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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

#511

Post by throwawaymaths »

Beldin wrote: post #484
ndsipa_pomu wrote: post #455

Earlier quoted context omitted.

However, there is plenty of evidence to suggest that it does exist. The distribution of dark matter being uneven is evidence that something functioning like dark matter has to exist as MOND doesn't easily replicate that. Colliding galaxy clusters show a distribution of matter that differs from the distribution of visible matter, so the simplest explanation is that there is invisible matter that reacts gravitationally…

The simplest explanation is that there is regular matter which we fail to detect. Not weird, given the huge distances involved - there almost assuredly is mass that we didn't detect (e.g. planets). The point where fairy matter comes in, is that we can guess how bad we could be at not detecting matter. Basically, regular matter that we didn't observe can't explain everything - we would've observed it otherwise.

Sorry, There are currently hard constraints on the lumpiness and size on that matter which basically exclude all reasonable possibilities for "normal matter we fail to detect". It's certainly possible something strange is happening though, or our statistics could be wrong.

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

#512

Post by [deleted] »

Eduard wrote: post #113
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…

> there isn't even an accepted explanation for why rubbing a balloon on your head makes it stick to a wall But the accepted explanation is "static electricity", no? Or do you mean we don't "really" know when asking a couple of follow-up "why?" questions further?

[deleted]

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

#513

Post by throwawaymaths »

ndsipa_pomu wrote: post #455
throwawaymaths wrote: post #400

Earlier quoted context omitted.

The explanatory power of dark matter is so weak though. With the right clumping of LCDM you could probably also explain various reports of poltergeists around the world. Then you could claim that reports of poltergeists are evidence of LCDM over MOND because it's another phenomenon that MOND can't explain.

However, there is plenty of evidence to suggest that it does exist. The distribution of dark matter being uneven is evidence that something functioning like dark matter has to exist as MOND doesn't easily replicate that. Colliding galaxy clusters show a distribution of matter that differs from the distribution of visible matter, so the simplest explanation is that there is invisible matter that reacts gravitationally…

The evidence that it exists boils down to: gravitational anomalies. It's not multimodal, which is a problem because you're saying "it must exist because of x therefore it must exist" versus "it must exist because of x, which has a side effect of y, which aha also we see". That's why it's weak.

> the simplest explanation is that there is invisible matter that reacts gravitationally.

That's the whole point of the poltergeist example. If someone said: "Oh, that urn on your mantle just fell over? Must have gotten knocked over by a rogue ball of dark matter. The simplest explanation is that dark matter must exist". You would think they are insane.

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

#514

Post by foxyv »

moloch-hai wrote: post #288
foxyv wrote: post #196

Earlier quoted context omitted.

I think I got confused because I was thinking about why it stuck to the wall, rather than why it accumulated charge. I know why electrically charged objects stick to things. The why of how they got like that is a bit different as you mentioned. Triboelectric effect is spooky, but there are some theories. It's one of those non-linear messy quantum things that's a pain in the neck to solve.

> It's one of those non-linear messy quantum things that's a pain in the neck to solve. That is exactly equivalent to "dunno, maybe something".

> That is exactly equivalent to "dunno, maybe something".

Yup! It's like understanding the why of weather and people. They are messy and have so many factors you can't account for. It's like saying, why are the clouds shaped like that. You can why your way down, but it's turtles all the way!

When it comes to non-linear junk, the why becomes mixed up because the causes are so numerous. There are so many tiny interactions you can't really say there is one individual cause. Often times you have phenomena that occur at specific energy levels that aren't really caused by any one thing. Even something as simple as a double pendulum is unpredictable.

One thing that is kind of mind blowing is strange attractors. Systems that are so random you cannot predict them even a few moments later can exhibit seemingly ordered patterns. They seem to have a cause, but they are literally just statistical mechanics. A slightly more likely outcome out of un-countable numbers of other outcomes.

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

#515

Post by varjag »

rcme wrote: post #32
varjag wrote: post #31

Earlier quoted context omitted.

But MOND itself is a "retrofit" to make it agree with the data, isn't it? It's in the name.

Every theory is a retrofit. A useful theory is also predictive.

MOND has its share of failed predictions. It also still requires a certain amount of DM to work.

This is fine for work in progress that all frontier science is but the issue is far from settled.

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

#516

Post by ndsipa_pomu »

throwawaymaths wrote: post #513
ndsipa_pomu wrote: post #455

Earlier quoted context omitted.

However, there is plenty of evidence to suggest that it does exist. The distribution of dark matter being uneven is evidence that something functioning like dark matter has to exist as MOND doesn't easily replicate that. Colliding galaxy clusters show a distribution of matter that differs from the distribution of visible matter, so the simplest explanation is that there is invisible matter that reacts gravitationally…

The evidence that it exists boils down to: gravitational anomalies. It's not multimodal, which is a problem because you're saying "it must exist because of x therefore it must exist" versus "it must exist because of x, which has a side effect of y, which aha also we see". That's why it's weak. > the simplest explanation is that there is invisible matter that reacts gravitationally. That's the whole point of the polte…

You can think of dark matter as gravitational anomalies that aren't distributed uniformly. If we assume that physical laws are constant throughout the universe, then it becomes difficult to account for those anomalies without saying that there is "something" there that is influencing gravity. Obviously, we've labelled that "something" as dark matter and figured out what properties it can and can't have.

With your poltergeist example - if it was relatively common for urns on mantle to be knocked over, then it would make sense to come up with a hypothesis. If objects around the urn were affected gravitationally just before the urn falls over, then dark matter would appear to be a rational hypothesis.

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

#517

Post by ndsipa_pomu »

Beldin wrote: post #484
ndsipa_pomu wrote: post #455

Earlier quoted context omitted.

However, there is plenty of evidence to suggest that it does exist. The distribution of dark matter being uneven is evidence that something functioning like dark matter has to exist as MOND doesn't easily replicate that. Colliding galaxy clusters show a distribution of matter that differs from the distribution of visible matter, so the simplest explanation is that there is invisible matter that reacts gravitationally…

The simplest explanation is that there is regular matter which we fail to detect. Not weird, given the huge distances involved - there almost assuredly is mass that we didn't detect (e.g. planets). The point where fairy matter comes in, is that we can guess how bad we could be at not detecting matter. Basically, regular matter that we didn't observe can't explain everything - we would've observed it otherwise.

That's not the simplest explanation as our current theories limit the amount of normal matter that can exist and galaxies behave gravitationally as though there must be a lot more than normal matter. Normal matter that is invisible to us is not a viable solution to the evidence.

There some discussion of regular (baryonic) matter vs dark matter here: https://www.livescience.com/how-much-dark-matter-universe

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

#518

Post by dougmwne »

deepsun wrote: post #356
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…

To "what exists today, beyond 13.7 billion light years", I'd rather say that "it doesn't exist yet". Because, otherwise, it assumes there's some "global universe time" like UTC or something. But all there is is our light cone.

That is fair. We are veering into metaphysics or religion if we talk about what exists there today, or even if there could be any relationship between our “today” and their “today”. By definition there is no causal connection. I’ll get back to you on that once I finish inventing my Time Machine.

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

#519

Post by dougmwne »

Jeff_Brown wrote: post #194
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…

Is it true that space had no volume at the Big Bang? I understand that density rises without (known?) bound as we approach the Big Bang, but even if you compress infinite space by an infinite factor you might still have infinite space -- infinity divided by infinity is undefined.

If you run the density backwards far enough, eventually everything in the visible universe is effectively at a single point, in some theories this was modeled as an actual infinite singularity, but it’s quite possibly unknowable since our first evidence is the CMB 380k years into the whole thing. As we rewind time from there things being to get highly speculative.

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

#520

Post by ivalm »

afro88 wrote: post #462
ivalm wrote: post #86

Earlier quoted context omitted.

> I guess it's reasonable to assume that there are parts of the universe that are far older and much further away (ie, their light hasn't reached us yet). Which would mean we can never really guess the age of the universe. We can only guess the age of our local area? But older parts of the universe would emit light that would have more time to travel. So unless space is not continuous, we can confidently say that no…

But they can still be far away that the light hasn't arrived at us yet (or maybe never will?). It's entirely reasonable that space may not be continuous. There may be groups of galaxies far enough away from each other that they burn out before receiving the other's light. How can we confidently assume this isn't the case?

No, there was a time that all space was hot, and we know from microwave background radiation that it is homogenous. So it’s not just “galaxies are far from each other”, it would take “space time is discontinuous somewhere and this discontinuity is just on the edge of our observable universe”. There is also no older light that can ever reach us, as the amount of universe that is observable is actually decreasing (beyond that, CMB will always be the oldest light as it predates any astronomical object formation). Anyways, CMB really constraints the age/homogeneity of the early universe.
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