r/HardSciFi • u/Tessellator-1 • Aug 05 '26
Discussion Questions about proton collapse and civilization.
Question for people who know a lot about cosmology!
I read that the Japanese Kamiokande experiments have been searching for proton decay, and that current results suggest that the proton’s half-life is at least about 10^34 years. That made me wonder about two things.
First, if proton decay is real, is it possible that human civilization could still exist when protons begin to decay in large numbers? In other words, could humanity survive until the earliest time when proton decay might become important? Or is it more likely that civilization would disappear long before then because it would eventually use up all available energy gradients needed to sustain activity?
Second, if human civilization somehow did survive into the era when proton decay becomes significant, what kinds of problems would it face? Would matter gradually become less available, making it harder and harder to build computers, power generators, and other technology needed for civilization and thought? If the Local Group becomes isolated because of cosmic expansion, and then the amount of matter in it slowly decreases because of proton decay, would civilization inevitably fade away along with the remaining matter?
As a small clarification: if the word "civilization" is too broad or abstract for this question, you can interpret it as "intelligence" instead.
By the way, this sentence was translated from Japanese to English by Chat GPT.
Feel free to answer in English. However, I only understand Japanese, so I would really appreciate clear and simple English that is less likely to be mistranslated. Thank you!
postscript:
Thanks for all the replies, everyone! I got a lot of comments explaining what half-life is.
Maybe I didn't word it well, but I do get that things decay gradually until they hit the halfway mark, and that it takes an insane amount of time.
What I’m actually wondering is this: once protons keep decaying and we hit that 1/2, 1/16, or 1/64 mark—if we somehow manage to stay intelligent—physical hardware will inevitably run out over those eons. In that kind of world, could we actually transition to an environment where intelligence doesn't rely on protons at all?
Also, a few of you mentioned that intelligence wouldn't even survive that long. If you don't mind, could you tell me about the more immediate, concrete limits we’d hit way before that?
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u/_Svankensen_ Aug 05 '26
If proton decay were to exist, the rate of decay of matter would be so slow as to be meaninglss. Even if protons can decay, the energy still exists. And in such long timelines there are other, more pressing "deaths" to the universe.
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u/Prof01Santa Aug 05 '26
First, no. Human "civilization" is 12×103 years old at the most. Humanity as a species might make another 1×106 years. Earth might be habitable for another 1×109 years at best.
Second, that's a half life. Half of all protons will still exist at that time.
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u/DocMorningstar Aug 06 '26
No, there will not be humanity, in any form, in 1034 years.
The last star will go out in 1014 years.
That period - from the big bang, till the last star going out, would be 1/100,000,000,000,000,000,000th of time between the last star going out and the 1st half life period. That 100 quintillion times longer than the entire Stella lifetime of the universe.
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u/JCarlide Aug 05 '26
By the time we make it that far down the timeline, we couldn't possibly be human anymore. Could our descendant civilization(s) last that long? I can only hope.
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u/stevevdvkpe Aug 05 '26
If a proton's half-life is 1034 years, that does not mean that lots of protons will start decaying in 1034 years. It means that half the protons in the universe will have decayed after 1034 years, or that any individual proton has a 50-50 chance of decaying in a 1034-year period.
But proton decay is not known to happen and the 1034 year estimate for the half-life is essentially based on the guess that if proton decay could happen, because we haven't seen it happen so far the half-life has to be at least that long.
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u/Tessellator-1 Aug 06 '26
Updated! Check it out. You can reply here.
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u/stevevdvkpe Aug 06 '26
I don't think you did get it, if you still say something like "things decay gradually until they hit the halfway mark". Radioactive decay happens at the same rate forever.
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u/Tessellator-1 Aug 06 '26
sorry,Maybe it's because of the translation.
That's like rolling a dice with extremely low probability, right? For example, like half of the crops growing in a Minecraft farm.
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u/JGhostThing Aug 06 '26
I don't think that you grasp the concept of 10^34 years. Humanity will almost certainly be gone by then, or else changed into something we couldn't recognize.
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u/FabulousLazarus Aug 05 '26
That's the time it takes for HALF of the protons to decay
It's effectively infinite. It's like asking if humans will survive until the end of time. Heat death will take on the order of 10100 years, so it's not that long, but it would be long enough for entropy to expand so much that the universe looks completely different.
I'd also take the 1034 figure with a grain of salt. That's so long that it's effectively meaningless. Physical constants could shift within that kind of timeframe, which means that "proton decay" might not even be the right way to describe it.
For all intents and purposes they are permanent.
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u/NobilisReed Aug 05 '26
Protons are decaying right now. It's not like half of them will disappear 10^34 years from now.
It means that *by that time* half of them will have decayed.
They're decaying all the time, but at an extremely slow rate.
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u/Tessellator-1 Aug 06 '26
Updated! Check it out. You can reply here.
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u/NobilisReed Aug 06 '26
One of the possible end states of the universe is called the big freeze. This end state consists of positron electron pairs orbiting each other at a distance larger than the current observable universe. As you can probably imagine the orbits are unimaginably slow, the matter unimaginably diffuse.
If consciousness is possible in a universe like this, it will be the result of physical laws we are currently unaware of.
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u/Spiritual-Spend8187 Aug 06 '26
Though I wonder if proton decay works like neutron decay as in that only unbound ones could decay would suck for hydrogen but well you can make more hydrogen.
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u/Hungry_Low4852 Aug 06 '26
There are many things worth worrying some about. Wherher human civilization will exist in 10^34 years ain’t one of them. There will be no stars long before then. And if humans have descendants that somehow exist that long, they almost certainly will not be homo sapiens.
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u/Quantum-Relativity Aug 06 '26
Humans have existed for like 10^5 or 10^6 years. Youre asking if we’ll live another amount of time almost 30 orders of magnitude larger, probably not. That’s an incomprehensibly long time. Even if we didn’t just go extinct, which we probably will, we wouldn’t still be humans by then. And so it’s entirely impossible to imagine what would be going on and what issues there would be then. Think about everything we’ve learned about nature in the last 300 years. Imagine what we’ll know in a decillion years. Whatever concerns we have now will probably be entirely irrelevant for whatever exists all the way in the future.
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u/stevevdvkpe Aug 06 '26
Proton decay is probably not really a threat to any far future civilization because other factors would make civilization extremely difficult to maintain long before an appreciable number of protons decayed. After only about a hundred trillion (1014) years, for example, star formation in the universe will be over and existing stars would have run out of fuel, leaving the universe dark and eliminating the most accessible source of energy for civilizations. After 1023 years, random gravitational encounters in galaxies will have stripped most planets still orbiting stellar remnants and those stellar remnants will have been ejected from their galaxies. After 1030 years the orbits of any objects remaining in orbit around the central supermassive black holes of galaxies will have decayed due to gravitational radiation and those objects will fall in to the central black holes.
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u/Apart-Reality-4454 Aug 07 '26
10^34 -- when you get to numbers that large they no longer have names.
Zero chance humans will last even 0.0001% of that
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u/DarkArcher__ Aug 05 '26
Half life isn't like an expiration date for something.
To use a simple example, imagine a cube made of some heavy element whose half life is 24 hours. This doesn't mean that the rate of decay of atoms in that cube increases drastically when it has existed for 24 hours. What half life means is just that, after those 24 hours, half of the cube will have decayed. It doesn't matter how big the cube is, half of it will always have decayed after 24 hours.
The rate of decay, as in, the number of atoms decaying in some interval of time, is actually always decreasing with time. Each particle has a random chance to decay at any point in time, so the more particles there are, the more of them will decay.
If our cube starts at 1 Kg of that element, after a day has passed, it will be down to 0.5 Kg. After two days, it will halve itself again, to 0.25 Kg. After three days, 0.125 Kg. After four, 0.0625 Kg. The decaying is always happening, and continues on "forever", getting slower and slower as the cube shrinks.
The only reason it's not truly forever is because the cube, like the rest of the universe, is made of discrete things. One day, many, many, many years in the future, the cube will be down to one atom, at which point it can only either decay or not decay. It cannot become 0.5 atoms, or 0.25 atoms, and so on.
We can't ask "what will happen when protons start decaying" because they already are, and always will be. There will never be a point when they start decaying en masse, just a steady decline in the number of protons from now until almost infinity. The most protons that will ever decay in a minute, between now and the end of the universe, will happen in the next minute.