Entropy and Time Travel

We know that time is relative to the observer in order to keep the principle, which is that light shall always travel at a constant speed. Relatively, yes, this means that travelling to the future of another observer is possible, by travelling at speeds closer to the speed of light, or by experiencing lower gravity. However, what I will deny is that travelling to the past is, according to our current understanding of physical laws, impossible, as time flows according to entropy.

Entropy might be a new concept to us. It is a measure of energy over temperature, which may define how “chaotic” the state of matter is in; the larger the entropy, the more disorderly it is. According to the second law of thermodynamics (which we sadly skipped in class), any system will tend toward higher entropy. Entropy can only increase, and there is no known way to revert a system into a more orderly state. An easy example is that you cannot un-mix a homogenous sugar solution.

That said, time itself might be called as imaginary, a method to explain this system that tend toward higher entropy. There is only now, and a span of time between events, where the direction of this time, in definition, is whichever direction the system is heading toward higher entropy. This provides a clear direction of time, as entropy cannot lower.

One may argue that time travel may not happen, for the simple reason that time is merely an illusion, a concept connected with entropy. However, by only using the current definition of time, it may not move “backward”, as a system will always increase in entropy, and thus time travel backward may not happen.

Sources

https://www.youtube.com/watch?v=yKbJ9leUNDE

http://www.johnagowan.org/tetra11.html

Inside a Black Hole

As I descend through the spiral of hot gases spiraling the black hole, and experiencing time dilation due to the immense gravity near the event horizon, those may be the last things I see. Apart from being ripped apart and thus not being able to see anything, there is also a reason why there is seemingly nothing inside black holes, which is because there is only a singularity inside a black hole.

A singularity is a mass compressed in a volume so small that it would warp space-time into a “hole” straight through; according to the way gravity works, this means that no matter may escape (apart from using the theory of Hawking radiation, in which black holes very slowly radiate away its mass). Inside the singularity, matter will be ripped apart due to this extreme warping.

Past the event horizon, it seems that physics as we know it fail. As matter becomes ripped apart, it has no way of returning outside, which is why we cannot see anything inside. Inside the singularity, I expect to see everything the black hole has ever eaten. However, at this point they are indiscernible; “perfectly featureless”. Only the mass and the state of rotation the matter had before falling would be kept inside the singularity.

Of course, as the physics itself inside the black hole may be different, the singularity might not be what physicists expect it to be. Perhaps, according to another theory, we may see a parallel universe inside, or a different point in space-time, as the black hole may have a counterpart: the white hole, which spits matter out.

Either perfectly featureless, or if there is a whole other universe inside, with our current understanding, one thing is clear. We could only theorize what the inside of a black hole look like. Certainly it is very different from what we understand as space-time.

Sources:

http://www.hawking.org.uk/into-a-black-hole.html

http://www.iflscience.com/physics/what-white-hole/