If the Hawking radiation temp of a black hole is less that CMB temp how can it net evaporate?

[steve_bank]

Trying to shoehorn osmology into LOT is a good exercise but doesn't resolve anything.



Thermal death I assume would mean no atoms. Atoms represent potential energy, E = mc^2.

LOT arose out of observation in the 19th century in the development of steam engines and power.People tried to make perpetual motion machines.

Heat, work, energy, are equivalent.
Within a steam engine matter and energy can't be created or destroyed.
Energy-mas in, energy-mass-work in the engine, and energy-work-mass out must balance.
Within the engine there is energy not available to do work.

It is not stated as being true, it is said no exceptions have been found.

Applying LOT to the BB as an engine doing work, do you assume a finite amount of energy in the initial conditions?
The work being done with motion of stars and galaxies has to be reflected as energy in the initial conditions, I would think.

 

[steve_bank]

Sorry Loren, tunnel diodes do not spontaneously create matter. The doping and materials creates a condition where current can 'tunnel' around the potential barrier.

https://en.wikipedia.org/wiki/Tunnel_diode
https://en.wikipedia.org/wiki/Quantum_tunnelling

The tunnel diode doesn't create matter. It uses the already-existing creation of matter to do the tunneling.

I do not an accept and absolute end of the universe scenario.

What you accept or don't accept has nothing to do with reality.

As the initial post referencing tunnel diodes appears to have vanished I have no response.

 

[skepticalbip]

Thermal death I assume would mean no atoms. Atoms represent potential energy, E = mc^2.

Exactly. That video presented a universe with nothing but a uniform distribution of radiation that was left after neutrons, protons, etc. decayed. Free neutrons do decay in about 15 minutes, proton decay is hypothetical but would be necessary for a grand unified field theory.

An interesting question for me is why do free neutrons decay so quickly but are so stable when in an atom's nucleus.

 

[repoman]

Thermal death I assume would mean no atoms. Atoms represent potential energy, E = mc^2.

Exactly. That video presented a universe with nothing but a uniform distribution of radiation that was left after neutrons, protons, etc. decayed. Free neutrons do decay in about 15 minutes, proton decay is hypothetical but would be necessary for a grand unified field theory.

An interesting question for me is why do free neutrons decay so quickly but are so stable when in an atom's nucleus.

My guess is that protons become neutrons and vice versa in the nucleus through pions faster than a neutron can decay.

https://en.wikipedia.org/wiki/Nuclear_force#The_nuclear_force_as_a_residual_of_the_strong_force

 

[bilby]

A universe that contains only photons of equal energy has no energy gradients and therefore no capacity for change. As photons travel at c, and therefore do not experience time in their reference frame; And as no other reference frames are in use, the concept of time no longer applies once the universe reaches this state. It's not just the end of physical interactions, but also the end of time itself.

Whether such a state is possible, given the existence of quantum fluctuations that create particles constantly in 'empty' space is an interesting question, but not one I am qualified to answer - I suspect that the answer will depend upon exactly how a future GUT reconciles QFT and Special Relativity.

 

[Loren Pechtel]

Thermal death I assume would mean no atoms. Atoms represent potential energy, E = mc^2.

Exactly. That video presented a universe with nothing but a uniform distribution of radiation that was left after neutrons, protons, etc. decayed. Free neutrons do decay in about 15 minutes, proton decay is hypothetical but would be necessary for a grand unified field theory.

An interesting question for me is why do free neutrons decay so quickly but are so stable when in an atom's nucleus.

Such reactions are driven by the energy states. All reactions actually work both ways (although a reaction that yields many products is for all practical purposes irreversible as you'll basically never find all the parts in one place) and what they do is driven by energy levels. All reactions also have an amount of energy required to initiate them. When the initiation energy is low the reaction proceeds very quickly, when it is high it proceeds slowly.

Note that the situation can change the energy balance and thus the favored result. Lets consider plain old water. It's room temperature--water is a liquid, isn't it? Nope--it's actually a combination of solid, liquid and gas. The solid phase is insignificant under these conditions but the gas phase is not--that's why water evaporates.

Lets play with the pressure and see what happens--run it down to about 3% of atmospheric pressure (I'm reading all these numbers off a graph, they're not going to be very accurate) and now the gaseous phase dominates--the water is boiling. Same water, all we did is change the outside conditions. Lets go the other way--this time we will have to go up to about 10,000 atmospheres and we will find the water freezes. (And the ice will change form three times as you run the pressure up even higher.)

Playing with the temperature will get the same result although in this case there are fewer phase changes in the frozen area.

In the nucleus we have the strong nuclear force trying to stick things together. On it's own a neutron goes to a lower energy state when it decays but inside a nucleus this will lower the binding energy of the nucleus and thus becomes a disfavored reaction in most cases. (Note that in nuclei with excess neutrons this changes and the reaction isn't disfavored as much. We call such nuclei radioactive--specifically, they are beta emitters.)

- - - Updated - - -

A universe that contains only photons of equal energy has no energy gradients and therefore no capacity for change. As photons travel at c, and therefore do not experience time in their reference frame; And as no other reference frames are in use, the concept of time no longer applies once the universe reaches this state. It's not just the end of physical interactions, but also the end of time itself.

Whether such a state is possible, given the existence of quantum fluctuations that create particles constantly in 'empty' space is an interesting question, but not one I am qualified to answer - I suspect that the answer will depend upon exactly how a future GUT reconciles QFT and Special Relativity.

The universe is still expanding so those photons are still redshifting, there still is change.

 

[Bomb#20]

Exactly. That video presented a universe with nothing but a uniform distribution of radiation that was left after neutrons, protons, etc. decayed. Free neutrons do decay in about 15 minutes, proton decay is hypothetical but would be necessary for a grand unified field theory.

An interesting question for me is why do free neutrons decay so quickly but are so stable when in an atom's nucleus.

Well, depending on which nucleus it is, neutrons in a nucleus aren't all that stable. Lots of neutrons decay faster in a nucleus than on their own. A neutron in a carbon-15 nucleus (What the heck is carbon-15, you may ask? This is why.) will decay in about two and a half seconds. So your question needs to specify which nucleus. The general principles are the same but the devil is in the details.

The reason a neutron is intrinsically unstable is because it can transform into an electron, a neutrino and a proton, and the total energy of the three is a little lower than a neutron's energy. But when that unstable neutron is bound in a deuterium nucleus, if it were to decay, the result would be an electron, a neutrino and a nucleus with two protons, i.e. helium-2. Helium-2 is extremely unstable; it decays in less than a nanosecond. Its decay energy is greater than the decay energy of a neutron. So the reason a neutron is stable in deuterium is in effect because in order to decay it would have to pay for the helium-2 decay, and it can't afford it.

ETA: I see Loren beat me to it.