Submitted by spiteful_rr_dm_TA t3_11vamkr in askscience
I've heard much about the fate of stars, and what their ultimate deaths will most likely be; be it collapsing into a black hole, exploding, etc. But what about rocky bodies? Suppose Earth doesn't get swallowed by the Sun, what will happen in billions or trillions of years? Will it just always exist, assuming it doesn't get destroyed by outside forces?
So it will basically stick around forever, unless things like protons have an eventual half life?
It's hard to imagine a scenario where protons are absolutely stable. If there is no other process then gravity should be able to make them decay via virtual black holes. But assuming they are absolutely stable you expect the nuclei fuse/split to form iron and nickel over time and stay like that forever.
Can you explain or point to a source for how decay by virtual black holes work? I've never heard of this
Let's look at the weak interaction first, it has a very similar situation: A top quark is so heavy that it can decay to a bottom quark plus a W boson. The W boson then decays to other particles. How can a neutron decay via the weak interaction? It's much lighter than a W boson, it cannot decay to it. It still couples to the associated field, however, and that couples to the decay products of a neutron. You never produce a real W boson in that decay but it allows a neutron to decay to proton+electron+antineutrino. Mathematically we can calculate the probability of this process using virtual particles. They are not real (hence the name), but they have some similarities to the real particles.
Back to gravity: If you shoot two protons at each other with an absurdly high energy then you can create a black hole. The black hole will then decay to a variety of particles, could involve protons but it doesn't have to - black holes don't differentiate between matter and antimatter. Random protons in a cold Earth don't have that energy, but they still interact via gravity, so just like for the W boson case there should be a decay process via virtual black holes. We can't calculate what proton lifetime that will produce (besides "absurdly long") and of course we cannot confirm something experimentally that we don't expect to happen even a single time over the next quadrillion years - but the process should be possible.
Interesting, thanks for the answer!
Yes. As far as we know according to the laws of physics as we understand them, rocky bodies like the Earth do not have a lifespan like stars do, and unless they are consumed by something else, they are likely to drift around forever.
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>In 500 million years the sun will be too luminous for Earth ro be Habitable
Where do you get this number from? It contradicts this:
>At the end of the next 4.8 billion years, the Sun will be about 67% brighter than it is now. In the 1.6 billion years following that, the Sun's luminosity will rise to a lethal 2.2 Lo. (Lo = present Sun.)
https://faculty.wcas.northwestern.edu/infocom/The%20Website/evolution.html
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I'm interested as to where you found that number as all the sources I found indicated 91 billion years.
Good question, tbh, those numbers are from memory from my geology classes back when I studied Geo Science. I may have remembered wrong or those numbers where wrong back then.
Edit: searching a bit more I found this (unverified) answer that might explain the huge difference:
>As the present temperature of the inner core is estimated to be around 5000∘C, this is going to take tens of billions of years.
>The magnetic fields are generated by eddy currents in the outer core, which is a liquid layer about 2,300 km thickness. The inner core is growing at the rate of about 1 mm per year, so it is going to 'freeze over' (i.e. solidify) in about 2.3 billion years. Without its liquid outer core, the Earth's magnetic field shuts down,
If this is correct, the whole process of cooling down will take ~90 Billion years, but the magnetic field will collapse much earlier, making complex life on earth impossible (which will be the case anyway due to increased sun luminosity, but that's another question.)
Well this is very dependent on the specific details of the body.
We've seen that bodies with a large deviation on their surface tend to become tidally locked with what they're orbiting. Ex. The moon became tidally locked with earth and Venus became tidally locked with the sun. Earth and other large planets will probably also eventually become tidally locked as the deviations in their surface slow down their spin and turn a specific face towards the object they're orbiting.
There's always the chance of collisions especially for larger bodies like planets
The sun the body is orbiting will continue growing and for objects close like the earth they'll probably get consumed by it or have their atmosphere shredded off by intense solar radiation as it grows
In most simulations objects orbits tend to get more and more chaotic with time usually ending in them being launched from system
And of course eventually our sun will die. If our star was MUCH more massive it might make a supernova, maybe even a black hole. But for smaller stars like ours it'd probably just release a burst of hot cosmic gas and die.
Basically eventually rocky bodies if not consumed by their star, ejected from the system, or collided with another body, it'll probably sit boringly orbiting a dead star; it also dead with no atmosphere spin or magnetic field.
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Alexander_Schwann t1_jcsdcdb wrote
If the earth manages to avoid being consumed by the Sun dying, it will probably stick around basically forever.
However, eventually (in tens of billions of years) the liquid layers of the Earth's core and mantle will cool and solidify, which will have significant effects on the surface. The Earth's magnetic field will disappear, leaving it unprotected from ionizing radiation and cosmic rays. That will eventually lead to the atmosphere being lost along with all liquid water and Earth will end up looking more like Mars (which we think also once had oceans and an atmosphere). Luckily, we shouldn't have to worry about that for at least 90 billion years.