# Tag Info

### What would happen if I accelerated to 0.999c seconds before the heat death of the universe?

(1) Heat death is no switch that flips, it's a gradual process. You can't time it sharply. (2) There is no absolute time in special relativity, so it does make sense that it takes different times for ...
• 9,708
Accepted

### Why is the second law of thermodynamics not symmetric with respect to time reversal?

The arrow of time in thermodynamics is statistical. Suppose you have a deterministic system that maps from states that can have character $X$ or character $Y$, to other states that can have character \$...
• 8,972

### What would happen if I accelerated to 0.999c seconds before the heat death of the universe?

There are a few tiny kinks on your logic, but we can soon straighten them out! In no particular order... You are implicitly assuming that the heat death occurs everywhere in the frame of the '...
• 18.8k

### Where does the irreversiblity came from if all the fundamental interaction are reversible?

There's a distinction between microscopic reversibility and macroscopic reversibility. Or if you will, a difference between something being irreversible in theory versus irreversible in practice. (Or ...
• 300

### Local decrease of entropy, does it require life?

No life needed for this. All you need is for heat to flow away from the local region. It will carry entropy with it. Example: make yourself a cup of coffee. Put the cup on a table and wait while it ...

### Entropy of the earth decreased since pre-biological times?

Entropy on the Earth has decreased over time as more and more structures and patterns have been added. The entropy of the earth has decreased over time due to the fact that it has cooled down ...
• 25.3k

### Entropy of the earth decreased since pre-biological times?

To differentiate itself from its surroundings, any living organism (no matter how simple) must decrease its entropy. Or, at least, it must ensure that its entropy increases more slowly than its ...
• 33.9k
Accepted

• 3,987
Accepted

### How can it be shown that a system's entropy is reduced by cooling it?

You're looking at it the wrong way. If your equation was $$S=\frac{some constant}{T}$$ I would agree that it says the entropy increases when T decreases. But we definitely don't have something of that ...
Accepted

### Is time still (frozen) for a single isolated particle?

You can certainly imagine such a Universe with one lonely structureless and cold particle, interacting with nothing and living in some eternal and unchanging spacetime. Of course such a Universe it is ...
• 34.3k

### Where does the irreversiblity came from if all the fundamental interaction are reversible?

then where does the irreversibility come from? You mean macroscopic irreversibility, our inability to set up or observe a macroscopic process that retraces past states of a known spontaneously ...
• 28.4k

### Local decrease of entropy, does it require life?

It happens about 50 times in a second in any internal combustion engine, including cars. Without life. Life has no specific meaning in thermodynamical sense.
• 7,839
Because the entropy in this notes is defined in terms of the heat transfer: $$dS=\left(\frac{\delta Q}{T}\right)_{int, rev},$$ which is the increase of the internal energy not associated with work. ...