Is the Universe Really Expanding or Are We Just Moving Faster?

AI Thread Summary
The discussion centers on the concept of the universe's expansion versus the idea that galaxies might be moving at different speeds in the same direction. One participant suggests that if our galaxy is moving faster than distant galaxies, it could create the illusion of expansion. However, others argue that General Relativity and Hubble's Law provide strong evidence for actual expansion, as distant galaxies consistently show redshift indicating they are moving away. The uniformity of this expansion in all directions further supports the prevailing theory. Overall, the conversation highlights the importance of established scientific principles in understanding cosmic phenomena.
Tyah
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Why assume that the universe is expanding by observing that the space between our galaxy and distant galaxies is expanding. For example, what if our galaxy and distant galaxies are moving in the same direction, but our galaxy is moving faster than the distant galaxies we have observed. Resulting in the distance between to grow.

I have been thinking about this for some time. Please reply.
 
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Okay. According to this theory, in one direction, we'll be, um, moving faster (I suggest you look into a layman's understanding of Special Relativity to understand why this has no meaning :wink: ), and the galaxies will appear to be moving away from us.

But in the other direction, according to your theory, shouldn't galaxies be slowly moving towards us on average?

General Relativity alone is enough evidence for the expansion of the Universe, the observation that faraway galaxies are moving away from us just supports the theory.
 
Tyah, welcome to the forum!

Like Whovian said, the expansion is uniform in all directions. This was discovered by Edwin Hubble, using the redshift of light from distant galaxies. When he took a measure of the redshift of this light, he discovered Hubble's Law - that there is a linear relationship between the distance to a galaxy, and the redshift of its light. This is implies that space is expanding - distant photons traverse larger amounts of expanding space.
 
thank you. Your replies have been very helpful
 

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