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Webb and Hubble confirm Universe's expansion rate

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Re: Webb and Hubble confirm Universe's expansion rate

#171

Post by rihards__ »

techwiz137 wrote: post #37
kromem wrote: post #4

Earlier quoted context omitted.

Basically it means that we can't regard the Hubble result as a mismeasurement and the age of the universe seems to be different depending on how you measure it. From the article: "The bottom line is that the so-called Hubble Tension between what happens in the nearby Universe compared to the early Universe’s expansion remains a nagging puzzle for cosmologists. There may be something woven into the fabric of space tha…

I just think it means the expansion rate is not a constant, but a variable.

I kind of agree with this conclusion.

Before we know better it can be just that spacetime was expanding at a different rate (we still would need at least one another Planck that operates in roughly same range to confirm this).

Hubble wavelenght range - 0.1 to 0.8 μm Webb wavelenght range - 0.6 to 28.3 μm Planck wavelenght range - 330 to 10000 μm

My understanding is that Planck was observing photons that have happened much more earlier.

Re: Webb and Hubble confirm Universe's expansion rate

#172

Post by hnfong »

Sprocklem wrote: post #168
k7sune wrote: post #132

Earlier quoted context omitted.

“Degrading” sounds very intuitive to me. Can the frequency of the light waves simply slow down over a very long distance/time? Or maybe the speed of light simply slows down over an unimaginably long distance? We don’t have any model to describe such behavior, but everyday objects around us all slow down one way or another, what makes light so different?

IIRC, this was one of the explanations proposed when the existence of a red shift was first noted: that the light is somehow slowly losing its energy over very long distances, becoming “redder” as it did so. It ultimately lost out to the dark energy / space-time expansion theory, although I do not recall why. Presumably there was some observation that precluded “degrading” light from being the sole explanation.

https://en.wikipedia.org/wiki/Tired_light

Re: Webb and Hubble confirm Universe's expansion rate

#173

Post by jMyles »

willis936 wrote: post #129
pdonis wrote: post #122

Earlier quoted context omitted.

I'm not sure what you mean by "phantoms in the data". The distribution of stress-energy is a free parameter in GR; it has to be inferred from observations. The terms "dark matter" and "dark energy" are just names for, respectively, "stress-energy that acts like the matter we can see, but we can't see it", and "stress-energy that acts like a cosmological constant". Neither of those things poses any problem for GR, sin…

>"Dark matter" poses a problem for particle physicists, who have so far been unable to find any fundamental particles that would produce the observed properties. It's clear to me why we haven't made any new discoveries in cosmology in the past two decades. It's this exact attitude of "the model is the truth". All models are wrong. The data can help you improve it, but you have to at least want to improve it.

> we haven't made any new discoveries in cosmology in the past two decades

Is that true?

At least for my hobbyist understanding of the progress of cosmology, quite a lot seems to have happened in the past two decades. Confirmation of the Higgs Boson at CERN [0] kept me up all night to watch the press conference; I found it extremely exciting. (Maybe you count this strictly as observational particle physics and not cosmology, but I might appeal for it to be allowed in the context of your critique).

And what of TFA? Isn't what we're reading now a new discovery in cosmology?

What about the rush of exoplanet discoveries?

What about the dramatically different galactic properties now observed in increasingly strange corners of the observable universe (including some which perhaps give insight into some of the properties of "dark matter" or whatever it ends up being)?

0: https://home.web.cern.ch/news/news/physics/new-results-indic...

Re: Webb and Hubble confirm Universe's expansion rate

#174

Post by hnfong »

sophacles wrote: post #152
willis936 wrote: post #129

Earlier quoted context omitted.

>"Dark matter" poses a problem for particle physicists, who have so far been unable to find any fundamental particles that would produce the observed properties. It's clear to me why we haven't made any new discoveries in cosmology in the past two decades. It's this exact attitude of "the model is the truth". All models are wrong. The data can help you improve it, but you have to at least want to improve it.

What do you think they do now? How do you propose they do it differently? What evidence do you have that what they are doing now doesn't work, and does the all the evidence of how they work support your hypothesis? Be detailed, because your comment just has some motivational speaker nonsense but no depth. For example, in the last 20 years cosmology has: + Refined its model of stellar formation based on observational…

People can be right about problems with a process or way of thinking without being the next Einstein. There's no need to get personal.

Re: Webb and Hubble confirm Universe's expansion rate

#176

Post by hnfong »

Veserv wrote: post #68
explaininjs wrote: post #26

Earlier quoted context omitted.

> Of course, all the results have error bars. Not to mention the underlying philosophical assumptions, such that the "rate of time" has been constant across all of... time. Aka: How do we know a "year" 13 Billion "years" ago bears any resemblance to one now? What would it mean for it not to?

Well for one, if the laws of physics are not time invariant (i.e. the laws of physics are not the same at all points in time) then energy can be created or destroyed [1]. So that would be quite a shocker. [1] https://en.m.wikipedia.org/wiki/Noether%27s_theorem

Saying "X is true because otherwise, it would be quite a shocker" isn't really a proof.

It's almost an appeal to common sense. (which, admittedly, is often the best argument we have). IMHO there's often a bit of over-confidence among scientists about the universe being 13 billion years old and what happened during the Big Bang, if it just relies on such a common sense argument.

I know it's unscientific to suggest maybe laws of physics are not time invariant across such scales, because until we have a time machine we can't test this theory, but then flipping the argument (that laws of physics are definitely time invariant) is also technically unscientific -- we're basically assuming this without strong evidence.

This goes back to the old debate on the problem of induction in science, (see David Hume, Karl Popper, etc.) and I think it isn't emphasized enough in modern discussions that, perhaps, there's a small chance that these foundational concepts in physics could be invalid.

Re: Webb and Hubble confirm Universe's expansion rate

#177

Post by jMyles »

explaininjs wrote: post #170
fooker wrote: post #32

Earlier quoted context omitted.

Philosophical indeed, as it's impossible to define the idea of a rate of time, when the idea of rate is defined in terms on time itself.

Yes, an external reference clock is needed. If a computer chugs along doing { counter++; } at 1 clock cycle per clock cycle for 13.7 billion clock cycles, it will think 13.7 billion clock cycles have passed when counter is 13.7 billion. On the other hand, if a computer chugs along at one clock cycle per clock cycle for 1 clock cycle, and reads &counter and sees 13.7 billion, it will think 13.7 billion clock cycles ha…

I agree with you 100% on your assessment of what can be known, but I think I disagree nearly as strongly on your assessment of the humanity that springs from attempting to know it.

To exist in the state you describe - with neither start state nor isolation level measurable in any tamper-proof way - and to yet still dedicate one's life to observing and pondering the complexity of the resulting cosmos is, to my eye, laudable and beautiful.

Where you see hubris, I see humility. Everyone who attempts to expand the corpus of human understanding of cosmology knows that the endgame is somewhere short of perfection. And yet they are inspired to carry on. It seems to me that matters of state, economics, medicine, technology, and many other fields will benefit from a similar disposition.

Re: Webb and Hubble confirm Universe's expansion rate

#178

Post by oneshtein »

__turbobrew__ wrote: post #163
narag wrote: post #105

Earlier quoted context omitted.

How do we know that galaxies are accelerating away from us and not moving at constant speed? There's a more basic question: How do we know the galaxies are moving? It seems (I haven't seen any other response, like... ever) that we have one and only one way to measure the speed of galaxies: the red shift. It's impossible to triangulate those huge distances and the time scale would also be a barrier, so no way of confi…

Degrading light sounds like an interesting idea to me, you could call it the “cosmological damper” if you will. Thought experiment: imagine you have light particles in a perfectly circular orbit around a black hole. Does the light ever fall into the black hole or does it orbit for eternity?

There a whole set of theories, called "Tired light" theories, which tries to explain Cosmological Red Shift by degradation of photons with time. Buy they require whole set of different cosmological principles: a medium for light propagation is required to dump lost energy into, no Big Bang. But even with a tired light theory, galaxies are accelerating toward attractors, see https://arxiv.org/pdf/1702.02483v1.pdf https://www.youtube.com/watch?v=NpV0GQo3P0c

Re: Webb and Hubble confirm Universe's expansion rate

#180

Post by oneshtein »

jMyles wrote: post #173
willis936 wrote: post #129

Earlier quoted context omitted.

>"Dark matter" poses a problem for particle physicists, who have so far been unable to find any fundamental particles that would produce the observed properties. It's clear to me why we haven't made any new discoveries in cosmology in the past two decades. It's this exact attitude of "the model is the truth". All models are wrong. The data can help you improve it, but you have to at least want to improve it.

> we haven't made any new discoveries in cosmology in the past two decades Is that true? At least for my hobbyist understanding of the progress of cosmology, quite a lot seems to have happened in the past two decades. Confirmation of the Higgs Boson at CERN [0] kept me up all night to watch the press conference; I found it extremely exciting. (Maybe you count this strictly as observational particle physics and not co…

Yes, it's true. Mainstream science refuses to accept anything radically new because of huge baggage. Nobody wants to look stupid, then relearn, recalculate, republish, reteach everything, or lose their tenures, grants, etc. It's why science advances in small incremental steps. AFAIK, there is a team of scientists secretly working on radically new set of theories (I got contact but cannot join because of war).
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