Time travel

It introduces more problems than it solves.

It would violate some very fundamental laws of Physics. To give an example, the second law of thermodynamics. It states that the entropy (number of possible states a given thing can occupy) of an isolated system always increases with time.

It it wasn’t for this law, physical laws would work the same way regardless of the direction of time. In a sense, this law of thermodynamics acts like an arrow of time, for we can say that time has passed when we see entropy increasing.

It is possible to decrease entropy in localised regions, for example, humans are a product of decreased entropy, but the entropy of the whole Universe is always increasing.

What time travel would suggest is that entropy increases over a long period of time, but may not be satisfied in localised periods of time. Instead of entropy decreasing in a particular space at a moment, entropy could be decreasing for a certain finite amount of time, before increasing beyond its original value at some time in the future.

This simply does not happen, because it would probably violate a philosophical law too – it’s called causality (note that it’s not casuality or casualty, which is just wrong spelling). In simple terms, it states that cause leads to effect, and not the other way around.

For example, if you subject a charge to an electric field, it will experience a force. So the cause is the subjection of a charge to an electric field, and the effect is experiencing a force. It is not true that if the charge is experiencing a force, it will be subjected to an electric field. That’s what cause and effect is, simply.

And the word “travel” is also a misnomer. Time is not like space, something you have to travel through. Rather, time is something you experience. You may experience time faster relative to another person experiencing time, which is what we usually call “travelling” through time.

Now that that’s out of the way, we can come to the fun part: paradoxes. The grandfather paradox immediately comes to mind. And I choose to believe in the following resolution of this paradox:

When a person travels to the past and kills their grandfather, there’s no real paradox. The state of the Universe becomes different to what it was for the time traveller from the moment they arrive in the past. They’re effectively rewriting history, albeit in a smaller scale. The copy of themselves they would see (if they lived long enough, that is) would likely be different from their own selves, because for this copy, the time traveller has changed the past.

Now, after doing so, if the time traveller comes back to the future – and this is allowed in Physics (it’s called time dilation) – they will see the future caused by the changes made by them to the past. Their original future is lost as soon as they travel to the past, and since the world is chaotic, small changes in the past can produce large changes in the future.

Another aspect of time travel is the travelling of information. There was a movie called Frequency released in 1999, that had to do specifically with the travelling of information through time. You can check it out on Wikipedia if you want to read about it, so I’m not going to link to it here.

To summarise, time travel is a risky business, and even though it may enable doing some really, really cool things, it’s not worth the confusion and unintended consequences. If you really want to experience time travel first hand, watch a movie released in 2004 called Primer. It’s sure to mess up your mind big time, so I’ve warned you.