splittingheirs t1_jedcqva wrote on March 31, 2023 at 4:47 AM

Reply to comment by GsTSaien in ELi5 If the universe is expanding, what is it expanding into? by cashmoneyhash

Space is something. It is not made of "nothing". The emptiest space is still buzzing with matter and energy.

Also quite a few physicists suspect space and time are an emergent property that reflect quantum scale interactions and relationships between matter. IE, space literally manifests itself as an illusion of quantum interactions. So if space exists, it's for the express purpose of displaying the result of material interactions that define it, it couldn't be empty if it tried.

For further information: lookup quantum loop gravity.

GsTSaien t1_jedcw78 wrote on March 31, 2023 at 4:48 AM

Is the emptiest space still full of matter? That doesn't sound right, could you elaborate?

Also, if it is emergent then it would indeed be "nothing" by itself, only existing when occupied.

How does spacetime as an emergent property explain gravity?

splittingheirs t1_jede87t wrote on March 31, 2023 at 5:02 AM

I don't mean full, as in packed full to the brim. It is teeming with energy and virtual particles. There is no space that doesn't have energy and particles. It is a property of space itself.

Also yes, you could say space is nothing because it is an emergent phenomenon. But that is besides the point as pretty much everything in physics and therefore reality are emergent phenomena of more fundamental laws and properties. IE QFT pretty much says that no particles exist and its just all waves.

If you can properly explain gravity, step up and claim your noble prize. It is one of the most hotly studied areas currently in physics. Quantum loop gravity is a theory attempting to explain gravity at the quantum level by stating that spacetime emerges from quantum interactions.