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[Review Request] The Universe Will Not Die a Heat Death (lemmy.world)

submitted 4 months ago by [email protected] to c/[email protected]

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I just wrote this article and I would like your comment:

The Universe Will Not Die a Heat Death

We assume that the universe is expanding according to the Lambda-CDM model with a fixed Lambda constant.

Imagine a central star, like our sun. Two artificial satellites are orbiting this sun in circular orbits in opposite directions. As the universe expands, the orbits of the satellites are elevated, and the satellites thus gain mechanical energy (the sum of potential and kinetic energy). This energy can be released by causing the satellites to collide or by simply having them graze each other. As a result, some of their kinetic energy is converted into heat, which can be radiated away as thermal radiation, and the satellites descend to lower, more inward orbits. The process can then begin anew.

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[–] [email protected] 0 points 4 months ago

It's all about conservation of energy.

In your satellite scenario, the sum of kinetic and potential energy must remain fixed. This means higher orbits are slower orbits. In fact this is observable in man-made satellites that are moved to higher or lower orbits. There is no free ride.

In the "heat death" of the universe scenario, the total amount of energy in the universe is conserved (it is finite) but the volume of the universe keeps growing. On a long enough time scale the universe's average energy per unit volume approaches zero.

[–] [email protected] 0 points 4 months ago

As the universe expands, the orbits of the satellites are elevated,

Gravity is much stronger than the effect of expansion at that scale. The universe expansion is not changing any orbits.

[–] [email protected] 0 points 4 months ago (1 children)

entropy is a bitch. youre not thinking long term

[–] [email protected] 0 points 4 months ago (1 children)

Yeah I guess there are some phenomenons that I haven't considered. But are they really strong enough to stop the game?

I have already excluded that frame-dragging/emission of gravitational waves stops the game, because the emission of gravitational waves reduces the energy from the system, but the effect is stronger if objects are closer by. when the distance between them is larger, gravitational waves become negligible. hubble expansion, on the other hand, becomes stronger on larger scales. so at some point, it's larger than the loss due to gravitational waves.

explain entropy though, where's thermodynamics in the game?

[–] [email protected] 0 points 4 months ago (1 children)

am ignorant layman .. so.. happy to be corrected

as i understand it the universe is a closed system, right? no more energy is being put into it. yet its expanding constantly. that expanision isnt at the edges.. its everything

at some far off point everything that exists will be so far apart from everything else it will come down to the decay of atoms/particles themselves. thats the heat death

[–] [email protected] 0 points 4 months ago

As a lay woman, this is what I thought too. Expansion keeps going until 0°K is reached for everything. And also happy to be enlightened if this is outdated, muddled, just plain wrong.