Live data from Hacker News

The James Webb Space Telescope is finding too many early galaxies

skyandtelescope.org

271–280 of 547 posts

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

#271

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.

If it was all figured out why get into the field? Sure some do it just to know. But the hunt is what drives most.

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

#272
post #198

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.

I had to look that up. Here's research[1][2] from 2019 about "why ice is so slippery", including some of the apparent surprises. I dunno. I'm not a physicist so some of the surprises seem like very minor things to me.

Spoiler: According to this research, ice is slippery because of a thin layer of water. (As we expected, no?) But the water layer is 1) thinner than expected, 2) more viscous than expected, and 3) contains bits of ice which help make it extra slippery.

> "Usual explanation is completely incorrect."

Only for an unusual definition of "completely" IMO. Again, IANAP.

[1] https://phys.org/news/2019-11-ice-slippery.html

[2] https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.041...

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

#273
post #244

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!

Earth came quite late to the party and it spawned life relatively soon after. That's why it's strange we haven't discovered any Dyson spheres/swarms (in any galaxy). Either life is indeed absurdly rare, or Dysons are impractical for some reason, or there is a way to mask heat.

Earth life uses lots of different elements - at least two generations of supernovas required. Not really that late if you allow for that.

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

#274

Earlier quoted context omitted.

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.…

That makes a lot of sense -- thanks for contributing that nuance!

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

#275

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.

So much this! There’s surely a huge argument that all of scientific education is a massive disservice.

The point should be to learn and appreciate the method or process of scientific investigation of uncertain and mysterious or hard to understand phenomena.

Instead we get dogma as a proxy of measuring intelligence with little regard for what the fundamental tools are of being a scientist.

I’ve gone all the way through to Grad School and came out astounded at just how little commitment to or a sense of the essence of scientific investigation and what’s expected of the investigator there is in the system. They don’t prepare you for it because they themselves weren’t prepared. You can try to leverage some meta understanding of the “process” in conversation or debate, but so often the conversation falls flat because few are prepared or accustomed to it. Research is often done, IMO, in philosophical poverty by people eking out a living in the gutters of novelty and paradigmatic safety, averting their gazes from the sky (flourishes aside, you get my point).

Putting aside the health of actual research. If the general public is to benefit from education and pass that benefit into their society (that’s the point right), it needs to be more than soon to be forgotten and often useless fallacies.

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

#276

Earlier quoted context omitted.

> because the light from it won't reach us. This is one of the most interesting aspects to the universe. It's not, "because the light from it hasn't reached us yet but is on the way and will get here eventually." Rather it's that the rate of expansion of the universe is accelerating, so that we're moving away from parts of it faster than its light can cover the distance to us. It will never reach us. That's mindboggl…

So mindboggling that frankly I refuse to accept it. The likelyhood that we'll figure this out in my lifetime is zero, but I simply can't comprehend a universe that accelerates without cause (dark energy) infinitely. Just as we don't understand the root causes of dark energy, I believe it's just as logical to believe that something will eventually slow it down. I have to believe that because only a cyclical theory of…

I think it’s actually quite a simple model to think of the universe as a network of discrete nodes, rather than a spatial thing that’s expanding and within which various things are accelerating. It makes the Big Bang simpler - we start from a small number of nodes and they grow in number, so we don’t need to think about what the universe is expanding ‘into’. And it explains expansion - nodes can divide like mitosis, so we don’t need to explain some force pushing things apart.

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

#277
post #211

Earlier quoted context omitted.

I feel for the Weather pattern folk. All of the one I have spoken to over the years are pretty cool. They are trying to model an insanely complex system - oh but thanks to global warming they are struggling to make models that work for longer than a few years because it all keeps changing!

If “it all keeps changing”, which thwarts their attempts to “model an insanely complex system”, then wouldn’t that mean any claim about “global warming” is actually a claim to possessing a priori knowledge?

No as has already been answered. The example I can directly think of is modelling of specific weather patterns across Australia. A model that works in predicting weather 2 weeks out may work today but not work so well in 5 years.

Global Warming is happening, that is not just a realm of modelling but is directly observable today. The models on a broad scale look to be working very well, specific locations and reactions not so much.

It is possible to make broad engines that work but also get the finer details wrong. Signal : Noise ratio and all of that.

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

#278
This can further reinforce the idea that the unobservable universe was always there and that the big bang is only a pattern of movement of the cluster of galaxies and it is only the information that has managed to arrive from our position.I want to see how big bang theory falls into an optical illusion.

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

#279

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...

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 plasma fluid dynamics, even what can be shoehorned into MHD. Such phenomena are thus orphaned, and you won't find anybody talking about them.

The exception is solar physics, where nothing can be done at all without fully general plasma fluid dynamics. Solar physicists have the largest gonads in science, on par with rocket propellant chemists.

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

#280

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.

The pressure from well distributed static load divided by area is not, but on the tiny scale where the difference between grippy and less grippy surfaces happens there isn't so much "well distributed" going on. And once you add lateral force to the mix all bets are off: there will always be a point getting better grip (is surface interference the correct term?) than others, see a local force concentration and when that causes a tiny spot of phase transition there will very soon be a new point of least local slippyness getting all the attention of lateral force.
Post reply on HN