eli5 If matter cannot be destroyed or created, how does space constantly expand?

Question

Maybe I’m misinformed about this. But I was always told matter cannot be destroyed or created. But I have been told space is constantly expanding. Is this expansion of space not made up of “matter”? Where does it come from?

In: 282

Answer 1

Space is not filled to the brim with matter. Space, for the most part, is just that empty space. As the universe expand, the density of the universe decreases. Eventually there will be so much expansion, the idea will be that gravity will loose out and everything falls apart.