Hydrogen, eternal element?

[sunshaker]

http://www.scienceforums.net/topic/102124-why-do-elements-want-to-achieve-a-stable-state/

 

I was just reading above thread, wanted to ask a question.

 

@swansont

 

Stable = does not decay. Unstable = decays. That's a fairly strict border.

"Not observed to decay" is a little bit fuzzy, but that pushes lifetimes out to at least trillions of years (since we can and have identified isotopes with billion year half-lives)

I understand that lead & iron are classed as stable elements,

but will eventually decay to Hydrogen/Helium. but will take trillions of years?

 

I believe Hydrogen is a stable element that would never decay?

 

So when all the stars/planets burn out, would their cold cores eventually decay to hydrogen/helium over trillions upon trillions of years?

 

If the above all do decay to Hydrogen/helium, would these now very dispersed hydrogen atoms, eventually have the gravity to create a singularity & ignite a new universe?

 

Or would these hydrogen/helium atoms eventually just form new stars/galaxies?

 

If all the hydrogen(from old decayed universe) once again formed new stars/galaxies, They would be spread out across the new universe, forming where the old hydrogen had gravitated/condensed enough to ignite stars/galaxies,

Would this look any different to our universe looks now?

 

 

 

[Sensei]

I understand that lead & iron are classed as stable elements,

but will eventually decay to Hydrogen/Helium. but will take trillions of years?

What is currently accepted (from observations), unstable isotope, or unstable particle,

spontaneously decays only when it has more mass-energy prior decay than after decay.

 

Sum the all mass-energy of protons and neutrons together:

 

[math]m_{total}=m_p * Z + m_n * (A-Z)[/math]

 

[math]m_p = 938.272 MeV/c^2[/math]

 

[math]m_n = 939.565 MeV/c^2[/math]

 

And then subtract from it mass of Lead or Iron or whatever else you would like to examine.

You will have pretty large value, of missing energy (which was released during fusion).

It's called nuclear binding energy.

https://en.wikipedia.org/wiki/Nuclear_binding_energy

 

 

I understand that lead & iron are classed as stable elements,

There is dozen of unstable isotopes of Lead and Iron. Just some few are stable..

 

Bombard stable isotope by f.e. free neutrons,

and neutron can disintegrate isotope,

or there could be neutron capture,

and creation of unstable isotope, which will decay in future.

Edited January 5, 2017 by Sensei

[StringJunky]

Here's a few scenarios:

 

Future of an expanding universe - Wiki

Edited January 5, 2017 by StringJunky

[swansont]

Hydrogen and helium tend to fuse, but not without end, and heavy elements decay, but not all the way to hydrogen. In the vicinity of iron you have the highest nuclear binding energy per nucleon. That's where fusion ends.

 

As I said in the other thread, we know of unstable isotopes with billion year half-lives. Isotopes we call stable have to at least be much longer-lived than that, or we'd notice them decaying.

[sunshaker]

Here's a few scenarios:

 

Future of an expanding universe - Wiki

Cheers, interesting link,

 

@swansont, Sensi, from what I understand, you are saying 56fe will never decay, would 56fe last all of eternity?

 

I read in stringjunky's link about quantum tunneling, which suggests will happen to these iron star cores, turning them into black holes, which would over time evaporate via Hawkins radiation?

 

 

Collapse of iron star to black hole[edit] 10¹⁰²⁶ to 10¹⁰⁷⁶ years from now

Quantum tunnelling should also turn large objects into black holes. Depending on the assumptions made, the time this takes to happen can be calculated as from 10¹⁰²⁶ years to 10¹⁰⁷⁶ years. Quantum tunnelling may also make iron stars collapse into neutron stars in around 10¹⁰⁷⁶ years.^[12]

But if protons do eventually decay, would this mean that 56fe would also eventually decay? or does it mean that while protons are in the form of 56fe, they will not decay, even if free protons do decay to leptons?

 

If protons do decay, they would turn to leptons, and if 56fe does not decay, and has leptons are subject to the other three fundamental interactions: gravitation,electromagnetism and the weak interaction, Would these iron remnants attract these decay products leptons/protons etc.

which over time, would result in stars forming around these super dense iron cores? similar to galaxies around super black holes?

 

Also I was wondering, when all/most matter has decayed, how would this ,effect space-time, stars/galaxies/black holes twist and bend space-time, would this result in a flatter smoother universe, that would make it easier for these decay products to gravitate together?

[swansont]

Whether a free proton decays is still open to question, but the expected lifetime of the models used is quite long — at least 10³¹ years. A bound proton is in an even lower energy state, and even less likely to undergo that same decay.