So Hawking radiation moves the estimate from the previous 10^1100 to 10^78 years. That's a pretty drastic change, but naturally, not exactly something to go and worry about. Most of us would be lucky to make it to 10^2, so there's still some way to go.
The exponent going 1100 to 78 is pretty large error... huge 93% reduction... hopefully they have high confidence in the new value, otherwise humanity might be looking at 1 more big problem this century.
It's actually a 99.99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999% reduction and yes that is the correct number of 9's.
I started to read this book, but never finished it, but the whuffie idea has legs. Stuck with me longer than many ideas from books I did finish. Need to pick it up again.
My shower is theory is that there are infinite universes getting created all the time and we can never know about it because we're restricted in this universe. I love having these talks with my daughter.
That's almost the mainstream position in physics as of 2025 -- that cosmic inflation never stopped, that it produces universes beyond number, and we're in one pinched-off region of it.
The trouble would be that even if we sensed other universes we might not be able to go there unless we can create our own pocket universes. There's no guarantee that an adjacent universe has the same rules of physics.
All of the enzymes in your body might stop working if you stepped into even a slightly different universe. You could just turn into a gas, and not in a good way.
Huh. When I've tried to sell my soul, I was scolded that trying to sell something you don't own in the first place is bad style. Oh, and they've also changed my last name to "Asshole" in all of my papers, such pettiness :/
I wonder, is immortality a boon or a curse? So many depictions of immortality show the person suffering. At least there's an upper bound on the suffering though, only 10^78 years.
A fun tool to think around such things are Penrose diagrams. Personally I'm a little dubious of strong claims of what will happen in the distant future since we have such incomplete models of physics today. It takes GUTs to predict the future.
If there is nothing left, does time pass? Does it pass but is meaningless? Does it no longer exist?
The same question goes for space. Is there any size to the nothingness? To go further when you have notions like inflation, can you have nothing that is increasing in volume? That would suggest a change in state an thus a sense of not yet ended.
It would be a weird thing for nothingness to change state. It seems like fertile soil for sci-fi. Imagine if space itself was kind of Turing complete and once the noise of matter ended it could start the real work, which of course would be simulating the next universe.
That was kind of my intuition as well, similarly for time, if there was no distinction between long and short amounts of time, an instant would be the same as eons. If the big bang was improbable but possible it would just happen. The fact that we are here is suggestive that is possible.
I think that's it. Ad a layman I don't understand how the final transition (final hawking radiation) then tells the rest of the universe "I'm done" similar to a sprint retro!
It’s a beautiful theory, and I’d like to believe in it, but with ubiquitous virtual particles, the last particle in the universe would never be alone to reject time
That question makes no sense in terms of this discussion. The heat death of the universe means that there is no "after", just as there was no "before" the Big Bang.
The actual concept of time does not exist (at least in my humble year 12 physics understanding and having read Brief History Of Time a long time ago :) )
> having read Brief History Of Time a long time ago :)
It pains me to say this, because it is a masterpiece of vulgarisation, putting arcane physics and cosmology within reach of (still decently-educated) normal people, but it is very outdated in a lot of respects. It badly needs something else.
I found some of Carlo Rovelli’s books to be quite compelling, but they are more focused on the topic of time and space-time. Not really the universe in the same way as Hawking’s were.
The researchers calculated that the process of Hawking radiation theoretically also applies to other objects with a gravitational field
but: doesn't this only apply if these objects if they have some sort of decay process going on? There are nuclides that have never been observed decaying. I would expect a white dwarf to burn out, go through radioactive decay (unstable nuclides -> stable ones) and end up as inert rock (stable nuclides) at background temperature.
Regular "stable nuclides" stuff which falls into a black hole gets spit out as Hawking radiation, so no, this is a gravitational process, radioactive decay is a standard model one.
Hawking radiation doesn't require decay. Pairs of particles appear spontaneously. One falls into the gravitational field, losing energy.
The net energy loss comes from the gravitational field of the object, and its mass decreases. We don't have details on just what that means at a Standard Model level, but the net loss of energy means something is going to disappear even without any kind of previously understood decay.
>here are nuclides that have never been observed decaying
Aren't we pretty sure due to things like quantum tunneling that the probability of any quantum particle existing trends to zero given a long enough time?
The whole point of Hawking radiation is that a thing which famously shouldn't have a decay process (a black hole) in fact does have a decay process due to the interaction of gravity and quantum mechanics.
As someone who doesn’t know much about this, I'm curious:
If humanity survived far into the future, could we plausibly develop ways to slow or even halt the decay of the universe? Or is this an immutable characteristic of our universe, meaning humanity will inevitably fizzle out along with the universe?
While it seems doubtful that people will last that long, in 10^78 years, one would think those people alive at the time would want the universe to continue.
I think a bigger question is what will they do for that long?
All the things like stars will be long gone and dead before that time leaving us with long lived black holes and radiation. So everything would be based on virtual world can computation by that point. Do you just cool everything to near absolute zero and run it as slow as possible to you can last as long as possible?
The History of the Universe channel has an episode around this, but I'll have to figure out which one it was.
Agreed. It is so highly unlikely that the probability is effectively zero.
Let's give everyone the benefit of the doubt and assume that humanity can exist a thousand times longer than your estimate, say 3x10^9 years. That's about as long as we think life has existed on earth, which is a VERY LONG TIME. That said, it's still 1 x 10^-69 of that time period. I think you can see where we're going with this.
No offense intended, but I have a serious question:
Why would you hope this? This hope seems to me a vestige of the desire of some humans for immortality. And why would it matter to folks whether some sort of intelligence existed this incomprehensibly far into the future?
If we survive far into the future, we will learn a lot more about the structure and evolution of the Universe. It might be that the questions that our scientists can ask now will turn out to be trivial or meaningless to our descendants. Perhaps the Universe is far stranger than we can imagine.
I’m not an expert on this, but I read this by Lawrence M Krauss (theoretical physicist and cosmologist):
“In 5 billion years, the expansion of the universe will have progressed to the point where all other galaxies will have receded beyond detection. Indeed, they will be receding faster than the speed of light, so detection will be impossible. Future civilizations will discover science and all its laws, and never know about other galaxies or the cosmic background radiation. They will inevitably come to the wrong conclusion about the universe......We live in a special time, the only time, where we can observationally verify that we live in a special time.”
A billion is just 10 to the power of nine, and that number of years in time is itself a long, long time that’s difficult to imagine. Looking at 10 to the power of 78 is…it wouldn’t matter much for us if it were to the power of 60 either. (I think!) I seriously doubt humans (as we know of now) can meaningfully affect the expansion or decay of the universe.
In just 5 billion years? This surprises me, trillion I could understand, 5 billion is similar to the age of the earth.
Incidentally, the obvious counter to "our time is special, we have access to everything" is presumably what future civilisations think as well; the implication being perhaps we have lost something over the aeons that would shed light on our current mysteries.
I haven't read the book but it's an unconvincing extract, though I acknowledge a larger context may justify it.
Someone made a miscalculation with 5 billion years, but with that said, it's only just over an order of magnitude more which isn't much
>And what are presently the closest galaxy groups outside of the Local Group — objects like the M81 group — will be the last to become unreachable: something that won't occur until more than 110 billion years from now, when the Universe is nearly ten times its present age.
Maybe there was a self-conscious "civilization" before the big bang. From my understanding we know very little to nothing about anything before the big bang.
Unless you believe that this universe is just playing out holographic on the event horizon of an N+1d black hole in our parent universe. The Big Bang was just the singularity birth of that one object.
Except not all dimension numbers have nicely defined physics and geometries. For example, 4+0 and 4+1 don't have symmetric pairwise particle interactions in the sense we have in 3+1.
Right so we're limited in time and resources, in a sense. Only some of the universe would be reachable within those 10^1100 or 10^78 years anyway. So we are limited by time but also what we can access.
What's fascinating to me is to consider the frontier of galaxies theoretically reachable within a given window, and the potential race to colonize them before they race away.
Can you provide the source for that quote? 5 billion years seems way too soon.
The Hubble constant is currently approximately one doubling per 14 billion years [1]. So 5 billion years isn't enough to double the recession speeds. AFAIK there's plenty of galaxies receding at less than half the speed of light. Wikipedia estimates 150 billion years (6000x expansion) for all but the local group to be beyond the horizon [2]. So your quote seems to be off by two orders of magnitude.
Well, the rest of us will likely die. However, you (the reader of this comment) will only have observed universes in which you don’t die. So, due to quantum immortality and all that, you’ll figure it out I guess. And in some sense humanity will not fizzle out; at least you’ll carry it along.
It is a big project, but don’t worry, you’ve got quite a while to work it all out. I would start working on it in earnest in about a million years. If you wait a couple billion, more of the stuff in the universe might have decayed, and the end result might be less interesting, I guess.
Please tell whatever else is around about the rest of us!
Time is irrelevant. What matters are units of computations.
When things are predictable they can be simulated fast : A spinning ball in the void can be simulated for 10^78 years in O(1).
When things are fuzzy, they can be simulated fast : A star made of huge number of atoms is not so different than another star made of a huge number of atoms. When processes are too complex they tend to all follow the law of large numbers which makes the computations memoizable.
What you want is a way to prevent the universe from taking shortcuts in its computations. Luckily its quite easy. You have to make details important. That's where chaos theory comes to the rescue. Small perturbations can have big impacts. Bifurcations like tossing a coin in the air create pockets of complexity. But throw too many coins in the air and its just random and boring. Life exists on this edge where enough structure is preserved to allow enough richness to exist.
One way humans have found of increasing precision is the lathe, which lead to building computers. Build a big enough fast enough computer and you will run-out of flops faster than reaching the 10^78 endgame.
But you have to be smart, because computation being universal it means that if you are just building a big computer what matters will be what runs on it. And your universe can be reduced to a recursive endgame state of "universe becoming a computer running universe simulation of a specific type", which doesn't need to computed more than once and already was, or isn't interesting enough to deserve being computed.
That's why we live on the exciting edge before the Armageddon, boring universes having already been simulated. The upside being universe hasn't yet decided which endgame we may reach, because the phytoplankton aliens of k2-18b have not yet turned on their supercomputer.
Hawking radiation is a very slow process; one can acquire additional matter (e.g., hydrogen atoms from interstellar or intergalactic space) to compensate for the matter loss
Here's some food for thought: there are perhaps some things that would be perhaps out of reach for all living beings for the conceivable future and beyond.
We are barely able to handle technological progress that would seem like stone age or even worse to a potential species that may exist at that time (ie those that may have such technology to stop the death of the very universe they are living)
They might just be indistinguishable from a god if there is one. And if they have enough power to perhaps prevent the death of the universe, they might have enough technology to just recreate another one. Or open a wormhole and transport to a new one or travel the multiverse or something.
Basically I feel if such kind of technology can be created to bend the universe to your will, it would be misused so badly, it might be catastrophic for the existence of such a species.
Ok, well, surviving beyond 1 billion years and various extinction level events, asteroids, comets, nuclear wars, are are the first priority, we'll worry about this later.
Perhaps we can set up a secret program where AI randomly selects individuals based on merit, character to get the latest in life extension treatments, philosophical and spiritual education so they can guide us (with AI assistence) into the future and beyond the solar system.
If we survive, 'we' most probably don't exist by that time in any recognisable shape or form.
If only it was nukes. I'm afraid we're more likely to go out with a whimper. The fertility rates have plummeted and there's no reason to believe those will rise back to replacement level.
There is also no reason to believe that the fertility rates would go to zero. To an outside observer, we might simply be reaching a new equilibrium.
The idealized Star Trek society of production automation and exploratory self fulfillment might only be possible, and sustainable, if we are a billion people.
That is still plenty enough people to continue our ever accelerating and vast exploration of culture, science and space.
Imagine blowing up an infinitesimally small balloon. Nowhere on the surface will you find the center. Also, as the other comment says, the center is everywhere. We are on the inside of the big bang.
I suppose this time is expressed in earth years? Or what would this duration mean on a Universe scale? Also given the nature of space-time (the time and gravity relationship) wouldn't time be almost still once, let's say, year 10⁷⁷ is reached?
If you were in a place where time was still you'd have no idea it were the case. Time would still tick at one second per second. You could only tell when you looked at some other object/patch of space that had a different ticking clock.
Time is relative, absolutely (I had to do it, sorry). I guess in these articles they mean 10^77 years for an observer on earth. My understanding is if I was, somehow, waiting inside a black hole it would take much less time for me to observe the universe decaying. And if i'm not mistaken, then I wonder what does that mean for the universe as a whole. Maybe the question doesn't make sense when taking the whole universe as being the "observer"...
>Because the researchers were at it anyway, they also calculated how long it takes for the moon and a human to evaporate via Hawking-like radiation. That's 10^90 years.
Well I can predict the next trend, launching very rich people's body into space so it will last 10^90 years :)
Is it though? It is my understanding that the quantum fluctuations that give rise to BBs will still exist, even after (and specially after) the evaporation of black holes (perhaps assuming no Big Rip).
It's just a joke but the average number of years for a spontaneous quantum fluctuation to produce a boltzmann brain was calculated at something like 10^500 years. You're right that the processes involved would still remain barring some kind of big rip event.
Does this mean such an event could produce, say, an entire universe?
If so, does this theoretically mean that a cyclic universe is possible in this way, and that if one were to go far enough - impossibly, unfathomably far - you might find the remnants of other universes?
The theory of Boltzmann brains is that you're way more likely to get just a brain (including false memories of a planet earth and a whole visibile universe around it), than to get a brain, a planet earth, and a whole visible universe around it. So the chance that any of that is real, given that a brain exists to perceive it, is infinitesimal. We are probably just floating human brains that popped into the vastness of space three microseconds ago, complete with false memories of the distant past.
To dispel a misconception: They're not some hypothetical type of brain that exists as pure quantum fluctuations (though those are even more likely). Boltzmann was talking about the probability of actual flesh-and-blood human brains arising spontaneously out of the vacuum.
Wouldn’t the vast majority of those be incoherent broken messes, of various levels of inconsistency? Only a teeny tiny fraction would be coherent. So the expected experience fir any arbitrary Boltzmann brain would be all over the place.
Not a physicist, but I see it this way too. My understanding of Boltzmann brains is that they are a theoretical consequence of infinite time and space in a universe with random quantum fluctuations. And that those random fluctuations would still be present in an otherwise empty universe. So then this article has no bearing on the Boltzmann brain thought experiment or its ramifications.
332 comments
[ 4.2 ms ] story [ 298 ms ] threadI started to read this book, but never finished it, but the whuffie idea has legs. Stuck with me longer than many ideas from books I did finish. Need to pick it up again.
https://en.wikipedia.org/wiki/Down_and_Out_in_the_Magic_King...
That's some kind of typo no? I've only heard previous estimates for white dwarf to be trillions of years, that is significantly shorter that 10^1100
Edit: never mind, by lifetime that me proton decay, not how long they shine light
You'd like this book: https://mitpress.mit.edu/9780262547222/an-infinity-of-worlds...
All of the enzymes in your body might stop working if you stepped into even a slightly different universe. You could just turn into a gas, and not in a good way.
I think you've gotten away pretty well.
https://youtu.be/mht-1c4wc0Q
The same question goes for space. Is there any size to the nothingness? To go further when you have notions like inflation, can you have nothing that is increasing in volume? That would suggest a change in state an thus a sense of not yet ended.
It would be a weird thing for nothingness to change state. It seems like fertile soil for sci-fi. Imagine if space itself was kind of Turing complete and once the noise of matter ended it could start the real work, which of course would be simulating the next universe.
If there are no physical laws, there’s nothing to stop that happening.
The actual concept of time does not exist (at least in my humble year 12 physics understanding and having read Brief History Of Time a long time ago :) )
It pains me to say this, because it is a masterpiece of vulgarisation, putting arcane physics and cosmology within reach of (still decently-educated) normal people, but it is very outdated in a lot of respects. It badly needs something else.
I found some of Carlo Rovelli’s books to be quite compelling, but they are more focused on the topic of time and space-time. Not really the universe in the same way as Hawking’s were.
The net energy loss comes from the gravitational field of the object, and its mass decreases. We don't have details on just what that means at a Standard Model level, but the net loss of energy means something is going to disappear even without any kind of previously understood decay.
That's not really true. Even Hawking admitted that's it's a simplification he did for his popular science book of what really is going on.
https://www.youtube.com/watch?v=UxVssUb0MsA
Aren't we pretty sure due to things like quantum tunneling that the probability of any quantum particle existing trends to zero given a long enough time?
If humanity survived far into the future, could we plausibly develop ways to slow or even halt the decay of the universe? Or is this an immutable characteristic of our universe, meaning humanity will inevitably fizzle out along with the universe?
https://users.ece.cmu.edu/~gamvrosi/thelastq.html
Instead, its response—"INSUFFICIENT DATA FOR MEANINGFUL ANSWER"—is a model of intellectual honesty.
The first problem is data integrity and storage. Will the atoms the answer is on, still be around?
The next is, what kind of search engine will we have, with 10^78 years of internet history?!
All the things like stars will be long gone and dead before that time leaving us with long lived black holes and radiation. So everything would be based on virtual world can computation by that point. Do you just cool everything to near absolute zero and run it as slow as possible to you can last as long as possible?
The History of the Universe channel has an episode around this, but I'll have to figure out which one it was.
The World at the End of Time by Frederick Pohl.
https://en.wikipedia.org/wiki/Iron_star#Compact_iron_star_fo...
...although I'm not sure I've ever seen the expected temperature of iron stars. 1 milliKelvin?
We don't need to worry, it is highly unlikely that humanity as we recognize it will exist.
Let's give everyone the benefit of the doubt and assume that humanity can exist a thousand times longer than your estimate, say 3x10^9 years. That's about as long as we think life has existed on earth, which is a VERY LONG TIME. That said, it's still 1 x 10^-69 of that time period. I think you can see where we're going with this.
Why would you hope this? This hope seems to me a vestige of the desire of some humans for immortality. And why would it matter to folks whether some sort of intelligence existed this incomprehensibly far into the future?
https://users.ece.cmu.edu/~gamvrosi/thelastq.html
“In 5 billion years, the expansion of the universe will have progressed to the point where all other galaxies will have receded beyond detection. Indeed, they will be receding faster than the speed of light, so detection will be impossible. Future civilizations will discover science and all its laws, and never know about other galaxies or the cosmic background radiation. They will inevitably come to the wrong conclusion about the universe......We live in a special time, the only time, where we can observationally verify that we live in a special time.”
A billion is just 10 to the power of nine, and that number of years in time is itself a long, long time that’s difficult to imagine. Looking at 10 to the power of 78 is…it wouldn’t matter much for us if it were to the power of 60 either. (I think!) I seriously doubt humans (as we know of now) can meaningfully affect the expansion or decay of the universe.
Incidentally, the obvious counter to "our time is special, we have access to everything" is presumably what future civilisations think as well; the implication being perhaps we have lost something over the aeons that would shed light on our current mysteries.
I haven't read the book but it's an unconvincing extract, though I acknowledge a larger context may justify it.
>And what are presently the closest galaxy groups outside of the Local Group — objects like the M81 group — will be the last to become unreachable: something that won't occur until more than 110 billion years from now, when the Universe is nearly ten times its present age.
What's fascinating to me is to consider the frontier of galaxies theoretically reachable within a given window, and the potential race to colonize them before they race away.
That's... awe inspiring.
The Hubble constant is currently approximately one doubling per 14 billion years [1]. So 5 billion years isn't enough to double the recession speeds. AFAIK there's plenty of galaxies receding at less than half the speed of light. Wikipedia estimates 150 billion years (6000x expansion) for all but the local group to be beyond the horizon [2]. So your quote seems to be off by two orders of magnitude.
[1]: https://astronomy.stackexchange.com/questions/49248/interpre...
[2]: https://en.wikipedia.org/wiki/Timeline_of_the_far_future
Yeah, seems off. According to Wikipedia it's 2 trillion years[1] until galaxies outside the Local Supercluster become undetectable.
[1]: https://en.wikipedia.org/wiki/Future_of_an_expanding_univers...
It is a big project, but don’t worry, you’ve got quite a while to work it all out. I would start working on it in earnest in about a million years. If you wait a couple billion, more of the stuff in the universe might have decayed, and the end result might be less interesting, I guess.
Please tell whatever else is around about the rest of us!
When things are predictable they can be simulated fast : A spinning ball in the void can be simulated for 10^78 years in O(1).
When things are fuzzy, they can be simulated fast : A star made of huge number of atoms is not so different than another star made of a huge number of atoms. When processes are too complex they tend to all follow the law of large numbers which makes the computations memoizable.
What you want is a way to prevent the universe from taking shortcuts in its computations. Luckily its quite easy. You have to make details important. That's where chaos theory comes to the rescue. Small perturbations can have big impacts. Bifurcations like tossing a coin in the air create pockets of complexity. But throw too many coins in the air and its just random and boring. Life exists on this edge where enough structure is preserved to allow enough richness to exist.
One way humans have found of increasing precision is the lathe, which lead to building computers. Build a big enough fast enough computer and you will run-out of flops faster than reaching the 10^78 endgame.
But you have to be smart, because computation being universal it means that if you are just building a big computer what matters will be what runs on it. And your universe can be reduced to a recursive endgame state of "universe becoming a computer running universe simulation of a specific type", which doesn't need to computed more than once and already was, or isn't interesting enough to deserve being computed.
That's why we live on the exciting edge before the Armageddon, boring universes having already been simulated. The upside being universe hasn't yet decided which endgame we may reach, because the phytoplankton aliens of k2-18b have not yet turned on their supercomputer.
We are barely able to handle technological progress that would seem like stone age or even worse to a potential species that may exist at that time (ie those that may have such technology to stop the death of the very universe they are living)
They might just be indistinguishable from a god if there is one. And if they have enough power to perhaps prevent the death of the universe, they might have enough technology to just recreate another one. Or open a wormhole and transport to a new one or travel the multiverse or something.
Basically I feel if such kind of technology can be created to bend the universe to your will, it would be misused so badly, it might be catastrophic for the existence of such a species.
They say their findings set "a general upper limit for the lifetime of matter in the universe."
Perhaps we can set up a secret program where AI randomly selects individuals based on merit, character to get the latest in life extension treatments, philosophical and spiritual education so they can guide us (with AI assistence) into the future and beyond the solar system.
If we survive, 'we' most probably don't exist by that time in any recognisable shape or form.
The idealized Star Trek society of production automation and exploratory self fulfillment might only be possible, and sustainable, if we are a billion people.
That is still plenty enough people to continue our ever accelerating and vast exploration of culture, science and space.
If you were in a place where time was still you'd have no idea it were the case. Time would still tick at one second per second. You could only tell when you looked at some other object/patch of space that had a different ticking clock.
Well I can predict the next trend, launching very rich people's body into space so it will last 10^90 years :)
Over periods of time that long it's much more likely you'll run into some other object, say fall into a gravity well or something like that.
Even if you don't, pure erosion from neutral hydrogen and space dust will have disintegrated your capsule long before then.
If so, does this theoretically mean that a cyclic universe is possible in this way, and that if one were to go far enough - impossibly, unfathomably far - you might find the remnants of other universes?
To dispel a misconception: They're not some hypothetical type of brain that exists as pure quantum fluctuations (though those are even more likely). Boltzmann was talking about the probability of actual flesh-and-blood human brains arising spontaneously out of the vacuum.