4 feb. 2014

Mad about time I. Time travel to the future

The concept of the time is something that is with us during all our life. We are born, we grow and we die… all the time with the time than seems to run in one direction with the same speed.
But, can it be possible to change its direction or to increase its speed? I mean. Can we travel to the past or to the future?


Based in the theory of the relativity proposed by Einstein in the beginning of the XX century, it is indeed possible to travel to the future.
This affirmation is linked with the concept of the time. Back to the XVII century, Newton had said that the time flows regardless of living beings perception. Nevertheless, our perception of the time is different than the time really is.
We know that the time flows but we know that because we realize about changes in something. For example, we can see the movements of the clock or the changes in the position of the sun and the stars. Or we can see changes in our body as the breathing or the heart pulsation. Or if we feel thirsty or tired in some time we know that the time had flown to reach this situation.
Generally, the time does not depend of the place where we live. However, sometimes, we feel that the time runs slower or faster than other situations. In these cases we know that, at least the clocks will advance always in the same way with the same velocity… but this is not true.
Einstein says that if you move, time will run slower even if you cannot realize about this. What about if you move at higher speeds? Then you can start to realize that the world would seem to move faster and for the people who look at you, they would start to see your movements very slow.
If you can travel to a speed close to 300 million of kilometres per second (light speed), the time around you would move incredibly fast while for them, you and the clocks that travel with you would move very very slow almost quiet. This is a time travel to the future.
Has somebody travelled to the future?
Yes.
When you travel regardless of your speed with respect to other person that stays quiet, you travel to the future. The problem is that this future is very close to the present so in practical terms, maybe this is not the travel that you were dreaming of?
Well, let us see at which speeds this travel can be closer to our dreams.
The dilation of the time is measured by the following equation:
to is the time change for the people not travelling with you (think in a second for them). t is the time change (think in a second for you) for you travelling at an speed v.
If v is the half of light speed c, each second (to) of the quiet people is 1.5 seconds (t) of you. In other words, your seconds would be longer than their seconds. If they live one year, you live 10 months and a half. If you increase v, your seconds would be longer. If you could travel at 99%, 99.9% or 99.99%, of c, one of your years would be 7, 22 and 71 years of the quiet people! In a second you can travel 7 or 22 minutes or even more than 1 hour to the future.
Now the problem is reduced to be able to travel at those speeds. How to do that?
The highest speed for a machine to travel has been 0.0055% c for space probes. I am sorry; these are the bad news because these speeds are too far away for our wishes to travel to the future.
However, there are atomic particles that can perform these travels because they move to speeds close to the light speed. Muons are an example of them. These particles are the product of the interaction of cosmic rays with particles in the Earth atmosphere that reach the Earth’s surface when they are not supposed to do it because they are not supposed to live so long! The situation is that they travel very fast so they can reach the surface in their future when they are supposed to be dead. Well, at least something was able to travel to the future!
But, how about to travel to the past?

The next time, I will tell you.

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