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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

#521

Post by cryptonector »

fartsucker69 wrote: post #436
habibur wrote: post #416

Earlier quoted context omitted.

Any straight line you draw from earth to any direction in the sky will then reach a star.

Which is insanely far away and all light coming from there will have diminished in energy enough to be barely visible? Inadequate explanation. Even if the universe was a closed box with perfectly reflecting borders, what you would actually see in the sky is something like an average brightness of the entire universe with some fluctuations.

Photons do not "diminish" in energy except via red shifting (where does the energy go? into the expansion of the universe!).

Light scatters, gets absorbed and re-emitted, it's true, but if distances don't change then the universe would still be much brighter than it is today.

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

#522

Post by cryptonector »

narag wrote: post #497
cryptonector wrote: post #408

Earlier quoted context omitted.

> If there is another reason the light from distant galaxies turn to red, kind of a long-distance light fatigue, we couldn't really know. It's not just red shift that demands an explanation, but also that the sky (space) is dark. If space wasn't expanding then the skies would be bright white. Another thing is the second law of thermodynamics, which very strongly implies a lot of standard cosmology. Of course, standar…

It's not just red shift that demands an explanation, but also that the sky (space) is dark. If space wasn't expanding then the skies would be bright white. Another thing is the second law of thermodynamics, which very strongly implies a lot of standard cosmology. Don't you feel that these evidences just make a case from models checked in small scales and tell the whole universe what it should do? I don't mean the rea…

> Don't you feel that these evidences just make a case from models checked in small scales and tell the whole universe what it should do?

Yes, we like to think that the laws of physics we can deduce locally are global. That could be wrong, for sure. But consider that we understand the physics of our solar system (which has a star), and we see other stars in the skies which... implies that at least as much of our local physics that makes stars possible also applies where we see those stars.

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

#523

Post by actionfromafar »

kepano wrote: post #369
karmelapple wrote: post #304

Earlier quoted context omitted.

Which itself is based off the intro the film Contact: https://youtu.be/EWwhQB3TKXA

Which is inspired by the Powers of Ten 1977 short: https://youtu.be/0fKBhvDjuy0

In the 1954 book Horton Hears a Who its entire universe is inside a speck of dust.

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

#524

Post by 6nf »

sebzim4500 wrote: post #477
6nf wrote: post #256

Earlier quoted context omitted.

MOND is not compatible with all observations but neither is dark matter. A lot of scientists think MOND is a better explanation than a new particle that we've not yet observed. Have a look at Sabine Hossenfelder's work for some of those arguments.

First, it might be 'a lot of scientists' in absolute terms because this is such a fertile field, but it is a tiny minority of cosmologists who believe MOND is the best explanation for these effects. Secondly, even the proponents of MOND concede that you need to introduce some amount of dark matter in order to explain e.g. observations of the Bullet Cluster. So the competition isn't between new particle vs MOND, it is…

Sabine says the Bullet Cluster is a problem for dark matter EVEN MORE than it's a problem for MOND!

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

#525

Post by ngcc_hk »

gala8y wrote: post #510
astroH wrote: post #460

I have to say, this article is exceptionally disappointing. As someone who works in this space, there are numerous misleading depictions about the state of the field. Almost any respectable simulation shows that disk galaxies are widely present at very early times. This is simply an argument of angular momentum conservation and these rotational states are simply more transient at early times compared to the local Uni…

Honestly, thank you very much for this comment. As a lay person, I very often fall into taking such news as solid, as am kind of hoping for some great breakthroughs in cosmology (broadly speaking). Thanks for providing details. "One particular problem is correlated hot pixels" has a nice, cooling effect on me and I get the idea that it is an unsolved issue (kind of get it). Same with "experts only believe those with…

The need of counterpoints and different views are important especially in academic field. But some debates got us lost as well. I would not say bad against YT but more about lack of quality one. Hope that will come.

Take an example of MONO discussed below. One claimed it is right but wrong in other prediction.

“ So MOND does predict more galaxies at high redshift however it also predicts earlier reionization than LCDM which it turns out not to be true and the mass function of clusters is not what we see purely based on X-ray temperatures. So getting one thing right at the expense of many others doesn't make this particularly viable.”

But the major discussion shifted to dark energy and refracted … and totally ignored that wrong predictions by mono … it is just hard to follow the threads.

But more discussion may help.

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

#526

Post by moffkalast »

bmitc wrote: post #504
moffkalast wrote: post #495

Earlier quoted context omitted.

I was pretty convinced that dark matter is made up nonsense and that RelMOND is probably correct, but then I learned of the Bullet cluster. https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to... Two clusters collided, with most of the observable objects being just past the middle point right now, however most of the mass seems have already shot way out to the edges, as if it passed right through everything.…

> however most of the mass seems have already shot way out to the edges, as if it passed right through everything. It's pretty hard to explain with anything else other than that there's something there that has mass yet can't interact with anything else that passed through everything when the collision happened. It is my understanding that dark matter does interact gravitationally, so I am confused by this.

I should've been clearer there, "has mass" would mean that it interacts gravitationally and has inertia while moving. But that's about it, from what I understand.

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

#527

Post by ngcc_hk »

jquery wrote: post #377
idlewords wrote: post #325

This was predicted by astronomer Stacy McGaugh on his super interesting blog as a natural consequence of modified Newtonian dynamics ( https://tritonstation.com/2022/01/03/what-jwst-will-see/ ). McGaugh came to support MOND over dark matter reluctantly for just such reasons—MOND routinely predicts things in advance that dark matter struggles to justify ex post facto, usually by adding additional moving parts to the m…

It seems to me, as a layperson, if MOND was hypothesized first, it would be the dominant theory. It’s so elegant and simple with so much explanatory power. However, because it was hypothesized much later, the fact it matches past predictions is given no weight, despite its simplicity. I think this is a bit of a mistake. I believe that simplicity itself is evidence. Dark matter theory is starting to feel like the epic…

Epicycles is what Copernicus fought against. Have he also have some I am not aware of ?!

Epicircle come about if one consider earth is the Center and some planets sometimes move backwards and then start to move forward again. You do not have that issues with Copernicus.

But he made a mistake of using circle. The observation guy using everything rotate around the sun and sun around the earth … a wrong model but the key is not the model but the observation he made. His record keeper Kepler finally found some other patterns and Newton get the … the rest is history.

I do not go to wiki or internet to check out the phrase. But epicircle …not of Copernicus.

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

#528

Post by shagie »

sfifs wrote: post #131
shagie wrote: post #68

Earlier quoted context omitted.

That rate is "only" approximately 68 kilometers per second per megaparsec. 68 kps isn't that fast (it's about the same speed as the Helios 2 solar probe) and a mega parsec is big distance (3.2M light years). Its that there's a lot of megaparsecs between here and there and the sum of all of those 68 kps is more than the speed of light. The relevant Kurzgesagt : TRUE Limits Of Humanity – The Final Border We Will Never…

So such an expansion phenomenon should affect everything uniformly right? Are we (people /animals) then getting "bigger"? Over time innthe extreme will it cause problems in signal transmission in our own nervous systems (since apparently we have a problem seeing light beyond the observable limit)

(a follow up...)

If that question is of interest to you, PBS Space Time - Could the Universe End by Tearing Apart Every Atom? https://youtu.be/gEyXTQ9do-c gets into the "what if" of dark energy and its influence on matter.

You'll note that it isn't until the very end of the instant before the Big Rip that that make it so that the expansion of the universe that it overcomes the strength of chemical bonds.

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

#529

Post by moloch-hai »

HPsquared wrote: post #483
moloch-hai wrote: post #279

Earlier quoted context omitted.

Magnetohydrodynamics is, specifically, the "easy part" carved out of plasma fluid dynamics. It is inadequate to almost all applications, with only rare, precious exceptions, mostly manufactured. Devices that rely on plasma fluid dynamics to work are carefully designed to keep the plasma in the domain where MHD can be used to model them. Astrophysicists, as a rule, hate to be obliged to consider phenomena that involve…

Is it called "hydrodynamics" because of an assumption of incompressibility (like regular hydrodynamics vs aerodynamics)?

It has several commonly unphysical assumptions, including infinite conductance, "freezing" the magnetic field in a chosen frame, and assumptions about time and length scales.

"Effects which are essentially kinetic and not captured by fluid models include double layers, Landau damping, a wide range of instabilities, chemical separation in space plasmas and electron runaway."

That electrons are 1836 times less massive than the lightest positive charge carrier is neglected. Accelerated, they strike positive and neutral particles and knock loose more electrons.

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

#530

Post by drdeca »

eigenket wrote: post #217
drdeca wrote: post #201

Earlier quoted context omitted.

What’s wrong with it being (topologically) a 3-sphere ? That seems plenty symmetric to me.

Theres nothing massively wrong with it, it's a perfectly plausible model. The one thing that isn't particularly nice is that spheres have intrinsic curvature, essentially if you draw two parallel lines on a sphere they will eventually touch. We can go and look at astronomical data and see if the universe has any intrinsic curvature that we can see. People did this and it turns out that from all the astronomical data…

Ahhh, yes parts of that sound familiar. So, the reason we can (at least pretty much) ~~rule out~~ a 3-sphere [EDIT: I didn’t read carefully, and missed the “it could be a really really big 3-sphere so that the curvature is close enough to zero” part], is because you can’t have a flat sphere,

But you can have a flat torus (or some other shapes that “wrap around”), but we have different reasons to disbelieve those shapes (the “looks the same in any direction” and “looks the same in every position” expectations).

Cool, thanks!

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