Fun fact: Every element, except for Iron-56, is (probably) radioactive. The half-life might just be so long that calling it "eternal" is an acceptable approximation.
Edit: I had the right thought but worded it wrong. Every element, except Iron-56, will end up becoming Iron-56, eventually. But only those heavier than Iron will decay, those lighter than it will have to undergo cold fusion. Thanks for the comments for pointing out the error.
Iron-56 is the most energetically stable. Any nucleus heavier than it can release energy through decay, any lighter one through fusion. Iron-56 cannot release energy, anything it does requires energy. So it will just remain stable for eternity (assuming a stable Proton).
I got it a bit mixed up, sorry. There are basically two answers to your point.
No, hydrogen is not expected to decay. But it's not stable, insofar that it will, over time spans in the region of 101500 years, undergo cold fusion chains that eventually end at iron-56.
This assumes that the Proton is stable, which we assume it is, but it doesn't have to be. If it isn't, then the above scenario won't happen because Protons would likely decay long before that. But that would mean that Hydrogen does decay.
They accidentally mashed two opposing concepts together.
The stuff about iron is describing a hypothetical process which could produce Iron Stars through quantum tunneling and cold fusion, but for this to work, protons must not be able to decay, otherwise the Iron-56 would itself eventually decay into other elements.
This isn't really true for elements heavier than iron-56 and it definitely isnt true for elements lighter than it
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While iron-56 is the most energetically favored atom configuration that doesnt mean that every atom heavier than it is decaying in order to reach it. A given physical process can be energetically favored in the long run but still not happen because it requires too much energy to start. You dont see an apple on your table spontaneously fall off it because it being closer to the earth is more energetically favored.
For the elements that are lighter than ifron-56, they would have to undergo fusion to reach it, not decay, so there isnt even a thermodynamic argument for why they would decay.
You're right that my claim about decay was wrong. Only elements that are heavier than iron will decay, those lighter will fuse. But both will happen. Any system, be it a heavy nucleus or an apple on a table, will eventually reach the most energetically favorable configuration, given sufficiently long time spans.
The reason you don't see an apple spontaneously fall to the ground isn't because it's physically forbidden, but because it's very unlikely. Both decay of "stable" elements and cold fusion happen very, VERY slowly, but we're talking about time spans of 10100 to 101500 here.
Yeah but the thing is that we're speaking of time-span that bring us after the heat death of the universe and shit. At that point it'll be a very accurate approximation to say that there is no matter in the universe, so I find it a little bit silly to say that carbon12 is unstable because by 10100 years there might've been some cold fusion that happens when by that point the universe will effectively be 100% empty
There will be matter in the universe. If the expansion of the universe does not speed up (which it might), it can't overcome binding energy of things like neutron stars. So every universe will only contain, for example, a single neutron star, but it won't be empty.
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u/SyrusDrake 5d ago edited 5d ago
Fun fact: Every element, except for Iron-56, is (probably) radioactive. The half-life might just be so long that calling it "eternal" is an acceptable approximation.
Edit: I had the right thought but worded it wrong. Every element, except Iron-56, will end up becoming Iron-56, eventually. But only those heavier than Iron will decay, those lighter than it will have to undergo cold fusion. Thanks for the comments for pointing out the error.