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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

#471

Post by astroH »

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…

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.

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

#472

Post by __alexs »

skykooler wrote: post #257
hutzlibu wrote: post #241

Earlier quoted context omitted.

It is not, because ice has a smooth surface and that probably the surface layer melts a bit because your shoes are warm? That would be my reasoning, but it likely seems to be wrong, well why?

If that were the case, then cold things wouldn't slip on ice, but they do (for a demonstration, pick up a rock that's been sitting out in the cold and note that it still slides on ice)

I'm not sure a cold rock sliding across very cold ice will slide any better than if the ice was another very large smooth rock. Ice is hard and smooth. Hard smooth things have low friction.

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

#473

Post by mkl »

Cthulhu_ wrote: post #427
Dopameaner wrote: post #324

Earlier quoted context omitted.

I always wondered if we could somehow get a James webb telescope revolving around all planets of our solar system in the next 1000 years. That should give us pretty awesome visuals.

I want to venture that 1000 years is pessimistic. I just hope governments or private entities open up their wallets to build and launch more and better telescopes. I'm reading the whole JWST project is estimated to cost $10 billion. That's about 4.4 overpriced Twitters, 77 US Department of Defense budgets (just for 2023), and 11.7 Facebook annual revenues. We have the technology and the means, what's lacking now is t…

Your maths is upside down, I think. $10 billion is 10/44 ≈ 0.227 overpriced Twitters, 10/816.7 ≈ 0.0122 US DoD budgets, etc.

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

#474

Post by pwatsonwailes »

0xbadcafebee wrote: post #43
twawaaay wrote: post #23

Earlier quoted context omitted.

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…

if time is a dimension, and we can only see the past and the present, could it not be that, if one's gaze were shifted, one could see the future? effectively looking at the "other side" of the dimension of time? looking straight at one "side" of time, you can only see the past and present. but if you had a galactic set of mirrors set up around "time", couldn't you "see" the other side where the future lies? effective…

Time doesn't exist as a thing in the way you're thinking about it. It's why in physics we talk about spacetime. (The following is not entirely accurate and an oversimplification.)

Space and time are one thing, which have to be thought about together. Your current thinking imagines that you're in a box, with x, y and z coordinates, and that time is a thing passing inside it. Instead, it'd be more accurate to talk about that you're in a frame of reference with x, y, z and a, and all are tied together. There's no sense in which you can talk about space and not also be talking about time, and vice versa. For a similar idea, a 3d volume is not a plane plus a z axis, where you can talk about moving through just the x and y axis without the z axis mattering. You can talk about a view of that, but it doesn't mean the z axis isn't relevant. Ask two planes not colliding whilst viewed from above how important a z axis is. (Maths jokes are the worst.)

The actual physics involved for discussing this gets absurdly complex very quickly, but this is about as simple as I can think how to explain it whilst still being in the bounds of accurate.

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

#475

Post by mr_mitm »

narag wrote: post #302
TheOtherHobbes wrote: post #151

I'm going to be very amused if the Steady State Model - an unpopular relic from the 1940s - turns out to be correct. https://en.wikipedia.org/wiki/Steady-state_model

The funny thing is that since we've been observing the universe for so little time, and we're so small, most of the evidence for the big bang and expansion is not direct , but a chain of deductions. I mean that we can't observe the expansion because we can't really triangulate at galactic scale. If there is another reason the light from distant galaxies turn to red, kind of a long-distance light fatigue, we couldn't…

> The reason I always heard that would be a confirmation, because it comes from a different causal path, was precisely the different composition of old galaxies

And you never heard of the CMB? That's generally considered the "smoking gun" evidence for the big bang.

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

#476

Post by mr_mitm »

Buttons840 wrote: post #264
azalemeth wrote: post #228

Earlier quoted context omitted.

My favourite example of the intractabilities of some theories is that magnetohydronamics apparently can't predict the formation of streamer jets when you put your finger on a kid's plasma ball – i.e. the main point of the toy is beyond the most advanced theory that lies behind NIF, JET, ITER, etc...

At this point in the thread, I'm wondering if we do a disservice to physics students by making it appear we have it all figured out.

Who do you think makes it appear we have it all figured out? That is not my impression at all. All the scientists I know are extremely aware of the limitations of their field.

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

#477

Post by sebzim4500 »

6nf wrote: post #256
rqtwteye wrote: post #234

Earlier quoted context omitted.

As far as I know , MOND is not compatible with some observations. So dark matter and MOND have to be tweaked to agree with what we see.

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 between MOND + new particle vs new particle.

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

#478

Post by nine_k »

deepsun wrote: post #343
dark-star wrote: post #208

Earlier quoted context omitted.

My favorite theory is that the universe is finite, some sort of (hyper)sphere or -torus. If we could just look far enough out there we would see our own galaxy What would be even cooler is if it was warped like a moebius strip in a higher dimension, so that when we look out there, everything is mirrored from "our" reality :-D

That assumes that we can somehow see through time, which leads to a whole bunch of inconsistencies (aka time travel paradoxes). There's no way to look through large distances without looking back in time, unfortunately.

I don't see how seeing one's past may lead to paradoxes. Meddling withthe past would still be impossible, due to the,distance and the speed of light limit. What am I missing?

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

#479

Post by moloch-hai »

eru wrote: post #444
whatshisface wrote: post #407

Earlier quoted context omitted.

I think the OP was talking about the bacteria that derive non-negligible sustenance from viruses. > Moreover, our foraging trials demonstrated robust growth in the Halteria population with only chloroviruses as food (rint = 0.66 ± 0.26 [SD], black lines, Fig. 1A), with minimal to no growth in the controls (with chloroviruses filtered out; rint = 0.22 ± 0.12 [SD], blue lines, Fig. 1C). The abundance of the larger Para…

Yes, I know. That's why I wrote >> Up until last year nobody had thought to see whether anything eats viruses! Turns out some do. > Nah, lots of things eat viruses. It's nothing unusual at all. You eat viruses, I eat viruses. They are everywhere, after all. > The novel finding was a critter that lives / can live solely on viruses.

You wrote it, but it was what we all understood already, making writing it nothing but an exercise in snark.

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

#480

Post by denton-scratch »

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)

> So such an expansion phenomenon should affect everything uniformly right?

Apparently not. As far as I can tell (IANAC) cosmic expansion affects the empty space between galaxies, but not concentrations of mass. Galaxies (and everything in them) are immune to cosmic expansion.

I understood that cosmic expansion is a consequence of General Relativity; DE is supposed to explain accelerating expansion. Is that right? But wouldn't expansion result in there being more empty space and less nearby stuff; and therefore in accelerating expansion?

I wish I understood this stuff.

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