4 ms·
Exactly, and I saw that when the Andromeda Galaxy collides with ours, it's unlikely many planets/systems will be colliding with one another.
by mrarjen 8y ago
Exactly, and I saw that when the Andromeda Galaxy collides with ours, it's unlikely many planets/systems will be colliding with one another.
- boznz 8y agoNever really understood how galaxies can collide if space has been expanding since the big bang and everything is moving apart
- ben_w 8y agoIt goes both ways depending on distance. Expansion is exponential (ish), gravity is inverse-square [1]. Only the few that happened to be close enough that gravity is more significant than expansion can collide. [1] at least in Newtownian physics. The argument is geometry, so I suspect but am not qualified to say it isn’t exactly inverse square in GR.
- mickronome 8y agoSame reason I can collide with someone on the sidewalk while the universe is expanding at tremendous speed. Over short distances, the expansion can easily be overcome by others forces like gravity or my muscles excerting force through friction against the ground. However, given enough time, there will be less and less objects that are close enough to be able to collide at all. Lots of time though, and there are already now lots of things over galaxy could never ever collide with.
- Retric 8y agoOn very large scales gravity collected mater into what look like spider webs, with vast amounts of empty space and threads of interstellar gass which can form galaxies. Those galaxies form little clumps within those threads with gravity causing them to orbit each other. However, as it's a many body problem things are not stable over very long time frames and galaxies often hit each other. This does slow down over time as there are fewer remaining galaxies in a cluster.
- nabla9 8y agoMetric expansion of space has effect only on very large scale. Galaxy clusters have enough gravitational force to keep them together.