Cool Aside #1: Einstein's Theory of Special Relativity

So I decided to take a post to go into a little more detail about Relativity.

A few things that are good to know:

There are two branches of Relativity. One is Special Relativity, the other is General Relativity (often called "GR"). Special Relativity deals mostly with the effect of travelling at really high speeds (like close to that of light), while GR deals with the warping of space-time by massive objects ("massive" does not necessarily mean big. It just means "having mass").

I should make something very clear: GR is beyond my current level. While I understand some of the really cool basics, and some of the implications that it has; I do not pretend to understand it well enough to write about it.

Alright, so onto Special Relativity.

First, let's imagine you're in a car and you're travelling in some North-North-West direction and you're going at 100 km/h. In fact, let's say that your car can only travel at 100 km/h, no more and no less. Now, I only want to know how quickly you're moving West; I don't care how quickly you're moving North. I'm going to do a little bit of trig to figure out how much of your NNW speed is carrying you purely West.

Now, if we look at these arrows and say that the Green arrow shows how fast you're moving and in what direction. The Blue arrow, then, shows how fast you're moving West and the Red arrow North. We call the Blue and Red arrows "components" of the Green arrow. The West component, and the North component. If we turn the Green arrow to point more upwards then the Red arrow will become longer and the Blue arrow shorter. Whereas if you turn your car more westwards, then the Blue will become longer and the Red shorter.

"Okay okay! Where are you going with this?!"

Well, have you ever heard that if you travel at the speed of light time stops? Well it's kind of true. Imagine that North represents the speed of our passage through time and West represents the speed of our movement through space (i.e. when you walk in one direction or another). One of Einstein's theories was that our total speed (over space and time) is ALWAYS the speed of light. The idea is that the Green arrow (which for us is going the speed of light) is pointing almost entirely in the Time direction. But if we move fast enough in a spaceship then we will pull the Green arrow down towards the space direction. This causes the Red arrow to get shorter. Remember the Red arrow represents how quickly we pass through time! So if the Red arrow gets shorter then we move through time more slowly!! And if we move through space at a speed close to the speed of light, then the Green arrow points almost completely in the "Space" direction. So the faster you fly, the slower time goes by for you. This is absolutely true, but you cannot experience the effects of it unless you travel at incredibly high speeds (much much faster than planes or bullet trains).

Isn't that cool?!?! As a result of this there is something called The Twin Paradox.

The idea behind the twin paradox is that if two twins, Bob and Deb, walked together to NASA and Deb got into a rocket and took off into space. Depending on how fast the spacecraft moved, when she got back, say, 15 years later, her twin brother Bob would be much older than her!! Because she is moving so quickly in the space dimension that there's not as much total speed left over for the time dimension, so she would age more slowly than Bob!

This isn't a cool thing potheads talk about while playing hackie-sack. This is a legitimate postulate of Einstein's, one of the greatest minds of the past several hundred years (some say the greatest).

This effect is known as Time Dilation. There is also something called Length Contraction, which I referred briefly to in my last post. The explanation for Length Contraction is quite a bit lengthier (heh heh) and more of a brain buster. If you want a "Cool Aside #2" about Length Contraction, let me know.

Well, this has been fun!

Thanks for reading!