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 John Michael Godier for a guest in a Cosmology episode?

@CodysLab I'd honestly love to see that, you're very good at explaining things. This thread is a good explanation, I never really understood, but now I do.

@CodysLab So, what you are speaking about is like the rubber mat theory, objects that have gravity bend the "space" into ever more contracting circles, and the further away, the bigger those circles become? (I'll see of I can find the 2d image of what i speak of)

@CodysLab I would love a video on this! Just thinking about photons going through space that is expanding or compressing is fascinating

@CodysLab Make a cosmology podcast and have Michio Kaku and NDT on it. And Greene.

@CodysLab Absolutely! This would be a great video and I would love to show it to my kids.

@CodysLab Keep thinking this way

@CodysLab Cosmology with Cody? Absolutely! What else do you know, let me get as much as youtube will let you!!!

@CodysLab Absolutely! I loved the one where you went across the country to show (as analogy) how vast astronomical distances actually are!

@CodysLab Yes. Definitely.

@CodysLab Energy is rest. Photons do not exist in such a way as to have physical properties. Waves propagate and diffuse. Simple as

@CodysLab I'd LOVE a cosmology with Cody series. Maybe also some space for "weird" ideas like the one about photons going slower than the speed of light and stuff like that would be nice.

@CodysLab I would love to see a series of the practical applications of the Einstein Field Equations.

@CodysLab You're a good science communicator. I think there is a need for people to be "smarter" - some folks imagine aliens because we can't figure out how ancients built pyramids. Specific science topics might be a good doorway to teach a more fundamental thing - logical thinking.

@CodysLab Love to see the "serie".

@CodysLab I actually would love it, while it might be net perfect explanations, I find it's still incredibly valuable to show and explain such things

@CodysLab why does space expanding/contracting take away/confer energy? I was with you until that point 😭

@CodysLab I would very much appreciate a cosmology with Cody video or even a series! I've always been a big fan of your space videos (especially fertilizer from meteors, I still think about it and apply it to my everyday life) and I would love to see another topic you are passionate about!

@CodysLab How much do you want to bet you'll have at least one person complaining because they didn't know cosmology and cosmetology aren't the same thing? 😭😂

@CodysLab well is this the same concept as orbital mechanics?