A lot of people are talking about time travel and it is one of those things that people believe would be possible in the coming future. Well, I'm no scientist. So, I don't know if it is possible scientifically. However, let's assume that it is possible and that a device capable of time travel was made.

What then? Well obviously, it has to be tested. But, how will that be done?

Two options; going into the past, or going into the future.

Let's assume Dr. T invented this device that is capable of time travel. And let's say Dr. T wants to test it by going into the past. However, he knows the consequences of messing with the past. So, he decides to just go 5 minutes back into the past, just to see if it works.

To make this post less complicated, I'll refer to Dr. T of the past as Dr. U.

If Dr. T went 5 minutes into the past, he will see Dr. U pondering over what to do with the machine. And, if he waits for 5 minutes, Dr. U will also make up his mind to go 5 minutes into the past to test his machine. And this can keep looping.

Unless, Dr. T sends a sign to Dr. U telling him that time travel is possible. That would thus tell Dr. U that his machine works and so, after 5 minutes, he won't use his machine. But, by doing that, the time that Dr. T lived in has changed. It is now a world where Dr. T doesn't go into the past.

So, Dr. T can't return to his present, because there will be another Dr. T there. However, he can't stay in this world either, because of Dr. U.

A possible way to counter this would be to ask a friend for help. Let's call him Mr. X.

Now, before Dr. T goes into the past, he tells Mr. X to kill Dr. T after he sends a sign to Dr. U. Thus, if Dr. T dies in the past, Dr. U can live on to be Dr. T and know that the time machine works.

To make things easy,

At 13:15, Present,

Dr. T: Mr. X,  at 13:20, I'll travel back in time (to 13:15) and send Dr. U a sign. As soon as Dr. U gets that sign, he'll tell you. After you find out, look for me in this room, and kill me.

At 13:20, Present,

Dr. T travels back in time.

At 13:15, Past,

Dr. U: Mr. X,  at 13:20, I'll travel back in time (to 13:15) and send Dr. U a sign. As soon as Dr. U gets that sign, he'll tell you. After you find out, look for me in this room, and kill me.

Now that Mr. X knows he has to kill Dr. T, Dr. T sends the sign.

At 13:16, Past,

Dr. U: It worked. Time travel is possible.

Hence, hearing of the success, Mr. X goes to the room to kill Dr. T.

At 13:20, Past,

Dr. U is confident time travel works. Mr. X has killed Dr. T. And Past is now Present.

So, just to check if time travel is possible, scientists will have to do this much thinking. And, the scientist that travels time will have to die, and let his "clone" take over.

But, what if the experiment was to travel in the future?

Going into the future is, as you'd imagine, the opposite of going into the past. The main problem with going into the past is having a clone of you. However, when you travel into the future, for the period of time you skipped, you didn't exist in the world. So, without raising any concerns, you can only travel short distances of time (in the future).

So, if Dr. T goes into the future at 13:15, and he goes to 13:20, he will have to come back to the present between 13:15 and 13:20. But, that means, travelling in the future is quite easy.

However, let's assume Dr. T lives in the year 1900 and travels 100 years into the future.

In 1900, Present,

Dr. T goes into the future.

In 2000, Future,

Dr. T sees a mobile phone and decides to bring it back with him.

In 1900, Present,

The mobile phone is now in this year. Which means, the future of the world has changed. The future that saw the invention of the phone has changed. And so, theoretically speaking, the phone that Dr. T brought back doesn't exist anymore.

So, as you can imagine, time travel is quite paradoxical. And so, I hope they never perfect it. Because, there's no saying how a small change in the past might factor into the world that we live in today.