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The James Webb Space Telescope is finding too many early galaxies

skyandtelescope.org

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

#11

Post by klodolph »

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?

Correct me if I'm wrong.

Cosmic microwave background is behind the galaxies, and we can see it. The universe is mostly transparent these days, so light can travel across the universe from a distant galaxy to our eyes or telescopes. Long ago, the universe was full of ions-free electrons and protons-and these are very effective at scattering light, so the universe was effectively opaque at that point. The universe became more transparent as the universe shifted towards hydrogen atoms instead of free electrons and protons.

Whatever the universe happened to look like during that transition period, from opaque to transparent, is still what we see. It's the cosmic microwave background. Anything from before that time got absorbed.

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

#12

Post by feoren »

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?

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 seconds after the Big Bang, is in all directions, and presents as the Cosmic Microwave Background. Or so I understand.

https://en.wikipedia.org/wiki/Cosmic_microwave_background

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

#13

Post by soiler »

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 actually already see that time period, in its present form. It's called the Cosmic Microwave Background. It is the (now extremely cold) energy which permeated the entire universe in that very early time period. The entire universe was opaque and extremely hot... then as it expanded, it began to cool enough for particles and then atoms to form. Only then were stars possible, and later galaxies.

How/why can we see the CMB? Well, it was everywhere. Literally every point in the universe was a nearly uniform sea of blazing energy. So if you look far enough in any direction, you will see the cold echoes of that time period.

edit: Beat to the punch! I hope among our many answers you've found something enlightening

edit 2: Important to note that the CMB is not synonymous with the beginning of spacetime. It is more like a wall, beyond which we can't see anything, and it came down very early in time.

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

#15

Post by eganist »

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?

> 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 our model of how the universe formed. The further you look, functionally the further back in time you look (not just further away)

This is an oversimplification and an astrophysics expert can give you something better.

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

#16

Post by Pxtl »

feoren wrote: post #12
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?

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/

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

#17

Post by soiler »

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?

What is the edge of the universe? How would you define that? In most models, the universe doesn't have anything that could be called an edge. Unless you are referring to the boundary of the local universe, which is defined as the sphere around us at which objects are too far away for their light to ever reach us. It's not a physical structure that could reflect light, it's more like the opposite of that.

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

#18

Post by pwatsonwailes »

eganist wrote: post #15
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?

> 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.

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

#19

Post by teraflop »

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?

No, we have no evidence that the universe has any kind of "edge" that is topologically different from its interior.

There is a boundary to what we can see. As the early universe cooled, it changed from an opaque plasma to transparent gas. So as we look farther away, and also backward in time, we see the last point at which it was opaque; this is the cosmic microwave background. But this isn't a "real" boundary that something could hit. And it long predates the formation of galaxies, so it couldn't have reflected images of galaxies.

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