Expansion of Space
Name: Carl W. R.
what is meant by 'the expansion of space'? Since space is
empty, how does it expand?
Touche, Carl, many concepts are truly meaningless if the space is truly empty. But it never is completely empty.
Space is said to expand when the locations of objects sitting in that space get farther apart,
more than they would have just by coasting around with known velocities and forces.
One may compare with the size of the objects themselves, which may be holding themselves together with a constant size.
Planets, stars, and probably galaxies do this.
So maybe space is the same, but there is an unknown force out there, pushing galaxies away from each other?
Always a possibility.
Light waves have been out there, in all parts of the space around us, from seconds ago to billions of years ago.
We have figured out what made most of it, piece by piece, color by color.
When space expands, the light waves in that space are stretched out, changed from blue to red,
from red to invisible infra-red, from infra-red to radio waves.
We notice this happening, so we are inclined to say that space expanded,
because most forces do not have any effect on light waves in flight.
Gravity affects light waves, but gravity is closely related to the shape of space itself, in all current theories.
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Update: June 2012