What Actually Expands In An Expanding Universe?

As the universe expands, #expanding #space is said to "stretch" photons. But if it stretches photons, does it also stretch molecules, galaxies and you? A portion of this video was sponsored by Salesforce. Go to https://salesforce.com/veritasium to learn more. Special thanks to Geraint Lewis - this video was based on his paper "On the relativity of redshifts" https://arxiv.org/abs/1605.08634 Check out his YouTube channel: https://ve42.co/gfl and books: https://ve42.co/GFLbooks References: Expanding Space: the Root of all Evil? Matthew J. Francis, Luke A. Barnes, J. Berian James, Geraint F. Lewis https://arxiv.org/abs/0707.0380 Editing and VFX by Trenton Oliver Thumbnail by Ignat Berbeci Music from https://epidemicsound.com #SMB #smallbiz #startups #SalesforceEssentials