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The James Webb Space Telescope is finding too many early galaxies

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Re: The James Webb Space Telescope is finding too many early galaxies

#21

Post by ben_w »

cwkoss wrote: post #14

Is it possible that the 'edge' of universe reflects light? Have scientists been able to conclusively rule that out somehow? Does the universe even have an edge? What is our current understanding of what the boundaries of the universe might be like?

The far limit of the visible universe is the cosmic microwave background, which is the heavily red-shifted view of when all of space was filled with an opaque plasma of similar temperature to the surface of a star[0].

The galaxies we're seeing are in front of that.

[0] 3000 K, https://en.wikipedia.org/wiki/Recombination_(cosmology)

Re: The James Webb Space Telescope is finding too many early galaxies

#22

Post by Tuna-Fish »

cevn wrote: post #4

Can someone explain to me what would be behind the galaxies if we could see it, to the point of 0 seconds after the big bang? Black, white, is it even possible?

We can't see down to 0 seconds, because very soon after the big bang, the universe was filled with dense, extremely hot, opaque plasma. The closest we can get is the "recombination epoch" [0], which is roughly 370 000 years after the big bang, when, because of universal expansion, the plasma got cold enough for neutral hydrogen to start forming, at which point the universe became transparent.

As protons gain electrons in high temperatures, they don't form in the ground state. Instead, the newly minted hydrogen atoms are in a highly exited state. As they fall back to their ground states, they emit infrared photons at ~3000K color temperature. These photons, redshifted by the expansion of the universe to ~2.7K, are the Cosmic Microwave Background, the uniform ultimate backdrop we have when looking in any direction.

[0]: Which has it's slightly incorrect name (should not have re-) because it was named before the big bang became a widely accepted or known theory.

Re: The James Webb Space Telescope is finding too many early galaxies

#23

Post by twawaaay »

cwkoss wrote: post #14

Is it possible that the 'edge' of universe reflects light? Have scientists been able to conclusively rule that out somehow? Does the universe even have an edge? What is our current understanding of what the boundaries of the universe might be like?

The edge of visible universe is Big Bang. Or more concretely, the time couple hundred thousand years after Big Bang when the universe became translucent to light.

Things cannot "reflect off of the edge of visible universe" because that would require that the light travel back in time which is nonsense.

As of this moment we cannot exclude possibility of discontinuities in the universe which would be cause for example by inflation. But we also have not observed any.

Re: The James Webb Space Telescope is finding too many early galaxies

#26

Post by oblio »

pwatsonwailes wrote: post #18
eganist wrote: post #15

Earlier quoted context omitted.

> Is it possible that the 'edge' of universe reflects light? Have scientists been able to conclusively rule that out somehow? It's not an edge the way you think. It's the edge of what we can see based on the known age of the universe and how much light has reached us. I.e no real boundaries as best as we can tell. The best way you can look at this is that early galaxies are being found earlier than expected based on…

Without getting into lots of detail, this is basically correct. It's why we talk about the observable universe. There's lots of stuff we can't see because the light from it won't reach us.

I was thinking about something weird right now.

We don't (can't?) even know if there weren't multiple Big Bangs, right?

I.e we're just in a specific "universe" we can observe, but maybe several of these are just side by side, not necessarily parallel as in parallel realities.

Re: The James Webb Space Telescope is finding too many early galaxies

#27

Post by limbicsystem »

Pxtl wrote: post #16
feoren wrote: post #12

Earlier quoted context omitted.

Not an expert here but it sounds like you might be describing the Cosmic Microwave Background. This is basically the remnant of the early opaque plasma cloud that filled the entire universe. As we look far away/back in time, the photons reaching us have redshifted due to the expansion of the universe. That's why these originally extremely high-energy photons are now just low-energy microwaves. The "background", 0 sec…

There's always a relevant xkcd for every science question, and in this case it's one of the first ones: https://xkcd.com/54/

But oddly the most recent one as well https://xkcd.com/2723

Re: The James Webb Space Telescope is finding too many early galaxies

#28

Post by ben_w »

rjrodger wrote: post #9
cevn wrote: post #4

Can someone explain to me what would be behind the galaxies if we could see it, to the point of 0 seconds after the big bang? Black, white, is it even possible?

Visible light was scattering off densely packed electrons up to about 300k years after the Big Bang - so I guess - white.

White, redshifted so hard it's the blackest black we ever experience.

(I want to add a H2G2 joke here, but I can't figure the right way to reference making God disappear in a puff of logic related to the Babelfish…)

Re: The James Webb Space Telescope is finding too many early galaxies

#29

Post by seanw444 »

Tuna-Fish wrote: post #22
cevn wrote: post #4

Can someone explain to me what would be behind the galaxies if we could see it, to the point of 0 seconds after the big bang? Black, white, is it even possible?

We can't see down to 0 seconds, because very soon after the big bang, the universe was filled with dense, extremely hot, opaque plasma. The closest we can get is the "recombination epoch" [0], which is roughly 370 000 years after the big bang, when, because of universal expansion, the plasma got cold enough for neutral hydrogen to start forming, at which point the universe became transparent. As protons gain electron…

So if we can see CMB in all directions, why do we really even say "the observable universe" as though there could be more matter and more galaxies beyond what we can see? If the maximum of what we can see is implied to be before all galaxies, then shouldn't it be implied that all galaxies that exist can be seen?

Re: The James Webb Space Telescope is finding too many early galaxies

#30

Post by SkyMarshal »

pwatsonwailes wrote: post #18
eganist wrote: post #15

Earlier quoted context omitted.

> Is it possible that the 'edge' of universe reflects light? Have scientists been able to conclusively rule that out somehow? It's not an edge the way you think. It's the edge of what we can see based on the known age of the universe and how much light has reached us. I.e no real boundaries as best as we can tell. The best way you can look at this is that early galaxies are being found earlier than expected based on…

Without getting into lots of detail, this is basically correct. It's why we talk about the observable universe. There's lots of stuff we can't see because the light from it won't reach us.

> because the light from it won't reach us.

This is one of the most interesting aspects to the universe. It's not, "because the light from it hasn't reached us yet but is on the way and will get here eventually."

Rather it's that the rate of expansion of the universe is accelerating, so that we're moving away from parts of it faster than its light can cover the distance to us. It will never reach us.

That's mindboggling.

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