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Originally Posted by NemesisX
Some more interesting musings about traveling at or near the speed of light.
Has everybody heard of the 'Twin Paradox'? It's not actually a paradox, but rather a thought experiment from Einstein that is proven to be accurate to the 8th (or something ridiculous like that) decimal point.
You all can watch videos on it but I'll briefly summarize the key points here:
When people travel at some velocity, their clocks tick slower than if they stand still. The effect becomes magnified the closer one reaches the speed of light.
Suppose you had twins born in the year 2000. They are both 1 day old.
Suppose Twin A goes off into a rocket ship that travels near the speed of light away from the earth and then towards the earth. From Twin A's perspective, he is in this rocket ship for 20 years. 10 years traveling away from the earth and then 10 years traveling back to earth, all at near speed of light velocities.
When Twin A returns to earth, how old is Twin A and how old is Twin B?
a) Twin A is 20 years old. Twin B is -not- 20 years old (despite the fact that they are twins!). Twin B is now 70 years old (I'm using whole numbers and did not actually do a calculation, but this is just to get the idea).
These results are derived from einstein's special theory of relativity. These numbers are taken into account for GPS satellites traveling at tens of thousands of miles per hour. If you did not take special relativity into account (the same equations that predict Twin B will be 70 years old), then GPS satellites would be off by miles within seconds to minutes of operating.
There is also a russian astronaut that's been on a Russian space station traveling at tens of thousands of miles per hour for so much of his life that he has effectively time traveled into the future by something like .05 seconds. Nothing crazy and from his perspective it's almost imperceptible, but it's cool nonetheless.
But back to aliens, if aliens were to travel at near speed of light to try and reach us, from -their- perspective they could travel 200,000 years to reach from one end of the Milky Way galaxy (their home) to the other end (our home).
However, from -our- perspective we will have aged far more than 200,000 years. We will have aged billions of years. The same problem holds true if we try and reach them via near speed of light travel.
Edit: Full disclosure I am a physician, but I do have a background in chemical engineering. Nonetheless I'm no expert on relativity so please correct me if any of this is incorrect!
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You are a physician so I'll speak to you as an educated person. What you are describing is the theory of relativity. Not the law of relativity. The reason it is called theory is that it hasn't been proven true.
In fact it's been shown to be false
Relativity works for basic concepts and some of our basic observations of the universe as we were learning about physics, as a human race. Now it's good for explaining some parts of physics at a college level. But our understanding of the topic has moved beyond that theory.
I only mention this in case you are curious about the topic. There is much more development on the subject which is very interesting, but that theory should be put aside unless you want to be a high school physics teacher