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\f0\fs28 \cf0 Imagine learning for the first eighteen years of your life that the earth

is flat. All through elementary school and high school you grow up hearing about the

flat earth we live on and doing boring flat-earth physics homework and then (if you're lucky

enough) you get to college and PSYCH! \f1 for the first time they show you a globe

and say "sorry for lying, the earth is actually round".\

\ Well, this is, unfortunately, exactly what

we do with\ \

1) Gravity\ You probably learned that objects attract

each other based on their mass so you probably grew up thinking that light can't possibly

be affected by gravity because light is massless. I know I did. Well guess what? The source

of gravity is not mass - it's energy and momentum, which light certainly has (of course, regular

matter does too). So not only does light get bent passing by a star or planet or black

hole, but light attracts the planet or star or black hole in return (to be sure, it's

only a very very small amount. But a small amount is not zero). Anyway, the point is

that Newton's law of gravitation is just an approximation - good enough to get us to the

moon, but not perfect. General relativity is better.\

\ 2) Special Relativity\

Speaking of the moon, you probably also learned that if a sheep is moving 2 mph relative to

a train and that train is moving 2 mph in the same direction relative to the ground,

then the sheep is moving four mph relative to the ground. 2mph+2mph=4mph, right? FALSE.

Experiments in special relativity have confirmed that velocities don't simply add together

and so the sheep will in fact be moving very very ever-so-slightly slower than four mph

relative to the ground. And the formula that correctly predicts this deviation from just

adding the velocities is (v1+v2)/(1+v1*v2/c^2). It's not a very big effect, but then again,

the earth looks pretty flat, doesn't it?\ \

But the earth isn't flat: if I walk 10,000km away from my cat, and you continue on walking

10,000km more, you're NOT 20,000km away from my cat. You're just 12,750km away\'85 in fact,

the farthest on earth you can get from ANYTHING on earth is 12,750km. It's the "earthly distance-limit",

though we normally call it the diameter of the earth. And similarly, when you try to

add two velocities together, there's a "cosmic speed limit" of 300,000,000m/s - that is,

the speed of light.\ \

So, just because to our eyes the earth looks flat, velocities look like they simply add

together, and light looks like it doesn't attract gravitationally, is that an excuse

to mislead ourselves and our children about the true nature of things?}