I heard that galaxies are receding from each other because the ‘space between them is expanding’. Does this mean the ‘fabric’ of space can swell infinitely? How? Why?
Ta
In: Physics
People talk about spacetime like it’s a physical thing you can touch, but in actuality it’s a geometric surface used in the mathematical model of general relativity. So the answer to your question is that space does not need to stretch because it isn’t a thing.
The question that follows is why do we say the universe is expanding? In GR the function for measuring distance between two objects is the [scale factor](https://en.m.wikipedia.org/wiki/Scale_factor_(cosmology)#Detail), and it includes a time component. So the distance between two very distant objects will increase with time. This lines up with real-world observations, so we say it’s expanding.
However GR does not explain how or why things work in the real world, so there’s no real answer to your question. Suffice it to say that nothing is actually stretching in the sense that you’re thinking.
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