Even though the title is copied from the article, we should change the title to "New data indicates the Webb and Hubble telescopes agree on the universe's expansion rate, but not with the cosmic microwave background measurement based expansion rate"
Webb and Hubble confirm Universe's expansion rate
81–90 of 380 posts
Re: Webb and Hubble confirm Universe's expansion rate
#82A little background based on a few articles about this plus my recollection of PBS Space Time videos on this: There are at least two ways to try to figure out the rate of expansion of the universe (which is called the Hubble Constant). • From variations in the cosmic microwave background (CMB) which are the result of certain conditions in the early universe it is possible to figure out what the expansion rate should…
Could it be that nearby galaxies are akin to small angle approximations in spacetime trajectory, but as you get really far away (e.g. CMB) the perspective distortion increases hyperbolically? I notice that if you normalize the Hubble data by their Lorentz factor you get back a constant expansion rate: https://www.desmos.com/calculator/llhnja1ocb
Re: Webb and Hubble confirm Universe's expansion rate
#83Earlier quoted context omitted.
And not much longer before that the discussion was how long would the sun last - 5,000 years or so was the estimate if it was a big ball of burning gas (source: A scientific American article I read, wish I could find it again, hoping someone here knows)
I think it’s this one you’re referring to https://www.scientificamerican.com/article/experts-doubt-the...
That's the one, thanks, I've been looking for it for ages
Re: Webb and Hubble confirm Universe's expansion rate
#84Earlier quoted context omitted.
> we’ve been using the 13.8 billion cosmological age estimate ever since I started brushing up my layman's understanding of the subject. I remembered the age of the universe as as 13.7 billion years, but I wasn't sure why that was. Well, the initial WMAP results in 2003 supported an age of 13.7 billion years. Later results nudged this upwards to 13.8 billion years. Of course, all the results have error bars.
> 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?
I have had the same thought that primordial reality had the same timestream as us but it was much longer, like the first "year" of reality was far longer than one year today, just the thinking "could time have been shorter or longer, why not"
Re: Webb and Hubble confirm Universe's expansion rate
#85A little background based on a few articles about this plus my recollection of PBS Space Time videos on this: There are at least two ways to try to figure out the rate of expansion of the universe (which is called the Hubble Constant). • From variations in the cosmic microwave background (CMB) which are the result of certain conditions in the early universe it is possible to figure out what the expansion rate should…
There's a 'fringe' theory that the CMB is not the echo of the big bang but rather the redshifted black body radiation of intergalactic dust (apparently the numbers are about right). Although the primary proponent of this theory is trying to justify some sort of cyclic universe model with it, if my understanding is correct it would still be compatible with a 'standard' big bang that has the "longer" (aka galactic expansion) timeframe.
And in any case physics still needs to explain what happened to that blackbody radiation.
Re: Webb and Hubble confirm Universe's expansion rate
#86A little background based on a few articles about this plus my recollection of PBS Space Time videos on this: There are at least two ways to try to figure out the rate of expansion of the universe (which is called the Hubble Constant). • From variations in the cosmic microwave background (CMB) which are the result of certain conditions in the early universe it is possible to figure out what the expansion rate should…
Re: Webb and Hubble confirm Universe's expansion rate
#87Earlier quoted context omitted.
I’d assume that we have some notion of how the laws of physics have changed, if at all, since the Big Bang. We measure time in vibrations of a cesium isotope IIRC
Fun fact: the Oklo reactor, a naturally occurring nuclear reactor that was active more than a billion years ago, was used to test if physical constants were the same in ancient times. https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...
And we can split hairs and conclude that for "the last two billion years, on this planet, in this galaxy, the physics affecting nuclear decay have not changed"
It's great to know that say dating using carbon-14 decay is still useful over those time ranges on planet earth (I don't know if that is something we care about given that fossils don't tend to contain much carbon, but coal and oil deposits are around 400 million years old).
I don't want to imply that this is too small of a sample size, but I will imply that nuclear decay, and the movement of galaxies across the universe might be unrelated. Don't know. Not sure how we'd measure that. Supernova observations would tell us about nuclear fusion and it's limits. Does it tell us about nuclear fission? I don't know.
Re: Webb and Hubble confirm Universe's expansion rate
#88Earlier quoted context omitted.
This, together with the endless philosophising around dark energy, dark matter and whatnot paints a pretty strong arrow towards our models having some flaws when it comes to their large-scale application. I hope to live long enough to see where we made our mistake and get a better model.
Almost every model we build of more trivial things based on observation always turns out to be not really right. I cannot imagine why one of the universe that has had multiple version updates in the last 100 years to not also be grossly mistaken. I also don't expect the full model to be simple or beautiful. We may be thinking wishfully based on massive extrapolation and cutting corners to suit our narrow view into th…
I think the truth is likely that we live in a very complex universe that can be approximated by these sweeping laws in general, but is very "messy" close up. Consider that while the universe roughly obeys probabilities, it also has will and intent (to a degree we can debate in another conversation).
Re: Webb and Hubble confirm Universe's expansion rate
#89Even though the title is copied from the article, we should change the title to "New data indicates the Webb and Hubble telescopes agree on the universe's expansion rate, but not with the cosmic microwave background measurement based expansion rate"
That's a mouthful.
The title should be "Hubble Tension almost certainly not caused by measurement error."
Re: Webb and Hubble confirm Universe's expansion rate
#90I've asked this question before, but I don't think I received a good answer, so figured I'd try asking again. How do we know that galaxies are accelerating away from us and not moving at constant speed? People often point to the observation that the further away a galaxy is, the faster it appears to be moving away from us, implying acceleration. However, wouldn't we expect to see the same observation even without any…
I'm not an expert, but I think it's like this:
If the universe were expanding uniformly, we would see galaxies moving away from us. The further away they are, the faster they would move. Distance and velocity would have a linear relationship, with the Hubble Constant as the scaling factor.
But what we actually see is that, if we measure precisely enough, galaxies further away are moving faster than that. The conclusion is that the expansion is accelerating.