Movie 7 (:16)
Script : Moving
with the tram, the world around us shows the same distortions.
This is the Terrell effect. When generalized to an entire view
its known as relativistic aberration.
Also, when we move with the tram, it seems to move faster - time
dilation at work.
Comments : A "correction
frame" inside the green lines filters most relativistic effects
out, leaving only aberration effects to study.
Aberration of
light occurs any time the normally straight path of light is bent.
For example, aberration can occur when you set a glass of water
on a newspaper, and the black letters appear distorted.
This kind of aberration
occurs because light travels more slowly through the glass and
the water than the air. As a result, its shortest path to your
eye is "bent". And light always follows the shortest
possible path to your eye. If there were a shorter path, then
something could follow that path and exceed the speed of light
!
Note that even
in glass, nothing can exceed the speed of light, but it is INCORRECT
to say that the speed of light is constant. It's constant for
any particular stuff it's travelling through (its MEDIUM), but
light does change speeds as it moves from water to air. It bends
as a result. This acounts for the wavery look over a barbeque
: light bends as it changes speeds moving from pocket of warmer
and colder air.
Relativistic aberration
occurs as a result of the finite speed of light.
Imagine running
through a wide hallway, filled with people who will throw rotten
tomatoes at you. You can run fast, almost as fast as the tomatoes
can fly through the air.
Well, that's going
to throw off everyone's aim. If they're right alongside you, they'll
have to throw ahead of you, and if they're behind you, they'll
have to throw way ahead of you. And their aim will change if they're
near the middle of the hall, close to your path, or farther out
along the walls.
The tomatoes are
photons. "particles of light". And relativistic aberration
appears throughout this series of movies, in many different forms.
Depending on how
an object is moving relative to you, the observer, it may appear
:
a) as an apparent
"turning" of the tram (referred to as Terrell rotation,after
the person who first described it in detail), so that you can
see the rear of the tram even though it's going straight past
you
b) a curving of
objects like buildings which you expect to be straight
c) seeing the backs
of signs you've already physically passed appear out ahead of
you.
d) a gathering
of all the stars in the universe to a narrow "porthole"
in front of you
e) or even extremely
distorted continents on a globe which still appears round.
Of course, if a
simulation shows ACCELERATING, you'll see relativistic aberration
effects grow more extreme.