Well at least the datetime library would be a perfectly reasonable place to handle leap seconds. The place that outputs the timestamp to a human readable format wouldn’t at all be that hard pressed to add a second when printing out the local time with timezone considered. It really wouldn’t add that much complexity.
Could you imagine if anyone was stupid enough to think the right place to handle such a thing was the internal counter of seconds rather than the datetime library though? Ha! That’d be ridiculous right! Imagine all the bugs if someone put something that’s only relevant to local timezone time printing there! It’d cause so many unexpected bugs!
Great wiki page!
It even mentions Boltzmann Brains!
“ This infinite future could allow for the occurrence of massively improbable events, such as the formation of Boltzmann brains.”
But taking this the other way around : it's also interesting that some cosmologies are known to be incorrect, because they would enable alternative forms of consciousness.
For dramatic effect, my monitor turned off right after "By this point, distant galaxies and starts are receding so fast that their light has become undetectable."
To survive beyond 1 Gy from now, life will need to move underground where the water is and hopefully much cooler than the eventual surface. Also, such life may/will become necessary to relocate to Mars, hopefully taking resources with them. (I don't say "us" because of likely dramatic evolution.)
The only reason that the subsurface rock is cooler than magma is being able to conduct heat through to a cooler surface. When that surface becomes exterminatingly hot and remains so for a while the subsurface will be heating up too. Since the sun is estimated to remain a red giant for about one Gy it will become hotter than the surface.
Completely in line with our propensity for destabilizing harmonic systems in nature. Imagine we do that and all of the other planetary orbits degenerate or become dangerous.
Considering 10^1100 years was the previously postulated time to decay then, assuming the Netherlands Research School for Astronomy is correct in their 10^78 years calculation, 10 years is still significantly closer to the correct date.
It could either be your fonts and/or your particular platform. I've seen this sort of thing before elsewhere, I think on Windows with certain fonts IIRC. I opened it on Firefox 138.0.1 on aarch64 for mac and there weren't any artifacts.
Upgrade to Universe 2.0 before our EOL date of 10⁷⁸ and receive a free 10⁸ month trial of Universe+ with cosmic karma monitoring and additional features such as dark mode.
I wish the universe would give me the option not to restart and apply this update right in the middle of a project! It's not like I was working on something or had my browser tabs the way that I like them.
> No. The CMBR of the current universe gives a nice comforting grey. Upgrade today for VantaBlack cosmos, guaranteed no EM at all!
Offer not available for Stuart Semple.
(Incidentally, if you don't know about this wonderful feud, it's worth reading up on it. If you know a little bit about it but have not kept up with the news, it may give a flavor of the whole to know that Stuart Semple's latest troll (that I am aware of) was changing his name to Anish Kapoor.)
I wonder how you decide to measure things in years on this scale. I mean, in about 10^10 years, the whole concept of a 'year' will stop to exist. What will you do then?
I would expect something like 'tera-seconds', or something related to a cosmological constant but at cosmological scale, like the time to decay hydrogen or number of caesium vibrations for example, but then scaled at AU scale. A value not related to time or space.
A year is defined in multiples of caesium vibrations. Not originally, obviously, but in this context it is. You cannot nearly measure any of these time periods precisely enough that any of this matters anyway.
My pet theory: all atoms decay back to hydrogen given enough time, gravity pulls them together, stars form, the universe is one big loop that self resets :)
I went to a talk of his on CCC ages ago, and it was such a fascinating combination of geometry, causality, and asymptotics. I have absolutely no clue whether it's reasonable physically, but independent of that, it's just a really elegant fusion of topics in a fun to think about way. Worth a read for anyone who just appreciates elegant new ways of combining mathematical structures.
I've also seen this talk, at the behest of some spaced out friends of mine, an amazing experience and I still think about the universe through the lens of that talk!
If everything is massless, everything travels at the speed of light, and nothing experiences any time (photons travel null geodesics with zero spacetime interval).
This is required to make Penrose's end state Conformal i.e. scale invariant, so that it can arbitrarily Cycle to a small scale to make a new Bing Bang Cosmology (CCC).
My understanding of this idea is that once the universe reaches a state of maximum entropy (this is the “heath death” of the universe, where everything is a uniform, undifferentiated cloud of photons, then time stops being meaningful because there can be no change from moment to moment. In a sense, time _is_ the change from low to high entropy - if you don’t have any entropy gradient, you can’t have any time either.
I've always rejected the idea that time is entropy change.
First, in many local processes entropy moves from high to low (e.g. life). Nobody says that time is moving backwards for living things. It only increases if you consider the system it is embedded in as well. So this idea that entropy is time is something that only applies to the entire universe?
It's true that we don't see eggs unbreaking, or broken coffee cups flying off the floor and reassembling. This increase in entropy seems to give an "arrow" of time, but to my mind this view (ironically) confuses cause with effect.
If you have any causal system (cause preceding effects) then you will always see this type of entropic increase, by simple statistics. There are just many, many more ways for things to be scrambled and high entropy than ordered and low entropy.
So yes, entropy does tend to increase over time, but that's an effect of being in a causal system, not the system itself. At least, that's my view.
Could you expand on your comment that life has entropy moving from high to low? Doesn't aging increase the entropy in our biological system? I have always thought that we are at our most structured in the early phases of conception with entropy increasing constantly as we age.
I took it as capital-L Life is moving from high to low. As evolution continues Life seems to evolve ever higher -> lower/more-ordered organisms (as more complex organisms depend on the systems created by simpler organisms prior to themselves).
I am slightly blending the concept of entropy and complexity. But "ordered complexity" is how I imagine it.
Life is essentially a process of creating order (lower entropy) building complex cells and so on using energy and matter from its environment.
Perfectly true that entropy gets us in the end as we age, as the system breaks down and cannot sustain itself any longer. Although if we could fix those systems, there's no reason in principle we couldn't halt aging entirely.
I don’t think entropy ever moves from high to low overall, it only ever distills some local low out of an higher entropy area, and in doing so, the overall entropy increases.
It works a bit like air conditioning: yeah, you can make one room cold, but only by making more heat outside the room. The overall temperature of the system increases.
This sounds sort of like the "if a tree falls in a forest and no one hears it, did it make a sound".
if time passes and there's no observable difference, did it pass? I guess it makes no meaningful difference, but it's not really answering the underlying question of if some variable is advancing or not.
I remember the book "Now - Physics of Time" by Richard Muller (a Berkley physics professor) touching on the subject of entropy linked to time, but I never got to finish the book and sadly I can't provide more insight.
And potentially leads to things like Boltzmann Brains, given enough time! Quantum fluctuations can still create wildly improbable things, even if only briefly.
Neutron decay is one of those things that I forgot between college physics classes and today and it was sort of surprising to rediscover it.
We also know that electrons eventually decay but it's something like 10^26 years, which is long enough to say that probably not many electrons in the solar system have decayed since the universe was born but the universe is really stupidly big, so it absolute numbers that could still be a lot of dead electrons. Maybe a solar system's worth.
Surprisingly there is no wikipedia page for this. Just rando articles.
Electrons do not decay, because there is nothing they could decay into. You need a lighter particle of the same charge due to charge conservation, and there is none.
Well... black holes don't evaporate into hydrogen, but into light and various light particles. The hydrogen left over at the heat death will necessarily be too diffuse due to the expansion of the universe. It can't light up again like that. Perhaps the computer in The Last Question was hallucinating at the end.
A) We don’t know if all derivatives are >= 0. e.g. if the jerk rate is < 0, then you’d expect contraction eventually. Similarly, if the derivative of the jerk rate is < 0 & so on. So even accelerating expansion could eventually lead to contraction.
B) We don’t have a lot of very highly compelling evidence that the universe is actually accelerating (at least nowhere like we do for the Big Bang). For example, alternate models have proposed that our apparent perception of the expansion is simply as a result of the effect of non-uniform gravity throughout the universe & that the vaccuum of space between galaxies has even less time dilation and that’s what make it look like things are expanding.
In other words, I’d put the model of a permanently expanding universe as less likely to actually match reality.
Maybe we should siphon off hydrogen and helium from the Sun for storage elsewhere in the Solar System to reduce the burn rate to prolong the usable lifetime of its fuel? And build a Dyson sphere. ;D
You've been watching too many bleak, post-apocalyptic, fatalist celebrations of losers. I'm talking about adding millions to billions of years of extra good life in the giant dome with plenty of temperature difference to keep entropy down for longer.
The Big Bang happened at the "north pole" of spacetime. Eventually all matter and energy will reach the "south pole" and recombine. The Big Crunch theory will never die!
The big bang happened at the center of the universe and every point of space is the center of the universe at all times. You could argue that the center of spacetime is definitionally the Big Bang since that’s when time is believed to have started to exist in the first place but we don’t have a good grasp of how to define the center of a 4D physical structure where one dimension is time which doesn’t seem to really act like the other dimensions.
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.
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.
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?
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.
> In 1975, physicist Stephen Hawking postulated that contrary to the theory of relativity, particles and radiation could escape from a black hole. At the edge of a black hole, two temporary particles can form, and before they merge, one particle is sucked into the black hole and the other particle escapes.
Hasn't this explanation been discredited for a while?
> Black holes are not decaying because there’s an infalling virtual particle carrying negative energy; that’s another fantasy devised by Hawking to “save” his insufficient analogy. Instead, black holes are decaying, and losing mass over time, because the energy emitted by this Hawking radiation is slowly reducing the curvature of space in that region. Once enough time passes, and that duration ranges from approximately 10^68 to 10^103 years for black holes of realistic masses, these black holes will have evaporated entirely.
Both explanations are merely simplifications of a truly complex phenomenon, so both are valid. Reducing space-time curvature is equivalent to the absorption of a virtual particle with negative energy
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?
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
The authors of the comment show that the "gravitational pair-production" rate used in the work in OP comes from truncating the covariant heat-kernel (proper-time) expansion of the one-loop effective action at second order in curvature, an approximation that is valid only in weak-field regions where all curvature invariants satisfy |R| · ℓ² ≪ 1 (where ℓ is the Compton wavelength). When that same expression is pushed into the high-curvature interior of a neutron star -- where the inequalities fail by many orders of magnitude -- the series is no longer asymptotic and its early terms generate a spurious imaginary part. Because the paper's entire mass-loss mechanism and lifetime bound follow from that uncontrolled imaginary term, its conclusions collapse.
Simply put, it doesn't even correspond to known experiments. It's entirely driven by a narrow artefact and has no physical basis.
There's a lot wrong with that reply -- it mostly just shifts the goalposts without answering the central objections raised in the comment.
Much of the reply revolves around whether the mixed invariant G=E⋅B appears at leading or higher order in the QED Schwinger result. But the comment's critique used the constant-field Schwinger problem only as a check that the authors' master formula fails against a case with an exact answer; the real complaint is that the same failure occurs for curved-spacetime examples where the exact result is known to vanish. Debating G is fine, but you can't ignore the gravitational case either.
The reply repeatedly says the comment is "outside the realm of applicability" of the formula -- as though that were the comment's fault! But if the formula cannot survive the very checks the authors themselves hold up (Schwinger with B≠0, Ricci-flat space), the burden is on the authors to (severely) restrict their own claims, not on critics to ignore the failure modes.
Naively speaking, these predictions seem like they should be very sensitive to all sorts of effects, some better understood than others. It's odd how many commenters here treat headlines like these as settled fact, instead of one team's calculations based on assumptions that may be wildly off.
I always assumed that an event horizon was a necessary condition for hawking radiation (or the Unruh effect, for inertial frames). Interesting that this apparently isn't the case, and the authors rather predict all objects with mass to have this property.
That is about within a factor of 1000 of the number of atoms in the universe. So divide the universe into 1000 compartments of equal atom count, and there is about 1 year left for each atom in there.
To put this in perspective, a drop of water is about 1 trillion groups of 100 billion atoms (or 100 sextillion atoms).
> That is about within a factor of 1000 of the number of atoms in the universe. So divide the universe into 1000 compartments of equal atom count, and there is about 1 year left for each atom in there.
This sounds tedious, but it might help to realize you can just gather all the atoms together first, and then count only every 1000th one.
Evaporation isn’t as bad as false vacuum decay. I thought the news would be about that. Fast vacuum decay would be much worse, as civilization can withstand matter loss but not the ultimate false vacuum decay
Who knows? Maybe when and if that happens, civilizations will be advanced enough to try to reverse this: manipulating the local Higgs field, pocket universes, and counter-decay waves
The problem is that false vacuum decay spreads at the speed of light, leaving no time for preparation, and the laws of physics would be completely altered without warning. Perhaps future civilizations could resist it, but with our current understanding, it’s a doomsday in a blink of an eye
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.
TLDR: Hawking radiation can cause things besides black holes to evaporate.
Man and moon: 10^90 years
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. Of course, the researchers subtly note, there are other processes that may cause humans and the moon to disappear faster than calculated.
It would be the great-great-great-... Actually, there aren't enough electrons in this system to encode all the great-s needed to express the name of the generation.
I'm all for thinking of the children, but planning at that range is probably impossible.
When we’re dead, I know we don’t feel anything, but when the universe also becomes dead I wonder if we’ll not feel anything to a degree that we didn’t even know possible, a death beyond death, if that makes sense. It’s like not only are we dead and gone, but our entire life is gone so thoroughly that it’s like it never even happened, and if it never even happened, what the hell is this moment we experience now? Just a passing illusion as a universe explodes?
I was thinking that since apparently Hawking radiation applies to all objects (I thought it was just black holes), maybe it would be interesting to try to actually observe it on the moon. But then I ran the numbers and, if the authors are correct, the moon is losing about 1 electron mass to Hawking radiation every 10^37 years!
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.
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 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!
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.
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.
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.
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.
>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 :)
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.
Aw fuck, I was looking forward to curing a few more deaths and bringin the Bitchun Society to yet more barbarian tribes in the outer reaches. I wonder if my whuffie will last that long? I really don't want to deadhead so hopefully there's plenty more interesting things to do in the tail end.
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.
I am suspicious this attitude is responsible for much personal and environmental destruction. I wonder how we can remove it from humanity; it is one of the most dangerous pervasive mindsets for our, and the biosphere's survival.
One of my favorite Wikipedia pages
https://en.wikipedia.org/wiki/Timeline_of_the_far_future
> in 10k years (…) the average length of a solar day will be 1⁄30 of an SI second longer than it is today.
Looks like a new test case scenario for libraries that handle time/date.
Well at least the datetime library would be a perfectly reasonable place to handle leap seconds. The place that outputs the timestamp to a human readable format wouldn’t at all be that hard pressed to add a second when printing out the local time with timezone considered. It really wouldn’t add that much complexity.
Could you imagine if anyone was stupid enough to think the right place to handle such a thing was the internal counter of seconds rather than the datetime library though? Ha! That’d be ridiculous right! Imagine all the bugs if someone put something that’s only relevant to local timezone time printing there! It’d cause so many unexpected bugs!
Am I misreading something, or isn't that already in 1,000 years?
You are correct, I made a typo in the grandparent comment - it should have been 1k years. Unfortunately I can no longer edit.
At 10^78 years we could use 512 bit time stamps and be safe from overflow and measure all the way down to Planck time.
Insertion of a leap second every month.
Great wiki page! It even mentions Boltzmann Brains! “ This infinite future could allow for the occurrence of massively improbable events, such as the formation of Boltzmann brains.”
Boltzmann Brains usually mean something is wrong in your cosmology
But taking this the other way around : it's also interesting that some cosmologies are known to be incorrect, because they would enable alternative forms of consciousness.
Or with our philosophy around anthropic reasoning. Or both.
In video form: https://www.youtube.com/watch?v=uD4izuDMUQA
For dramatic effect, my monitor turned off right after "By this point, distant galaxies and starts are receding so fast that their light has become undetectable."
There's also this lovely musical video https://www.youtube.com/watch?v=FMJNta-okRw
The "no more strength, no way out" part kills me every time I watch it.
My favourite sleep aid video.
I feel like you could build an entire meditation practice around reading this article.
That or existential dread.
Here's my favorite youtube version of this:
https://youtu.be/uD4izuDMUQA
It pairs well with https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe
To survive beyond 1 Gy from now, life will need to move underground where the water is and hopefully much cooler than the eventual surface. Also, such life may/will become necessary to relocate to Mars, hopefully taking resources with them. (I don't say "us" because of likely dramatic evolution.)
The only reason that the subsurface rock is cooler than magma is being able to conduct heat through to a cooler surface. When that surface becomes exterminatingly hot and remains so for a while the subsurface will be heating up too. Since the sun is estimated to remain a red giant for about one Gy it will become hotter than the surface.
At that scale of time, it's not implausible that we have the technology to relocate Earth itself by then (e.g. increase its orbit).
Completely in line with our propensity for destabilizing harmonic systems in nature. Imagine we do that and all of the other planetary orbits degenerate or become dangerous.
1 Gy ago, life wasn’t multicellular.
I don’t think we have the ability to meaningfully predict such scales.
If Reid Malenfant or Jim Bolder aren't involved, this isn't the deep time future I'm interested in.
So given these finding, that page will need to be overhauled a lot
My HN reader displays this topic as "Universe expected to decay in 10 years, much sooner than previously thought".
And it's not wrong, that _is_ much sooner than previously thought!
Considering 10^1100 years was the previously postulated time to decay then, assuming the Netherlands Research School for Astronomy is correct in their 10^78 years calculation, 10 years is still significantly closer to the correct date.
If these trends continue.... Ayyyy
We are doooooomed!
Looking forward to Universe II Electric Boogaloo
What’s it called when the exponent is off by an order of magnitude, ha..
OOM off by one OOM is 10^10, so its a factor of 10 billion.
Good time to take out a 30-year mortgage.
> My HN reader [...]
What reader do you use? I've only ever used vanilla HN.
Hews 2 on Android. I have a Pixel 6. Generally I'm satisfied with Hews 2, it just rendered this particular title in a funny way.
I use harmonic
Interesting, I'm on harmonic too but the text is fine.
Sorry for the duplicate comment. Seems harmonic doesn't like when you have poor cell connection.
Interesting, I'm in harmonic too but the text is fine.
Firefox displays 10^78 with boxes for superscript. Chrome doesn't have any problem.
It could either be your fonts and/or your particular platform. I've seen this sort of thing before elsewhere, I think on Windows with certain fonts IIRC. I opened it on Firefox 138.0.1 on aarch64 for mac and there weren't any artifacts.
Windows has limited font substitution support, that's probably why.
I'm on Firefox -- no problems. Both on Android and Linux.
Firefox on Android mobile displays it fine. Probably an OS level font issue.
Displayed just fine in Brave as well, for the curious.
I mean, it's already decaying. So it will be decaying in 10 years too.
It's really a question of when it will stop decaying.
It used to be decaying. It's still decaying, but it used to, too.
The Universe asked me, "Guess what? I'm decaying"
I said, "Dude, you've gotta give me time to guess"
If there is nobody left to observe when it stops decaying, will it ever stop decaying?
Complete/Finish might be clearer.
There go my vacations! :)
Upgrade to Universe 2.0 before our EOL date of 10⁷⁸ and receive a free 10⁸ month trial of Universe+ with cosmic karma monitoring and additional features such as dark mode.
I wish the universe would give me the option not to restart and apply this update right in the middle of a project! It's not like I was working on something or had my browser tabs the way that I like them.
I... I thought we already had dark mode..
No. The CMBR of the current universe gives a nice comforting grey. Upgrade today for VantaBlack cosmos, guaranteed no EM at all!
Thermodynamic purists hate this thing!
ugh, no zero-point energy? What a regression.
> No. The CMBR of the current universe gives a nice comforting grey. Upgrade today for VantaBlack cosmos, guaranteed no EM at all!
Offer not available for Stuart Semple.
(Incidentally, if you don't know about this wonderful feud, it's worth reading up on it. If you know a little bit about it but have not kept up with the news, it may give a flavor of the whole to know that Stuart Semple's latest troll (that I am aware of) was changing his name to Anish Kapoor.)
cranks up music to 999999 dB
I wonder how you decide to measure things in years on this scale. I mean, in about 10^10 years, the whole concept of a 'year' will stop to exist. What will you do then?
I would expect something like 'tera-seconds', or something related to a cosmological constant but at cosmological scale, like the time to decay hydrogen or number of caesium vibrations for example, but then scaled at AU scale. A value not related to time or space.
A year is defined in multiples of caesium vibrations. Not originally, obviously, but in this context it is. You cannot nearly measure any of these time periods precisely enough that any of this matters anyway.
My pet theory: all atoms decay back to hydrogen given enough time, gravity pulls them together, stars form, the universe is one big loop that self resets :)
You're in good company. Something similar, minus the hydrogen phase, is proposed by Roger Penrose: https://en.wikipedia.org/wiki/Cycles_of_Time
I went to a talk of his on CCC ages ago, and it was such a fascinating combination of geometry, causality, and asymptotics. I have absolutely no clue whether it's reasonable physically, but independent of that, it's just a really elegant fusion of topics in a fun to think about way. Worth a read for anyone who just appreciates elegant new ways of combining mathematical structures.
I've also seen this talk, at the behest of some spaced out friends of mine, an amazing experience and I still think about the universe through the lens of that talk!
Apparently time ceases when absolutely all mass is gone, because mass is required for a clock.
This of course requires the decay of protons.
Why would time cease because all the measuring devices were gone?
If everything is massless, everything travels at the speed of light, and nothing experiences any time (photons travel null geodesics with zero spacetime interval).
This is required to make Penrose's end state Conformal i.e. scale invariant, so that it can arbitrarily Cycle to a small scale to make a new Bing Bang Cosmology (CCC).
Yes, that's a good point. But does that mean that the quantum field fluctuations in the space time the massless radiation moves through also ceases?
My understanding of this idea is that once the universe reaches a state of maximum entropy (this is the “heath death” of the universe, where everything is a uniform, undifferentiated cloud of photons, then time stops being meaningful because there can be no change from moment to moment. In a sense, time _is_ the change from low to high entropy - if you don’t have any entropy gradient, you can’t have any time either.
I've always rejected the idea that time is entropy change.
First, in many local processes entropy moves from high to low (e.g. life). Nobody says that time is moving backwards for living things. It only increases if you consider the system it is embedded in as well. So this idea that entropy is time is something that only applies to the entire universe?
It's true that we don't see eggs unbreaking, or broken coffee cups flying off the floor and reassembling. This increase in entropy seems to give an "arrow" of time, but to my mind this view (ironically) confuses cause with effect.
If you have any causal system (cause preceding effects) then you will always see this type of entropic increase, by simple statistics. There are just many, many more ways for things to be scrambled and high entropy than ordered and low entropy.
So yes, entropy does tend to increase over time, but that's an effect of being in a causal system, not the system itself. At least, that's my view.
Could you expand on your comment that life has entropy moving from high to low? Doesn't aging increase the entropy in our biological system? I have always thought that we are at our most structured in the early phases of conception with entropy increasing constantly as we age.
I took it as capital-L Life is moving from high to low. As evolution continues Life seems to evolve ever higher -> lower/more-ordered organisms (as more complex organisms depend on the systems created by simpler organisms prior to themselves).
I am slightly blending the concept of entropy and complexity. But "ordered complexity" is how I imagine it.
Life is essentially a process of creating order (lower entropy) building complex cells and so on using energy and matter from its environment.
Perfectly true that entropy gets us in the end as we age, as the system breaks down and cannot sustain itself any longer. Although if we could fix those systems, there's no reason in principle we couldn't halt aging entirely.
I don’t think entropy ever moves from high to low overall, it only ever distills some local low out of an higher entropy area, and in doing so, the overall entropy increases.
It works a bit like air conditioning: yeah, you can make one room cold, but only by making more heat outside the room. The overall temperature of the system increases.
This sounds sort of like the "if a tree falls in a forest and no one hears it, did it make a sound".
if time passes and there's no observable difference, did it pass? I guess it makes no meaningful difference, but it's not really answering the underlying question of if some variable is advancing or not.
I remember the book "Now - Physics of Time" by Richard Muller (a Berkley physics professor) touching on the subject of entropy linked to time, but I never got to finish the book and sadly I can't provide more insight.
stuff can still happen after the heat death. the universe will keep expanding, and quantum foam will keep foaming.
heat death just implies no work can be done. time still flows
And potentially leads to things like Boltzmann Brains, given enough time! Quantum fluctuations can still create wildly improbable things, even if only briefly.
>Why would time cease because all the measuring devices were gone?
Partly, but mostly because there would be no lunch, so there would be no illusion of lunch-time any more.
This is clearly the correct answer :)
The proton itself that forms the hydrogen atom might decay (we don't know yet; we do know that neutrons decay after 15 minutes).
https://en.wikipedia.org/wiki/Proton_decay
Neutron decay is one of those things that I forgot between college physics classes and today and it was sort of surprising to rediscover it.
We also know that electrons eventually decay but it's something like 10^26 years, which is long enough to say that probably not many electrons in the solar system have decayed since the universe was born but the universe is really stupidly big, so it absolute numbers that could still be a lot of dead electrons. Maybe a solar system's worth.
Surprisingly there is no wikipedia page for this. Just rando articles.
Electrons do not decay, because there is nothing they could decay into. You need a lighter particle of the same charge due to charge conservation, and there is none.
You might be thinking of protons.
Well... black holes don't evaporate into hydrogen, but into light and various light particles. The hydrogen left over at the heat death will necessarily be too diffuse due to the expansion of the universe. It can't light up again like that. Perhaps the computer in The Last Question was hallucinating at the end.
The evidence about the accelerating expansion of the universe would seem to contradict that theory.
Not necessarily.
A) We don’t know if all derivatives are >= 0. e.g. if the jerk rate is < 0, then you’d expect contraction eventually. Similarly, if the derivative of the jerk rate is < 0 & so on. So even accelerating expansion could eventually lead to contraction.
B) We don’t have a lot of very highly compelling evidence that the universe is actually accelerating (at least nowhere like we do for the Big Bang). For example, alternate models have proposed that our apparent perception of the expansion is simply as a result of the effect of non-uniform gravity throughout the universe & that the vaccuum of space between galaxies has even less time dilation and that’s what make it look like things are expanding.
In other words, I’d put the model of a permanently expanding universe as less likely to actually match reality.
Iron is the most stable atomic nucleus (at least if we don’t consider Nickel-62).
But will the sequence of events be exactly the same in each loop iteration?
Heat death is just so depressing.
Maybe we should siphon off hydrogen and helium from the Sun for storage elsewhere in the Solar System to reduce the burn rate to prolong the usable lifetime of its fuel? And build a Dyson sphere. ;D
I've watched enough Doctor Who to know that being the last one alive at the end of time is pretty goddamned lonely. And dark.
You can have all of my poptarts, I'm likely to check out.
You've been watching too many bleak, post-apocalyptic, fatalist celebrations of losers. I'm talking about adding millions to billions of years of extra good life in the giant dome with plenty of temperature difference to keep entropy down for longer.
This won't stop the heat death of the universe, just prolong the life of one particular solar system a bit.
My pet theory:
The Big Bang happened at the "north pole" of spacetime. Eventually all matter and energy will reach the "south pole" and recombine. The Big Crunch theory will never die!
The big bang happened at the center of the universe and every point of space is the center of the universe at all times. You could argue that the center of spacetime is definitionally the Big Bang since that’s when time is believed to have started to exist in the first place but we don’t have a good grasp of how to define the center of a 4D physical structure where one dimension is time which doesn’t seem to really act like the other dimensions.
Are you saying you're the center of the universe?
Better get around to painting those Warhammer minis soon
I gotta start working on my reading backlog. Luckily I already returned all my library books.
It is written
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.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.
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.
> Pairs of particles appear spontaneously. One falls into the gravitational field, losing energy.
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
Hawking never knew "what really is going on". He wrote some nice hypotheses, but he never knew for sure, and was not ever close to knowing.
But he did know the simplification was wrong.
>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?
No, all objects with non-zero temperature radiate heat. Stars, white dwarfs, black holes, even the universe itself.
I said
so radiated and absorbed heat should already be accounted for, right?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.
> In 1975, physicist Stephen Hawking postulated that contrary to the theory of relativity, particles and radiation could escape from a black hole. At the edge of a black hole, two temporary particles can form, and before they merge, one particle is sucked into the black hole and the other particle escapes.
Hasn't this explanation been discredited for a while?
https://bigthink.com/starts-with-a-bang/hawking-radiation-bl...
> Black holes are not decaying because there’s an infalling virtual particle carrying negative energy; that’s another fantasy devised by Hawking to “save” his insufficient analogy. Instead, black holes are decaying, and losing mass over time, because the energy emitted by this Hawking radiation is slowly reducing the curvature of space in that region. Once enough time passes, and that duration ranges from approximately 10^68 to 10^103 years for black holes of realistic masses, these black holes will have evaporated entirely.
https://bigthink.com/starts-with-a-bang/hawking-radiation-re...
Both explanations are merely simplifications of a truly complex phenomenon, so both are valid. Reducing space-time curvature is equivalent to the absorption of a virtual particle with negative energy
There’s no way that we happen to exist in just the first 10^78 years of eternity.
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?
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.
If the big bang created space and time, "before the big bang" is not really well-defined.
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.
From inside that universe there still was no "before". Are you looking into our universe from the outside? ;)
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.
[1]: https://astronomy.stackexchange.com/questions/49248/interpre...
[2]: https://en.wikipedia.org/wiki/Timeline_of_the_far_future
> Can you provide the source for that quote? 5 billion years seems way too soon.
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...
Is that right? Only 5 billion years until noone sees the background radiation and other galaxies?!
That's... awe inspiring.
That seems relatively soon! I know it's a huge number, but on universal scales, that's crazy
Which leads one to wonder what phenomena we were too late to observe and which of our assumptions are therefore faulty
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.
This is a good reason not to throw away your old textbooks.
Very strongly suggest you check out Isaac Asimov’s “The Last Question”
https://users.ece.cmu.edu/~gamvrosi/thelastq.html
Or, for an alternative and rather more in depth treatment, Stephen Baxter's "Manifold: Time"
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!
PBS Space Time vibes
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.
This is a wacky, seemingly out-of-place philosophical comment, yet I have had similar thoughts, so I give you an irreverent upvote.
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.
The origami of petal unfolding implies the rose blooms forever says all bugkind dwelling on the bud.
We can’t know yet.
See The Last Question, by Isaac Asimov:
https://users.ece.cmu.edu/~gamvrosi/thelastq.html
It's interesting to note, that the Universal AC in “The Last Question” did not hallucinate an answer.
Instead, its response—"INSUFFICIENT DATA FOR MEANINGFUL ANSWER"—is a model of intellectual honesty.
Why, so we can extend the 10^78 years? I'm not sure you truly understand how large 10^78 years is, or even 10^10 years.
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.
Humanity has existed for 3x10^6 years (give or take), which is 1 x 10^-72 of that time period.
We don't need to worry, it is highly unlikely that humanity as we recognize it will exist.
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.
it won't be humanity, but it should hopefully be some sort of intelligence
Imagine if we solve it. Then hope to preserve the answer long enough, that people will care.
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?!
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.
Presumably civilization will be using iron stars by then?
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?
They'll exist because of Wan-To.
The World at the End of Time by Frederick Pohl.
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
The only serious answer is that we have absolutely no way of knowing that.
There's a very entertaining Dwarkesh podcast with Adam Brown about this: https://www.dwarkesh.com/p/adam-brown
Humans are the universe contemplating this.
The Second Law of Thermodynamics is an immutable characteristic of our universe. Entropy in a closed system (like the universe) is irreversible.
It was set to zero once, so somebody somewhere/somewhen figured it out before.
Or rather we are a fork/thread somewhere is spacetime.
git branch
lolwut?
Bad news for Boltzmann brains
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.
They may not actually happen: https://arxiv.org/abs/1505.02780
Why they should be limited to our universe?
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.
Yep the difference between 10^78 and 10^1100 is approximately 10^1100…
get your affairs in order.
Another 10^3 would be good for humanity
Bad news for my proton decay stocks
Somewhere out there, a physicist probably got tenure writing the paper. Meanwhile, I’m just trying to keep my inbox from decaying in 10^3 seconds.
It's nonsense.
See this comment on their previous paper: https://arxiv.org/abs/2306.07628
The authors of the comment show that the "gravitational pair-production" rate used in the work in OP comes from truncating the covariant heat-kernel (proper-time) expansion of the one-loop effective action at second order in curvature, an approximation that is valid only in weak-field regions where all curvature invariants satisfy |R| · ℓ² ≪ 1 (where ℓ is the Compton wavelength). When that same expression is pushed into the high-curvature interior of a neutron star -- where the inequalities fail by many orders of magnitude -- the series is no longer asymptotic and its early terms generate a spurious imaginary part. Because the paper's entire mass-loss mechanism and lifetime bound follow from that uncontrolled imaginary term, its conclusions collapse.
Simply put, it doesn't even correspond to known experiments. It's entirely driven by a narrow artefact and has no physical basis.
The authors wrote a reply to that comment
https://arxiv.org/pdf/2308.12326
I think about how some relativists think you could see a Hawking Radiation like effect if you're accelerating
https://en.wikipedia.org/wiki/Unruh_effect
although the idealized case of endless acceleration implies a certain kind of horizon
https://en.wikipedia.org/wiki/Rindler_coordinates
maybe the horizon doesn't matter much,.
There's a lot wrong with that reply -- it mostly just shifts the goalposts without answering the central objections raised in the comment.
Much of the reply revolves around whether the mixed invariant G=E⋅B appears at leading or higher order in the QED Schwinger result. But the comment's critique used the constant-field Schwinger problem only as a check that the authors' master formula fails against a case with an exact answer; the real complaint is that the same failure occurs for curved-spacetime examples where the exact result is known to vanish. Debating G is fine, but you can't ignore the gravitational case either.
The reply repeatedly says the comment is "outside the realm of applicability" of the formula -- as though that were the comment's fault! But if the formula cannot survive the very checks the authors themselves hold up (Schwinger with B≠0, Ricci-flat space), the burden is on the authors to (severely) restrict their own claims, not on critics to ignore the failure modes.
Very strange prediction indeed, the object need an event horizon for hawking radiation to occur
Naively speaking, these predictions seem like they should be very sensitive to all sorts of effects, some better understood than others. It's odd how many commenters here treat headlines like these as settled fact, instead of one team's calculations based on assumptions that may be wildly off.
Despite it being quite a way out it's still a little sad to think the end is coming.
"quite a way out"... is doing a lot of work in that sentence.
I always assumed that an event horizon was a necessary condition for hawking radiation (or the Unruh effect, for inertial frames). Interesting that this apparently isn't the case, and the authors rather predict all objects with mass to have this property.
That is about within a factor of 1000 of the number of atoms in the universe. So divide the universe into 1000 compartments of equal atom count, and there is about 1 year left for each atom in there.
To put this in perspective, a drop of water is about 1 trillion groups of 100 billion atoms (or 100 sextillion atoms).
So, we got some time left.
> That is about within a factor of 1000 of the number of atoms in the universe. So divide the universe into 1000 compartments of equal atom count, and there is about 1 year left for each atom in there.
This sounds tedious, but it might help to realize you can just gather all the atoms together first, and then count only every 1000th one.
According to The End of Everything (https://www.goodreads.com/book/show/52767659-the-end-of-ever...) decay is only one of the ways it all ends. Unfortunately most (all?) the other ways happen way earlier.
Evaporation isn’t as bad as false vacuum decay. I thought the news would be about that. Fast vacuum decay would be much worse, as civilization can withstand matter loss but not the ultimate false vacuum decay
>ultimate
Who knows? Maybe when and if that happens, civilizations will be advanced enough to try to reverse this: manipulating the local Higgs field, pocket universes, and counter-decay waves
The problem is that false vacuum decay spreads at the speed of light, leaving no time for preparation, and the laws of physics would be completely altered without warning. Perhaps future civilizations could resist it, but with our current understanding, it’s a doomsday in a blink of an eye
good news, we'll never need more than a 512 bit time_t
Other gravitational bodies radiating via hawking radiation is a bold claim. Has this work been validated? Challenged? Confirmed?
Accepting table reservations now, you won’t want to miss this.
Sorry I'm busy that day. Can we schedule for the following... oh. How about the previous Tuesday?
It's the first time I see unicode exponent numbers actually get used
People will be gathering at the Restaurant At The End Of the Universe with Douglas Adams as the host.
Now I feel like an idiot for paying off my house
"Estimate of the remaining time before universe decays expected to be revised 10^76 times before its finally over"
(conservatively assuming the estimate will be revised about once every hundred years as we learn more).
Darn, I'll have to cancel my party plans for that weekend.
Damn. That ruins my retirement plans
just in time for your 401k to recover :)
If anyone here happens to be immortal, how will you plan around this?
> Previous studies, which did not take this effect into account, put the lifetime of white dwarfs at 10^1100 years
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
Damn, I had planned to go shopping on that day!
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?
Isn't time relative?
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.
Bad news for Bryan Johnson, he will have to adjust some of his long term plans
This is the original paper: https://arxiv.org/abs/2410.14734
They say their findings set "a general upper limit for the lifetime of matter in the universe."
TLDR: Hawking radiation can cause things besides black holes to evaporate.
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. Of course, the researchers subtly note, there are other processes that may cause humans and the moon to disappear faster than calculated.That's really bad news for immortals.
Better make friends with the creation immortals so you get invited to their parties.
Relative to that time scale we are still, at ~10¹⁰ years, in the opening moments of the universe.
If an age of the universe passed for every year the universe has already existed, we'd still have some time left at the end.
If humans end up existing at 10^77 years. You would hope and imagine that they would be prepared for the decay?
Well, that's only 10% of the way there, so they'd still have most of the time left.
Let the grandkids worry about it. Now would you be a pal and hand me another another atomic mimosa?
It would be the great-great-great-... Actually, there aren't enough electrons in this system to encode all the great-s needed to express the name of the generation.
I'm all for thinking of the children, but planning at that range is probably impossible.
with what's going on, not sure if human will exist in the next 10 years
This is as removed from any observation and predictive utility as counting angels on the head of a pin.
Damn... got to adjust the roadmap. Universe heat death milestone just got moved up.
Could be just one accidental Ctrl+C away.
One more argument not to do anything about climate change. After all universe is going decay shortly...
I hope they’re working on finding a way to massively decrease the net entropy in the universe after this.
Unfortunately there is as yet insufficient data for a meaningful answer
Crack on with it and don't keep us in the dark!
The way to do that is to do the most unlikely things
In the long run we're all dead aren't we?
You were dead before. On average you’ve been dead the whole time.
And taxes
I believe most jurisdictions stop taxing you when you're dead.
Glad to see my Collapsing Universe Theory is starting to happen
Oh no, all my plans for the 10^100 year celebration party!
When we’re dead, I know we don’t feel anything, but when the universe also becomes dead I wonder if we’ll not feel anything to a degree that we didn’t even know possible, a death beyond death, if that makes sense. It’s like not only are we dead and gone, but our entire life is gone so thoroughly that it’s like it never even happened, and if it never even happened, what the hell is this moment we experience now? Just a passing illusion as a universe explodes?
Oh no! What are we going to do about this?
OMG, the economy
Did Broadcom acquire this Universe?
Probably on a Thursday. I never could get the hang of Thursdays.
i'll have to move that meeting forward.
I was thinking that since apparently Hawking radiation applies to all objects (I thought it was just black holes), maybe it would be interesting to try to actually observe it on the moon. But then I ran the numbers and, if the authors are correct, the moon is losing about 1 electron mass to Hawking radiation every 10^37 years!
so many years - and how many miles?
/remindme in 10^60 years
so i wonder what comes after?
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.
There is a theory out there that once heat death is done distance is meaningless, therefore zero, therefore big bang again.
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 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.
Conformal cyclic cosmology, by Roger Penrose
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 would be a weird thing for nothingness to change state.
If there are no physical laws, there’s nothing to stop that happening.
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.
https://youtu.be/mht-1c4wc0Q
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 Credits
How can the universe come from an infinite point and have no Centre.
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.
The center is everywhere.
Good. Maybe now they can prove Hawking radiation in something that isn't a bath tub. Or an oven.
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.
You'd like this book: https://mitpress.mit.edu/9780262547222/an-infinity-of-worlds...
There's a teapot orbiting the sun between Earth and Mars too.
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.
To me that still sounds like forever.
Ah, just time for another bath. Pass me the sponge somebody, will you?
>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 :)
Depends what you mean by last.
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.
the term "sooner" in this case is, you know, relative
Time to dig into that game backlog on Steam.
AI is going to take over anyways
It'll be 42'd like everything else
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.
What values do you think we should optimize for?
I suspect we have more immediate problems than "can we survive the next n billion years".
There have already been close calls with nukes. No way in hell we last another hundred.
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.
Aw fuck, I was looking forward to curing a few more deaths and bringin the Bitchun Society to yet more barbarian tribes in the outer reaches. I wonder if my whuffie will last that long? I really don't want to deadhead so hopefully there's plenty more interesting things to do in the tail end.
> whuffie
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.
https://en.wikipedia.org/wiki/Down_and_Out_in_the_Magic_King...
So... Who cares. No one is going to be around even 10^3 years from now. It doesn't help anyone to know, and there's nothing we can do about it.
I am suspicious this attitude is responsible for much personal and environmental destruction. I wonder how we can remove it from humanity; it is one of the most dangerous pervasive mindsets for our, and the biosphere's survival.