robross
Established Member

Are you familiar with the analogy of the inflating balloon as a model for expanding space?

Here's another thought experiment to consider. You probably have seen magnets in action; two opposite poles attract each other.

Think about putting two magnets on a rubber sheet, just far enough apart so they are barely moving towards each other. Then stretch the rubber sheet so the space between the magnets grows. In the "real" world this would be a very difficult experiment to perform because either the magnets are too far apart to overcome friction, or as soon as they are just a bit too close they snap together. But in between would be a state where they are just attracting each other enough to overcome the force of friction from the rubber sheet. If you left them alone, they would eventually snap together. But if you stretched the rubber sheet with the same displacement/speed as the magnets' attractive force, they would seem to sit there without moving, i.e., their relative distance would not change, even though the surface area of the rubber sheet is growing around the magnets as you stretch it.

This is one way of thinking about how local gravity works to keep galaxy clusters together while space all around them expands.
Sir, I wish to invite you to read my blog related to that, how to view a five-dimensional balloon in which its surface is a four-dimensional space-time. Maybe, It will give you an insight. Pls. check it on my personal profile, Thank you very much. Sirjon

Thanks Andrew! My how the post counts fly when you're having fun!

Well done on getting to 100 posts, I foresee you will be in the four-figure club soon. Clear skies, Andy