Colliding galaxies in expanding universe

I recently came across a discussion on the expansion of the universe (click here to read the discussion). Have you tried to reason out how galaxies collide in a universe in which we know that objects are moving further away from each other at a rate that is directly proportional to the distance between them ?

#Physics

Easy Math Editor

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Comments

The expansion of the universe is something which you observe at super-cluster scale. You don't observe expansion at the level of galaxies. Galaxies are bound systems. A few ten to hundred galaxies form a cluster. They are bound gravitationally and they have their own motion. So collision can occur between galaxies. What moves with a velocity/rate proportional to distance are the clusters/super-clusters and not galaxies. Galaxies don't move with the hubble flow.

Balaji Dodda - 7 years, 6 months ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$