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It used to be 13.7 billion years+- a big margin that got narrowed down to 13.8+- a smaller margin. Not seeing that changing unless there's something seriously wrong with the previous research.
Narrowing it based on what we can measure doesn't mean it's correct.
The deeper we have stared into the universe the more our base understandings have challenged.
Hence the "unless there's something seriously wrong with the previous research" part. That is always a possibility, of course, but it's much less likely that is the case then that this single study is the thing that is wrong.
More likely it’s this guy’s research.
So insane man, love it. Hard to comprehend and just to think about.
What about what the CMB tells us? Theory seems to ignore that entirely. I'll wait for the cosmic neutrino background before I take any of these articles more seriously.
Are there any constants that we actually know to have varied along the lifetime of the universe?
According to my understanding, yes. For example, it is usually assumed that there was a period of time shortly after inflation when matter was in a quark-gluon plasma, which would imply a larger strong coupling than today, since a small strong coupling is associated to confinement. There was also the electroweak-epoch, during which the electromagnetic and weak interactions were unified, and the corresponding gauge bosons were massless. The masses of the W and Z bosons can thus also be regarded as time-varying, as well as the electron charge. However, it should be noted that these changes are not all that significant on the cosmological scales under investigation here (e.g. the quark epoch ended at about 10^-6^ seconds after the big bang, which is much much less than the age of the universe, and it's assumed that it still took quite a while before the first stars formed). A time-varying cosmological constant could potentially be much more relevant (and some quantum gravity theories even predict it), and I've heard some people suggesting it as a potential solution for the H0 tension. However, I unfortunately can't access the paper and assess what precisely the author did there, and whether it is in any way similar to what I just mentioned.
What you're talking about is the energy dependence of the coupling constants, which is a phenomenon that is very well understood theoretically, and also checked in experiments. The early universe was much hotter, and thus particles had much more kinetic energy and "felt" slightly different coupling constants. The neat thing is that, since this is a purely energy-dependent effect, we can recreate the conditions of the early universe: the collisions at LHC have an energy of the order of 1 TeV, which corresponds to a temperature of 10^16^K, the temperature 10^-12^ s after the Big Bang. Anything after the first 10^-12^ s we can directly recreate, and from 10^-12^ s to about 10^-30^ s-ish we can more or less reliably extrapolate. And of course this is all included in the standard Lambda-CMD cosmology.
Although the article is behind a paywall (which is somewhat strange in cosmology, but I digress), you can check other articles by the same author that also use the "varying constants" framework, for example https://arxiv.org/abs/2201.11667. His framework is that the speed of light c, the Planck constant h, the Boltzmann constant k and the Gravitational constant G depend directly on time, or to be more precise, on the expansion factor of the universe. There are two big differences with respect to what you were saying:
- c, h and k are not coupling constants, and therefore they don't receive any energy-dependent corrections. In fact, you could think of these constants as "conversion factors" between units: c converts space-time coordinates in seconds to space-time coordinates in meters, k converts kinetic energy in Joules (or electronvolts) to kinetic energy in Kelvin, and h converts angular momentum or action measured in quanta to angular momentum or action measured in J·s (or eV·s). Honestly it doesn't make much sense to me that these constants could change (what does it means, in physical terms), that they could change in a correlated way, or that they could change in a correlated way to one, and only one, coupling constant, G.
- Since this is a time-dependent change, there is no real way to significantly test the hypothesis (unlike the energy-dependent changes). We can not go back in time, or to wait to a different time when these constants would be different. He actually proposes to study how the experimental determinations of these constants in the last 10-20 years, which sounds very wild, as those tiny differences are very susceptible, by definition, to experimental uncertainties, and they are not very suitable for controlled tests.
Thanks for giving additional explanation. I was trying to keep my reply relatively short and agree with most of what you said.
Although the article is behind a paywall (which is somewhat strange in cosmology, but I digress), you can check other articles by the same author that also use the “varying constants” framework, for example https://arxiv.org/abs/2201.11667. His framework is that the speed of light c, the Planck constant h, the Boltzmann constant k and the Gravitational constant G depend directly on time, or to be more precise, on the expansion factor of the universe.
Thanks for the arxiv link. I was aware that some people did stuff like this (time-varying fundamental constants), but the abstract only speaking of "coupling constants" made me think of Λ (and G), not fundamental constants. There are some theories that motivate a varying speed of light, for example (Hořava–Lifshitz gravity comes to mind), but this doesn't seem to be motivated by any theory in particular, as far as I can tell. I also agree with you that it seems quite weird to give c, h, and k a time dependence each, only to then have them all be functions of G.
Since this is a time-dependent change, there is no real way to significantly test the hypothesis (unlike the energy-dependent changes).
I'm not sure if I fully agree with this. Shouldn't varying c, h, and k with time clearly change any observable related to the dispersion of light and gravitational waves, or black body radiation (among many other things)? And if we had access to even just one of those from different times during cosmological evolution (where the change should be much larger than between a few decades in the present), we should in principle be able to check if the proposed scaling law holds quite easily. Of course, the author could always make the variation with time small enough to avoid contradicting experiment (which would make it indeed unfalsifiable in practice), but that seems to go against the main idea of using these time-varying fundamental constants to explain some aspects of cosmological evolution. My guess now would be that the paywalled paper modifies the relation between redshift and time to undo the "damage" done by modifying the constants. Nevertheless, it wouldn't surprise me much if this kind of scaling is already ruled out implicitly by some data, as I can't imagine it not affecting a lot of different observables, but maybe I'm also overestimating the experimental cosmological data available at present, or the strength of the variance the author proposes.
Somewhat. Based on my understanding of current astronomy news (I'm not an astronomer, just interested in the field) it's not proven, but it's not entirely disproven either. For instance, my understanding is that the Hubble constant (rate of expansion of the universe) is different if measured with the Cosmic Microwave Background (newer universe) compared to measuring redshirt of stars (older universe). Of course, it could be that one of the measurements made an assumption that's not true, but i don't think it's out of the question that the false assumption ends up being that the constant stays the same over time...
Take what I say with a grain of salt, though. Hopefully an actual astronomer can pitch in
"Hubble constant" is a misnomer, and an old fashioned term. Cosmologist actually use the term "Hubble parameter" (which is in general time dependent except in very specific models which only contain dark energy), and denote its present value as H~0~.
https://en.wikipedia.org/wiki/Hubble%27s_law#Time-dependence_of_Hubble_parameter
I don't know if this counts as a constant, but I read that time moved something like 5 times slower in the early years of the universe.
It didn’t as time is relative just like space. There is no absolute standard of time to say “time moves faster”. Faster relative to what?
Yeah, you're right. I guess it's 5 times slower relative to how we perceive now, so it's definitely not a constant.
https://phys.org/news/2023-06-quasar-clocks-universe-slower-big.html
Exited for more news
I've been watching progressively more complex videos on YouTube about spacetime over the past two years.
The more I understand of it, the more I realize I understand nothing of it.
It bends my mind so much, it's like taking weed without any physical substances.
It makes the Total Perspective Vortex seem like a walk in the park.
A lot of theories come along, few survive scrutiny of people who know what they’re doing
I’m not surprised at all honestly
It sounds insane to say, but 13.4 or whatever felt way too young
“Feels” and “common sense”means little in science unless you have a mathematical or logical reason why you feel that way. I’ve seen far too many metaphysical theories try to be taken seriously to not point out that “feels” is useless, observation and math are what matter
And yet, some of the greatest scientific discoveries of all time were made based on people’s feelings and intuition. Fucking shocker I know right. I’ll bet you’re fun at parties.
Despite agreeing with your initial position, you sound like an asshole at parties and outside of them, too. If you need to posture and belittle to support your position, then you have no business trying to argue it in the first place.
Intuition can be a powerful compass to guide us to truths we haven't yet considered, bubbling up from our subconscious that contains the bulk of our brain's processing power. But the other commenter is right, it's not infallible. That same intuition in different people came up with all of science's knowledge (both the stuff that is currently believed and the stuff that has since been disproven) as well as all of religion's knowledge (assuming there isn't any higher being involved, which my intuition says there isn't but others' have come to different conclusions).
Double that is still weird. If the heat death of the universe is 10^100 years out or more, we're incredibly early whether it's 13 billion or 26 billion. That leads to one possible explanation for the Fermi paradox, the universe will have countless civilizations rise and fall over the eons, we're just one of the first, if not the first.
Granted that's just a thought that came to mind under the influence of an unexpectedly strong edible rather than actual scientific research, but it's still neat.
Well, it would be most logical for it to have existed forever.
For the last 13.7 billion years, we haven't observed matter/energy just popping into existence. In all that time, nothing was truly created from scratch.
So, it would be quite the exception to the rule, if that was different beforehand...
A sincere thank you for a fascinating, quality post in Technology instead of the usual Threads/Twitter/Reddit posts.
Before Hubble and also before JWST scientists predicted these telescopes would :
Hypothesis : show evidence of the beginning of the universe at about 14 billion years.
Observations again and again nulifies that hypothesis.
Scientist goes over the top about this in part because they have :
human needs
need to publish, need to make a career, need to be recognized as scientists, need to put bread on the table
And so they come up with this :
BigBang, acceleration of the expansion : "inflation of the universe", decceleration : "end of the inflation", and now a new phase of acceleration !
Since there is not enough strong non-contradictory evidence to say otherwise, let's go with Ocam's razor : whatever more simple theories, even if it hurts scientist's egos.