Assumption: Universal entropy results in heat death(no further fusion radiation). Radioactive elements must decay before true heat death. There is time for this to occur for a significant proportion of radioactive elements before they are absorbed into the energies of the BH clusters that inevitably develop.

Challenge I: Provide approximate of the ‘cold’ matter/s that would be left after all radioactive elements have decayed-(mineral types and comparitive proportions)

Riff-in-Thyme said:

Assumption: Universal entropy results in heat death(no further fusion radiation). Radioactive elements must decay before true heat death. There is time for this to occur for a significant proportion of radioactive elements before they are absorbed into the energies of the BH clusters that inevitably develop.

Challenge I: Provide approximate of the ‘cold’ matter/s that would be left after all radioactive elements have decayed-(mineral types and comparative proportions)

Then the mineral types and comparative proportions on any surviving planets and brown dwarfs would still be pretty much the same as today’s, only colder. For larger planets and brown dwarfs the dominant minerals in decreasing order of abundance would be H2 (solid because of the low temperature), H2O, CH4, NH3, and then hydrides of aluminium, iron, silicon and sulphur. I’d need to check Gibbs free energy to see how often you’d expect to see N2, CO2 and oxides, but for planets expect proportions similar to today’s.

For stars becoming white dwarfs the final stage would be degenerate matter (no molecules) composed primarily of carbon, nitrogen and oxygen. Neutron stars would have no minerals as such.

There are two levels of uncertainty here.
1. Which elements are radioactive?
2. Do protons decay?

1. I discovered the first level of uncertainty when looking for the isotope with the longest half-life. New longer-lived unstable isotopes are still being discovered. It turns out that nobody knows which elements are unstable on a long-enough timescale. Dozens of elements that are normally considered to be stable are “potentially” unstable subject to spontaneous fission on sufficiently long timescales. Nobody knows for sure whether they really are unstable.
https://en.wikipedia.org/wiki/Stable_isotope#Still-unobserved_decay
Let’s say that all elements heavier than niobium are unstable, and others are stable.

2. If supersymmetry exists then protons probably decay. If that happens then protons decay to positrons that annihilate with electrons to give gamma rays that cool towards zero Kelvin. All that would be left would be a cooling collection of photons and neutrinos (and dark matter perhaps), no minerals would exist. So far, physics experiments have shown no signs of proton decay and no sign of supersymmetry.

I should also add that metallic hydrogen inside cooled large planets and brown dwarfs will also become a form of degenerate matter. This is created by pressure from above. No molecules as such.

> I’d need to check Gibbs free energy to see how often you’d expect to see N2, CO2 and oxides

eg. 2H2O + CH4 is more stable than CO2 + 4H2, so CO2 would be a rare mineral in heavy planets and brown dwarfs.

Have not taken into account destabilisation of planetary orbits by gravitational interactions. I’m far from sure how many planets would avoid being swallowed by stars.

mollwollfumble said:

> I’d need to check Gibbs free energy to see how often you’d expect to see N2, CO2 and oxides

eg. 2H2O + CH4 is more stable than CO2 + 4H2, so CO2 would be a rare mineral in heavy planets and brown dwarfs.

Have not taken into account destabilisation of planetary orbits by gravitational interactions. I’m far from sure how many planets would avoid being swallowed by stars.

Thanks Moll, you’ve made a good start. The basic direction here is to estimate which compounds would be most stable and then to evaluate what components have been left if you consider the universes compounds as being chips(resistor/diode/capacitor-whatever) in a circuit. ie, which components survive and which fail