What Actually Expands In An Expanding Universe?

Special thanks to Geraint Lewis - this video was based on his paper "On the relativity of redshifts"

References:
Expanding Space: the Root of all Evil?
Matthew J. Francis, Luke A. Barnes, J. Berian James, Geraint F. Lewis

Editing and VFX by Trenton Oliver
Thumbnail by Ignat Berbeci

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[DEADPOOL-]

Don't know if it's universe, but I expanded a LOT in this quarantine

[cyto]

Bucket list after corona times:
1. Going in outer space
2. Turning off Electromagnetic force

[variation]

"You might think there's only one type of redshift. But in fact, there's three. But actually, there's one."

[GrimGearheart]

I appreciate you, dearly. I've recently been going through old videos of people like Feynman and Sagan. They existed at a time when video technology was still...amorphous. We only have so much video of them, and they died so long ago. I know they would be proud of creators and educators like you who are carrying on their work. Thank you.

[abhishekthorat]

I'm happy that Derek is now uploading frequently.

[shubhamgupta]

Me personally holding a degree of Masters in Physics, still this guy, with every video, brings out the attention to something which seemed to me very trivial in the first go but never gave a second thought, and blows my mind every single time. I don't know how Derek does it. Best youtube channel I've ever subscribed to.

[rwester]

As an addition to explain the difference in observation, to greatly simplify. The redshift in light kind of works the same for sounds. When you hear the siren of an ambulance it sounds different when the ambulance is driving towards then when the ambulance is drives away from you. thats why you know it is moving towards you or away even if you don't see it. But the sound the ambulance makes is always the same, just perceived different

[fattahpras]

I swear the title changed from "are you expanding with the universe" to " what actually expands in an expansing universe" and i think the thumbnail changed too. It's refreshing watching old veritasium videos. This video is actually one of my favorite veritasium's video, i think i watched this video at least 6 times

[sambhavbhalla]

Consistent uploads with quality wow how's that even possible

[GDIBass]

This whole "you're currently accelerating because of gravity" thing is still kind of making my head explode.

Also, you're killing it.

[JoeWhiley]

No other content creator has the ability this guy has to be able to explain concepts to 14 year old me and then 6 years later help me understand another concept the day before a final year Undergrad Physics exam...different level

[FabulousJewishKitty]

very interesting and thought provoking, makes me want to go learn physics to fully understand what I fully imagined just now.

[Jacob-yglz]

"Why's it red?"

"Because spacetime is expanding between us at an accelerating rate"

[raoulherbord]

Oh man I have been wondering about this question for as long as I know everything expands

[ronasor]

ive seen 2 explanations before this one, and this one is by far the clearest, most well-suited for the average joe to understand. thank you.

[rouelandrewpulma]

"Are you expanding with the universe?". *Looks at belly*. "Why yes, yes I am"

[fendoroid]

Me when electromagnetic force disappear: Mr. Stark, I don't feel so good

[leopoldohortaleza]

In the difficult time of Corona, I am glad Derek provides us with videos more frequently. Life has become stagnant for me, and I feel like i'm getting dumber since there's so less to do and learn from during this time. These videos are a breath of relief for me and I really appreciate it. Thanks, Derek.

[BrunnoOliveira]

I want tô thank all of you that work on this channel for explaining that question. The first time I heard about the expansion of the universe I wondered about us being expanded as well. I could't find the explanation for this anywhere until I seen this video. That question literally gave me insomnia in the day I thought about It, now I can sleep 😅

[BryanLawlor]

Someone needs to build a really good special relativity simulator to show the visceral look and feel of these spacetime transformations. I want to see how a ship's appearance would change as it passes by at semi-luminal speeds. I want to see how the colors would shift, lengths would contract, and time would slow down from each observer's perspective. Could you get on that?