Friday, April 21, 2017

Relativity: The Light's Side Of The Story

When we look at pole star, it draws awe about the fact that the light from pole star took a span of 433.8 light years to reach us.  It seems so ancient. Our lifespans seem quite insignificant compared to the vastness of the universe.


I like to think about what earth was like when the light that I see tonight left its place of origin. For the pole star, It was roughly when Columbus discovered America. It is nice to see things from different perspective. For this post, I have decided to think about the journey of a photon that I see tonight when I look at the pole star. Our earth-bound instinctive thinking may say 433.8 light years that must has been an awful long boring journey. Actually, it was not long for the photon. In fact, it was instantaneous. Because, Drumroll Please, Relativity! Let me explain.

We often hear the speed of light is always, well! The speed of light! that equals to 3 X10^8 meters per second. At this point, I am holding in my urges to mock America for its choice of units. Now imagine you are riding a bike in space, going with the speed of light. It's a hypothetical space bike and you are wearing a spacesuit ... Blah blah blah, you are safe.  Since space is dark, you have the headlight on. So the light leaving your bike is the same speed of your bike. Instinctively it shouldn't leave at all. However, that is not how the universe works. The beam of light leaving your bike will still be traveling away from you at 3 X 10^8 meters per second. No matter what reference frame we are considering the speed of light will always be the same.



 Now if light's speed remains constant how does it work! Speed is the distance traveled (length) per unit time. If speed remains constant then the variation lies in length and time. Einstein, in his theory of relativity, explains how the time, mass and length vary with speed. He used Lorentz transformation to work out the relation and find out the relative change in mass, length and time. I would spare you the mathematical side of this, still, if you are interested you may check out the details of Lorentz transformation here. Now, long story short, when an object approaches the speed of light its mass increases, time dilates and length contracts with respect to the objects at rest. 

The more the speed approaches equals to the speed of light the time slows down. At the speed of light time stands still. If it were to go beyond the speed of light (hypothetically) the direction of time will flip and move backward. That will break the law of causality. The law that governs that cause should be followed by effect. So the speed of light is the speed of causality


Another thing that changes with speed approaching the speed of light is mass. We know that inertia increases with speed thus mass also increases.  In a way, the mass is the speed restriction; anything having mass cannot reach the speed of light. The closer the speed reaches the speed of light heavier the mass becomes. 

So if you were really aspiring to ride that bike with speed of light, I am sorry to burst your bubble. You would have an infinite mass and will require infinite energy.  We don't really have that kind of energy! Actually, we don't know how much energy we have in the universe or if it is finite or not. We don't even know if the universe is finite or not. 



In the case of light, photons, it is a massless particle. For the photon, traveling with of light from the pole star to us, time stands still. From the point of view of the photon, that journey would have occurred instantly. It took 433.8 light years from our perspective only. Same is true for the first ray of sunlight that takes eight minutes to reach us from the surface of the Sun. However, for that light ray, it leaves the sun's surface and reaches us in no time. 

The constants, such as speed of light, in the universe that governs the laws of it are a set of certain values that makes the universe possible. Had there been a slight variation in the value of any of these universal constants I wouldn’t be here writing this post nor you would have been here reading it. We wouldn’t exist. Isn’t it wonderful that light travels with 3 X 10^8 Meters per second and we do exist (Or do we?)
Feel free to contribute your thought and opinions in the comment section


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10 comments:

  1. That got a little more scientific but I know what you mean. Isn't that what Einstein said about the theory of relativity.

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  2. This is just a gist the Einstein's theory of relativity itself! Don't be afraid I have kept it very simple for #AtoZChallenge. Despite my desire to add more hardcore stuff to it, I am keeping this soft.
    Thanks for stopping by :)

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  3. Nothing wrong with going hardcore, as long as you include some easy stuff for those who haven't had a science class since high school.

    I love including links to hardcore stuff for those who want a challenge.

    Her Grace, Heidi from Romance Spinners

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    1. I agree! I love your posts hardcore stuff.
      Thanks for stopping by. :)

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  4. That's a fun post. You turned to the perspective of photon. That is quite different. The outcome is just bewildering.
    well done (Y)

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  5. Just catching up on stuff now ... a very thorough synopsis though, despite not getting too hard core. I was never much for science when I was younger, but now I wish I had paid more attention.

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    1. Thanks! Glad to see you stop by. :)

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  6. Great way to to bring a sometimes confusing concept into a new "light!" Sometimes simplifying science is exactly what we need to do to get others interested. Then, beef up the content when they're ready!

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    1. Indeed, that one counter-intuitive thought rise curiosity. Then the questions leads the seeker to the answers. :)
      Thanks for stopping by.

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