The space by itself however definitely has energy. There are two theoretical concepts to talk about. The first one is vacuum energy described by quantum physics. Due to uncertainty principle, vacuum energy simply cannot be zero. Even more interesting, an energy of any finite volume of vacuum has to be infinite. We can think of vacuum being a constant factory of spontaneously created and then annihilated pairs of particles and antiparticles. And that happens by virtue of it being space, not due to anything in said space.
The second concept to talk about is a cosmological constant in general relativity theory. It can be thought of as an energy density of an empty space. It is one of the candidate for the dark matter phenomenon, the fact that the expansion of the universe is accelerating.
Due to both things describing an energy of an empty space, there is an idea that those to concept has to be related.
zolotuchien t1_jee6372 wrote
Reply to comment by GsTSaien in ELi5 If the universe is expanding, what is it expanding into? by cashmoneyhash
The space by itself however definitely has energy. There are two theoretical concepts to talk about. The first one is vacuum energy described by quantum physics. Due to uncertainty principle, vacuum energy simply cannot be zero. Even more interesting, an energy of any finite volume of vacuum has to be infinite. We can think of vacuum being a constant factory of spontaneously created and then annihilated pairs of particles and antiparticles. And that happens by virtue of it being space, not due to anything in said space.
The second concept to talk about is a cosmological constant in general relativity theory. It can be thought of as an energy density of an empty space. It is one of the candidate for the dark matter phenomenon, the fact that the expansion of the universe is accelerating.
Due to both things describing an energy of an empty space, there is an idea that those to concept has to be related.