Is The Universe Really Expanding?
This seems too simple. I must be missing something. But the following thought occurred to me, and… well, just read it for yourself.
The basis for the hypothesis that the Universe is not only expanding, but it is also accelerating, concerns the Doppler Shift. You probably know what that is. If so, you can skip the following info-dump.
The Doppler Shift is an effect caused by the length of a wave (whether a sound wave or a light wave) in relation to its motion toward or away from an observer. Sound waves emitted from something moving toward an observer will compress and the sound will pitch higher. Moving away from the observer, a sound wave will lengthen and pitch lower.
In this way, a light wave emitted from a body moving toward an observer will compress and shift toward blue. If moving away, the wave will lengthen and shift toward red. How red or blue the light appears results from the velocity the object is moving. The faster the object moves away from observer the redder. The faster the object moves toward the observer the bluer.
-End of info-dump.
However, I have to ask how proponents of this hypothesis are taking into account the finite speed of light? As, the greater the distance an object is from an observer, the farther in the past it will be perceived in relation to an observer.
Therefore, when you consider the speed of light with the Doppler Shift, isn’t the question confounded? In other words, the farther away a galaxy is, the faster it appears to be moving. However, it is also true that the farther away a galaxy is, the more it will be observed as it was in the past.
To sum up. A galaxy moving away from an observer is red shifted; but it also appears as it was the past. Thus, “Galaxy X” may appear to be moving faster, but in the distant past. And might the Universe not be expanding at all, and possibly even be contracting? I think Tom Petty said it best: “I Need To Know”.