Understanding Entropy and Hawking Radiation in Black Holes

In summary, the conversation is about trying to understand Hawking radiation and its relationship to entropy. The equation for entropy is discussed, with a question about the meaning of Q_rev and its units. It is determined that Q_rev is in Joules and T is in Kelvin. The conversation ends with a clarification about the units of entropy and a thank you.
  • #1
Stephanus
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Dear PF Forum,
I'm trying to make sense about Hawking radiation in Black Hole. And that leads me into entropy.
I read this equation in
https://en.wikipedia.org/wiki/Entropy
Entropy.JPG

What does that mean?
S is the change of Entropy
What does Qrev mean there?
Is it in Calorie? then Joule?
T, I think is in Kelvin.
 
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  • #2
Q_rev is the heating change for a reversible process. Googling "units of entropy" returns J/K, so I'm going to say it's in Joules. T, being the absolute temperature, has to be in kelvin.
 
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  • #3
BiGyElLoWhAt said:
Q_rev is the heating change for a reversible process. Googling "units of entropy" returns J/K, so I'm going to say it's in Joules. T, being the absolute temperature, has to be in kelvin.
Joule per temperature, ...? Ok, I'll try to imagine it. Thanks.
 

1. What is entropy?

Entropy is a measure of the disorder or randomness in a system. In physics, it is often referred to as the measure of the amount of energy that is unavailable for work in a thermodynamic process.

2. How does entropy relate to Hawking radiation?

Hawking radiation is a process in which black holes emit particles and lose energy. Entropy is used to describe the increase in the randomness of the particles emitted by the black hole, as the black hole's entropy decreases.

3. What is the relationship between entropy and the second law of thermodynamics?

The second law of thermodynamics states that the total entropy of a closed system will always increase over time. This is because any physical process will naturally lead to an increase in disorder or randomness, and entropy is a measure of this disorder.

4. How does Hawking radiation affect the overall entropy of a black hole?

Hawking radiation causes black holes to lose energy and therefore decrease in mass. As a result, the black hole's entropy also decreases, since its mass is directly proportional to its entropy. This is consistent with the second law of thermodynamics, as the total entropy of the black hole and its surroundings will still increase over time.

5. Can Hawking radiation eventually cause a black hole to disappear?

In theory, yes. As a black hole loses energy and mass through Hawking radiation, it will eventually reach a point where it can no longer sustain itself and will disappear. This process is known as black hole evaporation. However, for most black holes, this process would take an incredibly long time, on the order of 10^67 years for a black hole with the mass of our sun.

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