Have you ever used those moving walkways at an airport? If so did you notice the little bit of energy needed to keep going the same speed relative to the ground as you get on? Now imagine an infinite number of them lined up.

You would feel as though you were walking normally but someone on the ground besides the track would see you accelerating and burning calories to do it. That's what happens to photons as they travel through expanding space. They lose energy, shifting frequency towards the red.

And it's not just photons, other particles: hydrogen ions, stars, bullets ect also lose energy when moving through expanding space. It's one of the main causes for the universe to cool over time. And it's why things fall to the ground when released.

Massive objects compress space so when moving away from something big like the earth space expands and that extracts energy from an object; Baseballs slow down light red-shifts ect. The reverse, moving towards the massive object, gives energy because space is contracting.

This is a hard topic to make fit in tweets. I hope it makes some sense. If not feel free to ask questions. Would you like to see me make a long form video on this? Maybe a series? "Cosmology with Cody"

@CodysLab Everyone always describes dark energy as new space being created between objects but seeing gravity described like this sounds like dark evergy is just like the space version of isostatic rebound.

@CodysLab big bang would have taken no time, since lack of mass. I cant remember the name of the Russian guy that worked this out into a math. Vesselin Petkov? Once you start thinking in 4 dimensions it sends me off the deep end.

@CodysLab Do you mean space contracts as you approach a massive object, or space is constantly contracting near massive objects? The latter seems untrue because objects aren't heated while sitting on the surface of the Earth. If the walkway pushed into a wall, it would grind up your shoes.