76
votes
How do different definitions of entropy connect with each other?
Your concern about the too many definitions of entropy is well-founded. Unfortunately, even in the scientific literature, there is an embarrassing confusion on such an issue. Even in the SE sites, the ...
71
votes
Accepted
Is there any known thing or physical object that absolutely cannot be destroyed?
The fundamental laws of physics are time reversible. So if something cannot be destroyed then it follows that it cannot be created. And if it cannot be created then either it doesn't exist or it has ...
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65
votes
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Does entropy depend on the observer?
E.T. Jaynes agrees with you, and luckily he is a good guy to have on your side:
From this we see that entropy is an anthropomorphic concept, not only
in the well-known statistical sense that it ...
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63
votes
Accepted
Is there a physical limit to data transfer rate?
tl;dr- The maximum data rate you're looking for would be called the maximum entropy flux. Realistically speaking, we don't know nearly enough about physics yet to meaningfully predict such a thing.
...
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48
votes
Accepted
Why is the information paradox restricted to black holes?
(The answers by Mark H and B.fox were posted while this one was being written. This answer says the same thing in different words, but I went ahead and posted it anyway because sometimes saying the ...
- 55k
42
votes
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Super Fast Message
Good question! Imagine sweeping the bat signal really quickly across Mars. You could totally have it move faster than the speed of light across the surface!
But now imagine that you are standing on ...
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40
votes
Accepted
Can Second Law of Thermodynamics / Entropy override Newton's Laws?
Can the Second Law of Thermodynamics / Entropy override Newton's Laws?
No. In the example given, every particle obeys Newton's laws. There is no particle that is not obeying $F=ma$.
From the ...
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38
votes
How does light, which is an electromagnetic wave, carry information?
You talk about light as if it were a person carrying a clip board writing down things on its way to you. It is a physical phenomenon that gets affected as it propagates.
Depending on the various ...
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33
votes
Is there a physical limit to data transfer rate?
The Shannon-Hartley theorem tells you what the maximum data rate of a communications channel is, given the bandwidth.
$$
C = B \log_2\left(1+\frac{S}{N}\right)
$$
Where $C$ is the data rate in bits ...
- 471
31
votes
Does information have mass?
Information does not have mass, but the physical materials containing that information may. For example, if one wishes to have robust storage of that information, one may choose a structure which ...
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31
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Imagining Graham's number in your head collapses your head to a black hole
Simply put, what's stated in the video is misleading to an extent that it's fair to say it's wrong.
Ignoring problems of how you define the word 'imagining' (this is physics stack exchange, after all),...
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28
votes
Why is information "lost" when it got into a black hole?
In classical physics, there is no black hole information loss paradox: the information is lost, and that's all there is to it. No paradox. (See Ben Crowell's answer.)
The famous "black hole ...
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28
votes
Does information have mass?
Claude Shannon proposed the idea of information entropy, which is essentially about how much uncertainty you have about different outcomes. For example, when I read 100 bytes from a hard drive, I ...
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26
votes
Is the second law of thermodynamics even a law?
I'm going to specifically address the two concepts you brought up in your second point:
The Poincare recurrence theorem
In layman's terms, this theorem reads: "For any system in a large class of ...
- 35.8k
26
votes
Does information have mass?
Yes
The mass of information can be inferred from the Bekenstein Bound. However, it depends on the spatial extent of the information: a larger space requires less mass per bit. But don't worry......
- 2,772
26
votes
How do different definitions of entropy connect with each other?
The reason why Entropy has so many descriptions is not because it was designed to. Nobody started out with all of those things called Entropy.
Entropy started off with one thing. And then a bunch of ...
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25
votes
Imagining Graham's number in your head collapses your head to a black hole
Bekenstein Bound
The Numberphile mathematicians were clearly describing an explicit representation of the bits in Graham's number, rather than any symbolic one (obviously, just writing "G" ...
- 2,772
23
votes
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The Journey of an Electromagnetic Wave Exiting a Router
The router converts this WiFi signal into a long-range signal. This signal can traverse the length of the Earth.
No, the route usually goes via more than one router, and the signal only has to reach ...
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22
votes
Does a random number generator have real entropy?
There are several definitions of entropy in physics, based on the work of Claussius, Gibbs, Boltzmann, and others. Of particular interest here is Boltzmann's definition, which relates entropy to (the ...
- 463
21
votes
Why is the information paradox restricted to black holes?
When Dr. Hawking talks about information being destroyed, he is talking about the erasure of all evidence that the information ever existed. In the case of burning a written letter, you could track ...
- 24.7k
19
votes
How does light, which is an electromagnetic wave, carry information?
When a photon hit the retina, it only has two pieces of information:
Its wave length and its position/direction. That is all.
But it is not alone. We are bombarded with billions of photons every ...
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18
votes
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Information entropy and physics correlation
I hope that my answers below will all be helpful.
There are more than one way to think about this, but the one I find most helpful is to think of thermodynamic entropy as a specific instance of ...
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17
votes
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Contradictions caused by moving faster than light
In order for an idea to lead to a logical contradiction, there needs to be something that it contradicts. Since the idea of faster than light travel is logically conceivable, it has no self-...
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17
votes
Is there any known thing or physical object that absolutely cannot be destroyed?
The word "destroyed" doesn't bear a lot of mean in a generic scientific context, in other words; you left the word "destroyed" to be open for interpretation.
For example:
When you ...
- 271
16
votes
Accepted
Can data be transferred using the strong force?
Both the EM force and gravity are long range forces. The mediator is massless.
Now the gluon is massless too. So far so good. But gluons and quarks live in confinement. That is why the strong force ...
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15
votes
Contradictions caused by moving faster than light
Maximal Ideal's answer looks at the problem from the standpoint of special relativity, but this wouldn't convince someone who doubts the truth of SR (and, indeed, relativity is just a theoretical ...
- 3,785
14
votes
What precisely does it mean for "information to not travel faster than the speed of light"?
An example might help. While not giving a "strict definition," it might be a step toward constructing one. (I think I am remembering this from Hans Reichenbach's classic Philosophy of Space and Time.) ...
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14
votes
Is the second law of thermodynamics even a law?
Suppose you flip a fair coin $N=10$ times. You would expect the number of heads $n_H$ not to differ too much from the number of tails $n_T = N - n_H$, but you wouldn't be surprised if you got, for ...
- 8,517
14
votes
Does a random number generator have real entropy?
Are you asking if running an algorithm on your laptop generates entropy? Yes, it does. It is an irreversible process. The electronics requires electrical energy and converts it into heat. Is that the ...
- 3,137
14
votes
Accepted
Does a random number generator have real entropy?
In thermodynamics, entropy is defined for gases.
In thermodynamics, entropy is defined for a state of knowledge about the microscopic particle configurations in a system—the positions, velocities, ...
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