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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

#261

Post by sfifs »

Twisol wrote: post #204
sfifs wrote: post #131

Earlier quoted context omitted.

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)

Gravitational attraction still dominates on even fairly large scales, and chemical bonds absolutely dominate over anything expansion could possibly do -- it would contribute an incredibly light force opposing any bonds. So no, we (and our galaxy) are in no danger of being inflated from the inside by space itself.

Thanks for the explanation!

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

#262

Post by paulrouget »

xenadu02 wrote: post #213
sfifs wrote: post #131

Earlier quoted context omitted.

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)

The strong nuclear force, electromagnetic force, and even gravity are strong enough to overwhelm the expansion within individual galaxies and even local groups of galaxies. In other words the expansion of spacetime very very very slightly tries to shift the atoms of your body apart but we can't even detect it because ordinary forces like chemical (electromagnetic) bonds are exponentially stronger - enough to pull thi…

I don't think that's true. Expansion is not very weak around matter, it just doesn't exist. It sounds a little counter intuitive to think that expansion "shutdowns" as we get closer to galaxy. But that's because expansion and gravity are a little more complicated that just a force.

We over simplify what expansion really is, which leads to this type of thinking.

Expansion and gravity are results of the same equations.

Einstein equations are difficult to use, so we usually split the results in two models, FLRW (empty space) and Schwarzschild metrics (around matter). Computing the equations leads, respectively, to expansion and gravity. And it's not like there's one and the other, with gravity fighting expansion. It's "one or the other".

Around matter (in Schwarzschild metric), solving Einstein questions, we see zero expansion drifting. If there is matter, there is gravity, and no expansion.

Quoting Wikipedia [1]:

> Once objects are formed and bound by gravity, they "drop out" of the expansion and do not subsequently expand under the influence of the cosmological metric, there being no force compelling them to do so

[1]: https://en.wikipedia.org/wiki/Expansion_of_the_universe#Effe...

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

#263

Post by throwawaymaths »

sebzim4500 wrote: post #75
aeneasmackenzie wrote: post #63

Earlier quoted context omitted.

"dark matter but not as much" is still an improvement if you replace it with something better. If MOND predicted these observations and LCDM didn't it's reasonable to say that it is better.

Yeah that's fair. I guess it could also explain why DM has been so hard to pin down, if both MOND and DM are true then there might be DM candidates that have been unfairly ruled out. I do think it significantly hurts the (more philosophical) argument that MOND is simpler or has fewer parameters than DM though.

So the ongoing problem with LCDM is that the parameter space for allowable particles keeps getting pushed back. We keep falsifying classes of potential particles that could be WIMPs. MOND+ some standard model-adjacent particle (like say right handed neutrinos), if we can have a phenomenological estimate of how much of them should exist, would at least be credible on account of having a constrainable set of parameters, whereas the density of WIMPs in normal LCDM has no constraint besides the same measure that we have to infer its existence (gravitation)

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

#264

Post by Buttons840 »

azalemeth wrote: post #228
sebzim4500 wrote: post #98

Earlier quoted context omitted.

I think this says less about cosmology and more about the incredibly effectiveness of the standard model in the regime we can test directly on earth. If we compare ΛCDM to most other scientific theories it doesn't look so bad in terms of discrepancies. Certainly there are many unexplained effects in solid state physics, there isn't even an accepted explanation for why rubbing a balloon on your head makes it stick to…

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.

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

#265

Post by kgc »

vl wrote: post #198
sebzim4500 wrote: post #98

Earlier quoted context omitted.

I think this says less about cosmology and more about the incredibly effectiveness of the standard model in the regime we can test directly on earth. If we compare ΛCDM to most other scientific theories it doesn't look so bad in terms of discrepancies. Certainly there are many unexplained effects in solid state physics, there isn't even an accepted explanation for why rubbing a balloon on your head makes it stick to…

>Certainly there are many unexplained effects in solid state physics Wait for it… Why ice is slippery? Usual explanation is completely incorrect. Actual semi-conclusive research just recently happened.

Link to the research?

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

#266

Post by darkerside »

Sharlin wrote: post #253
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?

The usual hypothesis is that a microscopic layer of the surface melts, not because your shoes are warm, but because of the pressure. But the pressure is not enough to do that. That said, as anyone who has been in icy conditions can attest, it is clear that ice at ~0° C is vastly more slippery than at, say, -20°C.

My understanding is that, at the borders, master is constantly changing between its states. A boiling pot has water molecules turning to steam, as well as vice versa. It just has more of the first probabilistically.

Maybe the same happens with ice and water.

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

#267

Post by rsj_hn »

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.

Which researchers (as opposed to pop-sci pundits) think MOND is a better explanation than Dark matter?

That is a very, very fringe alt-science view that so far exists in various pop-sci blogs and informal youtube discussions, rather than in mainstream conferences, journals, and research centers.

I'm not saying it's bad to speculate or write whimsical blog articles about these topics, there's lots of room for creative speculation, but MOND does not respect Lorentz invariance which is basically a deal breaker for virtually all serious researchers. Fewer things have more robust empirical support than Lorentz invariance, so discarding it forces you to say that your violation is always just over the horizon of what is testable (and this horizon keeps getting pushed back). That's generally a discrediting feature of any theory and a huge red flag. Much better to say "you don't know" than to postulate something which requires such massive fine tuning to always be just beyond the horizon of what is testable, but close enough to that horizon to have explanatory power for observed phenomena.

https://phys.org/news/2017-11-evidence-violation-lorentz-inv...

https://asfriedman.physics.ucsd.edu/Papers/Friedman+2020a.pd...

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

#268

Post by scotty79 »

tomp wrote: post #190
dougmwne wrote: post #174

Earlier quoted context omitted.

Here’s the important point I think you are missing. You are looking in TIME, not in space. When you look very far away, you are looking back to the beginning of time, back to a singularity where all matter and energy existed at a single point. In every “direction” you end up looking back to the same time and the same place, the beginning of everything. There’s nothing “beyond” that, it is the beginning. If you ask, w…

But if we're looking in the direction of a galaxy far far away (i.e. 14bn ly away) (which we don't know it's there, but let's assume it is, because likely some galaxies must be there), how come we see the CMB, which is 13.7bn years old, and not the galaxy itself, which is (by definition) less than 13.7bn years old?

Because what we see from that direction are the things that were there in the last 13.7bn years. But the farther we look we see older images. So while we can see image from 10bn years ago of something that's 10bn light years away, when we try to see something 13.7bn light years away we just see microwave soup because that's what was there 13.7bn years ago. And if we try to see something 14bn light years away we see nothing from there because 14bn years ago there was nothing there.

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

#269

Post by RosanaAnaDana »

dinkumthinkum wrote: post #120
RosanaAnaDana wrote: post #97

Earlier quoted context omitted.

>If you give GPT3 code with a bug in it, and ask it to find the bug, it can't really do that. The hell are you talking about? I've been doing this literally any time I need something fixed and it does just fine.

It doesn’t solve non-trivial bugs. It can bugs that match patterns that have been asked a lot if Stackoverflow or something like that.

I love the sound of goal posts as they go whooshing past.

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

#270

Post by scotty79 »

UltraViolence wrote: post #189

So there could've been civilizations that are literally BILLIONS of years ahead of us? Imagine what these people know about the universe! This reminds me of the Star Wars lead-in: "A long long time ago in a galaxy far far away." It really could've happened you know!

I don't know. Life needed almost 5bn years to get to this point on Earth. Let's say we lucked out and it almost always takes 3 times as long. Then we look like early birds in the Universe.

What's more, earlier solar systems had a bit boring chemistry. We need a lot of supernova made stuff to really function so this narrows the time window.

You might think that near galactic core there's a lot of really cool stuff made but I think interstellar environment might be less stable because of that and maybe life doesn't even have a 5bn years of quiet time to develop there.

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