Everyone has been curious about time travel at least once in their life, usually because of movies like Interstellar and Looper, but most of the articles trying to explain time travel to anyone interested are filled with jargon that almost no one can understand. Here is a simple article to break down the basics of time travel, so that anyone interested in astrophysics can follow along without having to sort through calculus and a long list of vocabulary words.

The first thing you need to know before jumping into this subject is Einstein's Theory of Special Relativity. Albert Einstein said that the speed of light in a vacuum (like space) didn't depend on the motion of the observers. Later, in his published theory of general relativity, he determined that huge objects affect space-time because of gravity.

So basically, the speed of light doesn't depend on the motion of observers, and the gravity of an object affects time.

A good example of this is a black hole and its effect on time because of how extreme the effect is. You would feel normal, but to an observer farther off, time for you is slowing down as time continues normally for them. This is how one could travel into the future, and this happens because of how incredibly dense and massive a black hole is. The problem is, gravity around a black hole is too strong, and the most likely result of being around to travel forward in time is crossing the Event Horizon and never being seen again.

There are a few theories on how we could travel through time, other than the extremely dangerous black hole idea, and my favorite will always be the wormhole theory. Einstein himself suggested the theoretical existence of "bridges" through time and space, and since then, numerous physicists have expanded the theory. Further research has gathered that perhaps tiny wormholes are everywhere, because of something called "quantum entanglement." To sum up quantum entanglement in simple terms, it's where "a pair of objects are bound together. No matter how far they'll fly apart, they will "know each other - even if they are on opposite sides of the galaxy." If we could find hard evidence of these "microwormholes," there could be ways of enlarging them and using them as the bridges through time and space that Einstein suggested. Of course, there are already problems that scientists have thought of concerning this theory, including "a threat of sudden collapse, high levels of radiation and contact with dangerous exotic matter."

So now you know time travel into the future is possible, due to black holes, but is time travel into the past possible?

So far, most scientists say no. Traveling into the past raises many paradoxical issues, like the famous Grandfather Paradox. Another of the many paradoxical issues is the Bootstrap Paradox, also known as the Casual Loop. It's when information casually loops through time but the origin of the information can't be determined.

"An example of this type of paradox involving information is given by Everett: suppose a time traveler copies a mathematical proof from a textbook, then travels back in time to meet the mathematician who first published the proof, at a date prior to publication, and allows the mathematician to simply copy the proof. In this case, the information in the proof has no origin."

Another fact that scientists are using as proof that time travel into the past is impracticable is that no one from the future has visited us yet, as far as we know. For example, Stephen Hawking conducted an experiment and held a party, inviting anyone from the future to join him, and no one showed up. No one from the future has tried to change the world either.

Even Einstein seemed to prove that time travel into the past is impossible with his well-known equation, E = mc Squared. On one hand, it explains the relationship between how much energy is contained in matter, but on the other, it explains the relationship between the mass of an object and its speed. The faster it is, the most energy it requires, and the closer it is to the speed of light, it approaches infinite mass and approaches the requirement of infinite energy to continue.

To travel through time, one has to consider the light barrier. To travel into the future, all you have to do is approach the light barrier, but to travel into the past, you have to break it and that would require greater than infinite energy.

Enough of crushing your dreams of watching the Egyptians build the pyramids, although there is much more out there to prove travel into the past is highly unlikely.

Hopefully, this was simple enough for anyone hoping to learn the basics about time travel due to the fantastic dreams that Hollywood has brought to life. Although travel into the past isn't likely, travel into the future could be possible for humanity with how fast we are advancing in technology. It might not happen with the help of a black hole, because of the risks and how little the reward would be, but we could someday prove the wormhole theory and forever change the way we see the vast dark universe.

The idea of time travel was popularized by H. G. Wells' 1895 novel, "The Time Machine," and finally, after Einstein published his theories in the 20th century, scientists are beginning to think it's not just science fiction after all. It's about time.