Time Dilation

If I had not pursued a career in medicine, or if I had not discovered my love for economics and investing, then I would have definitely become a physicist.  Specifically, I would love to study astrophysics related to general and special relativity.  I was reading about time dilation today, and it absolutely fascinates me.  In classical physics space and time are independent.  Furthermore, time is a constant.  No one would argue that you can change the length of a second.  If you could slow down or speed up time, this would change our view of the way the universe operates.  Well, according to relativistic physics, time and space are merely dimensions of the same variable. 

This concept is conceptually complex because it has been engrained in our minds that time is constant.  And it might as well be if you are not traveling at speeds close to the speed of light.  However, as you approach the speed of light, time actually slows down.  This has been shown experimentally time and time again with atomic clocks and the changing half-life of muons traveling near the speed of light at CERN compared to stationary muons.  Gravity, or warped spacetime due to mass, also affects the rate of time.  With less gravity time travels faster while more gravity slows down time.  Modern GPS systems must account for different rates of time because satellites have a lower force of gravity affecting them compared to devices on Earth.  Therefore, they are operating in different relative frames of reference.  This effect is referred to as time dilation.  The change in time between atomic clocks in these examples is on the scale of nanoseconds, so it is something that we would never notice. 

That all sounds very nerdly, I know.  But if one were to apply it to near light speed travel, you get much bigger changes.  Imagine if we had the technology to travel 80% of the speed of light.  If a spaceship were to travel to a solar system 4 light years away, then it would take about 10 years to travel there and back according to time on Earth.  The amount of time traveled by the spaceship is reduced by the reciprocal of the Lorentz Factor.  In this case it happens to be 0.6.  So it would take 0.6x the time it did on Earth.  The spaceship would travel there and back in 6 years.  The people on Earth would have aged 10 years, and the people traveling 80% of the speed of light would have only aged 6 years.  This is only 6 years relative to the 10 years experienced in the frame of reference on Earth.  Because time is variable it has to be a relative comparison.  I am not sure if this is why the theories are called relativity or not, but it I will definitely have to look into that. 

You can take this idea even further.  Suppose the technology existed, again, and that there was a spaceship capable of traveling 99.9999% of the speed of light.  The reciprocal Lorentz Factor would be 0.045.  This means that if the spaceship were to travel space at 99.9999% the speed of light for 22 years, then 500 years would have passed on Earth.  This is a relative way to travel into the future!  Of course, you are not actually traveling into the future, but relatively you are.  How wild would it be to return to Earth after the trip to find that several generations of people and technology had passed by?  You would be returning to a completely different planet in many senses because so many things would have changed!

This kind of theoretical thinking exercise can entertain me for hours.  The only thing that saddens me is the fact that the necessary technology will not exist in my lifetime to perform time dilation on a time scale that is noticeable.  I really do hope that one day someone figures it all out and wins a Nobel Peace Prize for their efforts. 

**I would like to point out that I am not an expert on this stuff, and this information is only what I gathered from reading scientific articles and other websites on the internet.  If you have any insight to add or questions to ask feel free to comment or email me!

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