. "[…] we have no equations that show how true nothingness turns into somethingness. So, since the universe did not spring into existence, it has always existed, though perhaps not in its current form." is a conclusion which doesn’t follow from its premise. We just have no idea and no way to test anything.
The first moment happened when space was created and something in it changed its position.
(Of course, that something is matter, which is just a wave, and a wave by definition is movement... So really, time started when reality started wobbling.)
“It’s all wiggles” —- Alan Watts
> "But the real world is wiggly, wiggly, wiggly. Now when you have a wiggly system like a cloud, how much wiggle is a wiggle? Well, you have to draw the line somewhere. And so people come to sorts of agreements about, uh, how much of a wiggle is a wiggle; that is to say a thing. One wiggle, you can always reduce any one wiggle into sub-wiggles. Or see it as a subordinate wiggle in a bigger wiggle. But there’s no real fixed rule about it.”
He and Schrödinger would have had a blast together.
https://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest
This feels kinda like that… Certainly "time" passes, but if nobody is measuring it (or even conceiving of it as "a thing") at what point is it relevant in any way?
I certainly have vague ideas about how it works, but it feels like some physicists feel that time is emergent too. Even if not true, consider this thesis: There is no time at all, not before BB, not after. We only “see” our time because it is a consequence of non-euclidity of what we call spacetime, which is otherwise a timeless structure in which one could recognize “entropy” vectors. Then our emergent time could not exist before BB. And when you apply “exist” or any other temporal tense to that structure as a whole, it’s just a semantic error.