Name: David M.
It is my understanding scientists think that the red
shift is due to the stretching of space or the expansion of the universe.
Is this stretching caused by anything? Does it take energy of some kind
to accomplish this? If so, where is the energy coming from?
The red shift is not due to the stretching of space or the expansion of
the universe directly. Rather it is due to the Doppler shift, which says
that the wavelength of any source of the wave increases as the source
recedes and decreases as the distance of the source becomes closer. This is
a common phenomenon of all waves, acoustic and electromagnetic, and does not
require any energy input to accomplish this.
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Update: June 2012