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Astrophysicists Puzzle over Webb’s New Universe

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Re: Astrophysicists Puzzle over Webb’s New Universe

#131

Post by Tazerenix »

somenameforme wrote: post #96
Tazerenix wrote: post #34

Earlier quoted context omitted.

The evidence for the big bang is generally not that if you look far enough back in a telescope, the universe looks younger, which is somewhat the layperson's confusion. Evidence for the big bang is about measuring redshift of galaxies throughout universal history, homgeneity and thermal equilibrium of the universe and CMBR, which could only be explained by it all having been in a compressed location where it could re…

I think you're leaving out a major issue there. Homogeneity was not in favor of the big bang. It's actually a major problem - the horizon problem. [1] Parts of the universe (think opposite sides) are not causally connected. Even traveling at the speed of light, there would not be enough time for a particle in one side to reach the other since the birth of the universe. Yet the temperature within these regions is homo…

Yep, no doubt there are definitely issues with inflation. My main point is that the size of black holes in the early universe is largely orthogonal to the whole big bang/inflation debate. Even if the model changes, the lack of IMBH evidence means that any universal history model must have some kind of time asymmetry.

Re: Astrophysicists Puzzle over Webb’s New Universe

#132

Post by lioeters »

astro1234 wrote: post #40
6thbit wrote: post #15

That’s a beautiful article showcasing our predicament in having access to more information about the universe. Now i have to be the one to ask the dumb defensive question: what makes us so certain that we can trust what we see on James Webb? Can we definitely discard a measurement problem?

Not a dumb defensive question but you should know the nice thing about these experiments is the incredible amount of work that goes into calibration and understanding all error signals. Messing up the data analysis has major precedents. If you aren't familiar you should look into BICEP data in 2014, they thought they had observed primordial gravitational waves which would have been earth shattering. Instead they just…

There's so much to love about this comment, especially this part:

> Cosmology is one of the most beautiful sciences in my experience, precisely because we have such good ways to model the observations to probe various models, and you can treat the observations with Bayesian stats with virtually no risk of misspecifying your model, or, if you do find its misspecified, you have discovered something new about the universe.

What a great example of the scientific process, collectively discovering, questioning, challenging, making mistakes, correcting them, and gradually refining our knowledge and understanding. Even as an outsider I can see the beauty in this earnest pursuit of truth.

Not to mention the subject matter is just mind-opening. The more you know, the more strange wonders and mysteries you find. It's incredible to get a glimpse of it.

Re: Astrophysicists Puzzle over Webb’s New Universe

#133

Post by switchbak »

sulam wrote: post #97

I thought I read somewhere that many of these little red dots are turning out to be nothing more than bog-standard brown dwarfs in our own galaxy that are confusing the signal. These days we have some pretty powerful agents who can read these things faster than I can, so I went and found the paper: https://arxiv.org/abs/2506.04004 It turns out that brown dwarfs are actually corrected for, so my remembrance is correct…

That’s valuable: I thought the whole thing was dismissed based on the brown dwarf explanation, this is interesting that that’s not the case.

It’s hard to keep up with all the news, particularly so given all the slop floating around. YouTube in particular seems to have a bunch of AI channels that just talk about this endlessly.

Re: Astrophysicists Puzzle over Webb’s New Universe

#134

Post by thelastgallon »

theodorejb wrote: post #123
cogman10 wrote: post #83

Earlier quoted context omitted.

Are you kidding? An astrophysicist that could come up with a new model that explains the current data would win a Nobel prize and earth shattering levels of notoriety. The data found doesn't contradict the big bang in any shape or form. It does challenge beliefs around black hole formation. The reason for the big bang model is because based on all our measurements of all the visible universe, it appears that everythi…

The Big Bang is an almost infinitely malleable story, contorted to comport with almost anything we observe. But how is this useful? The predictions of this theory continually fail. The farther we look, the more we see stars, galaxies, black holes, and other structures that shouldn't exist according to this model. What if the universe doesn't have a naturalistic origin, but was created by God? How much greater would o…

Which God? There have been (and still are) millions/billions of them.

Re: Astrophysicists Puzzle over Webb’s New Universe

#135

Post by pohl »

IncreasePosts wrote: post #99
ramraj07 wrote: post #58

Earlier quoted context omitted.

There was never a time when a book gave the public an overview of the universe. ABHOT was so popular for being a book no one actually read, theres even an index named after Hawking due to it: https://en.wikipedia.org/wiki/Hawking_Index Did _you_ read that book? There however definitely was a piece of media that captured public minds and educated them about the cosmos. And that was the show Cosmos. The original of cou…

I knew dozens of people in my high school who actually read it. Maybe godel, escher, bach would be a better "book that people talked about but never read"

I was also tempted to offer GEB as a better example, although I’ve read it twice. Many bounce off of it.

Re: Astrophysicists Puzzle over Webb’s New Universe

#136

Post by somenameforme »

wwind123 wrote: post #115
somenameforme wrote: post #96

Earlier quoted context omitted.

I think you're leaving out a major issue there. Homogeneity was not in favor of the big bang. It's actually a major problem - the horizon problem. [1] Parts of the universe (think opposite sides) are not causally connected. Even traveling at the speed of light, there would not be enough time for a particle in one side to reach the other since the birth of the universe. Yet the temperature within these regions is homo…

I kind of understand your frustration about the ad-hoc nature of the Inflation theory. When I was younger I believed the truth must be simple and beautiful - if a theory is complex and ugly then it's not the real truth. But as I get older, now I think the universe is what it is. Things may or may not have a simple or elegant explanation. Theories exist to explain things and make predictions. As long they serve both p…

It's not just the ad hoc nature of the hypothesis itself, but also the subsequent ad hoc retrofits and fine tuning. With enough unconstrained fine tuning you can create a signal from noise, even when no signal exists. Take for instance the geocentric universe. Ptolemy's model was completely wrong in numerous ways beyond just assuming everything revolved around the Earth, but it was sufficient to make highly accurate predictions by excessively fine tuning the model to fit observations. And as new observations contradicted the model, all you needed to do was just add more epicycles to also make them fit.

Those retrofits (or the results they explained at least) were then were used as arguments in favor of the model, which is completely nonsensical and backwards. I think the most fundamental factor in good science is falsifiability. But if we just engage in and accept ad-hoc retrofits, then models become completely unfalsifiable. And at that point, what does science even mean?

Re: Astrophysicists Puzzle over Webb’s New Universe

#137

Post by thecommakozzi »

stouset wrote: post #113
hparadiz wrote: post #94

Little red dots are my favorite new concept in astrophysics. This idea that there could be so much matter orbiting a black hole that the matter reaches sun levels of pressure which in turn starts steller fission without there being an star. Mind-blowing

Yep, it’s a super cool concept. A black hole of a given size has a finite amount of matter that it can ingest over a period of time. Trying to stuff more matter into it causes an outward pressure from essentially the friction of the swirling mass of material falling in. This radiation pressure could in theory be great enough to start fusion as would happen in a stellar core. Also fun is that this puts a limit on the…

[dead]

Re: Astrophysicists Puzzle over Webb’s New Universe

#138

Post by 6thbit »

astro1234 wrote: post #40
6thbit wrote: post #15

That’s a beautiful article showcasing our predicament in having access to more information about the universe. Now i have to be the one to ask the dumb defensive question: what makes us so certain that we can trust what we see on James Webb? Can we definitely discard a measurement problem?

Not a dumb defensive question but you should know the nice thing about these experiments is the incredible amount of work that goes into calibration and understanding all error signals. Messing up the data analysis has major precedents. If you aren't familiar you should look into BICEP data in 2014, they thought they had observed primordial gravitational waves which would have been earth shattering. Instead they just…

Thank you for taking the time to answer, I rest assured in the fine grind of the astrophysics wheel now.

All those screwup stories are amazing to know about! really help with staying humble and trusting the (scientific) process.

Re: Astrophysicists Puzzle over Webb’s New Universe

#139

Post by lenkite »

hparadiz wrote: post #94

Little red dots are my favorite new concept in astrophysics. This idea that there could be so much matter orbiting a black hole that the matter reaches sun levels of pressure which in turn starts steller fission without there being an star. Mind-blowing

Will all matter in the universe just collapse into black-holes eventually ? It feels that way. And will all the black-holes then merge to form the Primordial Black Hole which will then explode to form a new universe ?

Re: Astrophysicists Puzzle over Webb’s New Universe

#140

Post by typeofhuman »

cholmdomsky wrote: post #95
typeofhuman wrote: post #33

Earlier quoted context omitted.

I'm not sure anything after the event horizon right? Since no light == no information.

Can magnetic fields escape, if their lines intersect the event horizon of a black hole?

I think not because light is also a field.
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