They say the universe is expanding. They also say it all came from a single place/state. So if everything is expanding in all different directions, wouldn’t we observe some galaxies actually moving towards us as well? It just seems like if everything is expanding away from us (nothing coming towards us), then that is assuming that Earth is the center of the universe (which is wrong obviously).
In: Physics
There are galaxies moving towards us, because the Universe isn’t completely uniformly filled with galaxies.
However, if the Universe were uniformly distributed with galaxies, which is mostly true, they would all be moving away from each other. The space itself is expanding, which makes the space between any two galaxies increasing. For a distant galaxy A, we are moving away quickly, and galaxy B near us is also moving away from that distant galaxy as well. But if galaxy B is is nearer to A that we are, then it’s moving away from A more slowly so that the distance to us and A is both increasing, from B’s perspective.
But Earth is the center of the universe. And so is the rest of the universe. The universe is expanding. So it used to be much smaller. In fact it used to be very small. Infinatly small in fact. So everything was at the center. And even though the universe is expanding everything is still at the center. The universe is just expanding in all directions. We are moving away from the far away galaxies the same way they are moving away from us.
Say you have a piece of paper. This is the universe 10 billion years ago. You put 2 dots, roughly a centimeter from each other. These are 2 galaxies.
Now imagine someone takes that same paper, our universe, and makes it 10x the size it was. This is to simulate how the universe has grown 10x in size in 10 billion years. Now if you find those 2 dots, the distance between them now should be about 10cm.
This simulates the large distance that has grown between the 2 galaxies in the span of 10 billion years as the universe itself grows.
Hope that made sense
The analogy usually used is if you put a little air in a balloon and then draw some dots all over it, and then blow it up, all the dots move away from each other. No matter which dot you pick all the others are moving away from it as you blow up the balloon and it expands. Our galaxy is like one of those dots.
They aren’t. The Andromeda galaxy is moving towards us and is expected to collide with the Milky Way galaxy in 4.5 billion years.
This is true for any place in the universe. [This video by Vsauce](https://youtu.be/3pAnRKD4raY) has a very useful visualisation of how that works (at timestamp 9:00).
> They also say it all came from a single place/state.
That is where you are mistaken. It came from a singularity where everything was very close together, but it was also the case that every**where** was close together. All possible locations were near to each other.
Now on the large scale everything is moving away from everything else simultaneously because all locations are becoming more distant.
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