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Unit 7: Astrophysics Page 35
It depends on your viewpoint (or Do they go flying everywhere
frame of reference). because they are really going 600
mph, or do they act just like they
To you, you see only the speed of would if they were at rest?
the ball. To an observer standing
on the dock watching you as the
boat passes by, they see a faster
speed for the ball, because the
speed of the ball is added to the
speed of the ship. So which
perspective is right?
They both are.
And this is what makes special
relativity so ingenious! You know from experience that the
peanuts are easy to get out of the
Special relativity simply states bag – they act just as they would
that the laws of physics are as if you weren’t’ moving at all.
valid for all observers in The laws of physics are the same
uniform motion. for all observers in uniform motion.
All frames of reference (in uniform If your boat enters a storm or the
motion) are equally valid for doing plane encounters turbulence, then
physics experiments in and having the peanuts go flying everywhere,
the laws of physics hold true. the tennis ball bounces in some
odd direction, and you don’t have
What if you’re traveling at 600 uniform motion anymore. When
mph? Are the laws of physics still this happens, you need to use a
working? Can you play tennis just more complicated form of relativity
the same on a plane at 600 mph as to account for the acceleration,
you would in a boat? called General Relativity (which
we’ll get to later).
Yes, as long as the plane is moving
in a straight line at constant speed. By the way, the word ‘special’ in
Special Relativity simply means
You know this already, intuitively –
that this is a ‘special case’ in which
let me show you how: have you
the motion is uniform. There’s
ever tried to open a bag of peanuts
nothing else special about it except
on an airplane?
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