Relativity made easy?!? WIGGITY WHAA?

If I told the average person on the street that relativity--as in Einstein's general theory of relativity--was fairly easy to understand, I'd either get a) punched for my arrogant presumptuousness or b) stared at like I was crazy. I have in fact said this to friends before, and thankfully received the latter response instead of the former.

The truth is while the mathematics of general relativity might be beyond most of us, the fundamental concepts are not. And as for special relativity, the math is something a high schooler who has mastered algebra and geometry could handle. Imagine my surprise when after calculus-ridden angular momentum, easily the most mathematically challenging aspect of my physics class, we went to special relativity--and basic algebra.

The difficulty of relativity lies in letting go of common sense. Our brains' common sense perception of the world is evolutionarily useful, but not very good when it comes to physics. For example, my common sense right now tells me that I'm sitting still at my computer, typing against solid keys. Physics tells me I am hurtling through the galaxy at bone-crushing speeds, the only force attaching me to the earth is invisible, and the keys I'm tapping on--and most of everything around me--is empty space. My mind, she is boggled. BOGGLED I SAY.

Here are a couple of the general elements of "common sense" that need to be thrown out the window before one can think clearly about relativity.

1) Absolute frame of reference. This one's pretty easy to chuck, even with Newtonian mechanics. If you're standing still on a platform and someone passes by on a train going 50 miles per hour, you perceive the person on the train moving with you standing still. They perceive themselves standing still, and you zipping by.

2) Instantaneous light. You have to think of light as something that has a finite speed--just a really fast finite speed. It's difficult since when we see a light turn on, it's instantaneous. But as a way to disabuse yourself of this notion, watch live news when the correspondent is half a world away from the anchor. There should be a slight delay in their responses to each other. That's not lag--it's because comm signals travel at the speed of light, and the time it takes the signal to get from one to another is actually perceptible to us.

3) Gravity as falling. Gravity is much more than just the force that glues us to the earth. A broader conception of gravity helps enormously with understanding relativity.

4) Absolute time. This misconception is harder to remove. A crude but effective analogy is to think of time zones. The 3:00 PM of a person living in Madagascar is not the same 3:00PM as a person living in Beijing. Now take that concept and apply it not only to hours on the clock, but also to units of time. Your one second is not the same as my one second.

Disabusing oneself of these "common sense" notions of the world is essential to understanding relativity.