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Comment by eitau_1 | Hacker News Reader

Does anyone know if JWST has seen stuff far enough for this effect to kick in?

[Angular Diameter Turnaround](https://xkcd.com/2622/)

I think about that one a lot. It goes all the way back to the CMB, which is so "big" that it is literally everywhere you look and the shapes we see were apparently at the quantum scale.

>the shapes we see were apparently at the quantum scale

I thought that was sound waves?

https://duckduckgo.com/?q=baryon+acoustic+oscillations&t=ffa...

...unless you are thinking about something else?

I don't really know, to be honest. Everything I know about it is from pop-sci sources.

According to current theory AIUI, cosmic inflation greatly influenced the CMB. It ended approximately 10^-32 seconds after the Big Bang:

"Cosmic inflation is believed to have occurred in an incredibly brief, rapid, and exponential expansion phase lasting from approximately 10^-37 to 10^-32 seconds after the Big Bang. During this minute interval, the universe expanded by a factor of at least 10^26, and potentially as much as 10^50."

Quite a theory, cosmic inflation...

Yes, as per Wikipedia that happens much closer to us, at redshift 1.5: https://en.wikipedia.org/wiki/Angular_diameter_distance

(Note: the reason to measure in red shift rather than light years is that when this comes up it suddenly gets very important to be very careful about what exactly you even mean by "how far away is that thing?")

Incredible!

So if I understand this correctly, the galaxy above in the paper is at Z=14.4 and that means it appears in the sky about as big as if it were a very small Z or roughly 350 megaparsecs away?

Yes, JWST can see as far back as 300 million years after the big bang.

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