So all space is expanding. Locally, that’s “just a teeny tiny bit,” and the force of gravity is plenty strong enough to keep things up to about the size of galaxies (maybe galaxy clusters) gravitationally bound. Andromeda, for example, is the only galaxy that is heading towards us.
But all of space is quite big. Over the vast distances of space, all of the “teeny tiny” local expansions add up. This means that the galaxies which are furthest away from us are also receding from us most quickly. This is not because those galaxies are moving through space; it’s because of all the expanding space in between them and us.
The speed of light (in a vacuum) is the fastest anything can move through space.
Consider a balloon. Uninflated, make a mark on opposite sides, and then make a third mark right next to one of those. When you inflate that balloon, the two points on opposite sides of it become farther apart because of the stretching of the whole balloon, but the two marks right next to each other don’t become nearly as far apart, because they are only experiencing “local” expansion.
So all space is expanding. Locally, that’s “just a teeny tiny bit,” and the force of gravity is plenty strong enough to keep things up to about the size of galaxies (maybe galaxy clusters) gravitationally bound. Andromeda, for example, is the only galaxy that is heading towards us.
But all of space is quite big. Over the vast distances of space, all of the “teeny tiny” local expansions add up. This means that the galaxies which are furthest away from us are also receding from us most quickly. This is not because those galaxies are moving through space; it’s because of all the expanding space in between them and us.
The speed of light (in a vacuum) is the fastest anything can move through space.
Would a fair, albeit crude, analogy be like when I fart and the gas forces my butt cheeks apart (the expansion between two objects)? (_|_)💨
Crude, yes. Fair, no.
Consider a balloon. Uninflated, make a mark on opposite sides, and then make a third mark right next to one of those. When you inflate that balloon, the two points on opposite sides of it become farther apart because of the stretching of the whole balloon, but the two marks right next to each other don’t become nearly as far apart, because they are only experiencing “local” expansion.
I wanted to make a fart joke.
But I like your balloon explanation. That makes sense to me.
We must sometimes succumb to our basest instincts.
Don’t you mean our basic stinks?
Ok I’ll stop.
Fill the balloon with a fart
Just fill the balloon with farts.