Adam Riess and the Hubble tension
79 comments
·May 30, 2025otherayden
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observationist
Archive link: https://archive.is/51R4k
cogogo
Reminded me of this thread from a couple of days ago. Interesting that both Riess and Gough argue there's a sociological phenomenon amongst cosmologists. Though who knows what Riess might think of the "blowtorch theory." https://news.ycombinator.com/item?id=44115973
antognini
I have a phd in astronomy and I spent some time reading it yesterday. I don't think he'd think much of it. The theory seems to be aimed at explaining the existence of cosmic voids and the structure of the cosmic web. But these are pretty naturally explained by lambda CDM. And if the goal is to explain away dark matter, there are other pieces of evidence for dark matter that wouldn't be explained by this theory. At any rate, as far as I can tell it's not a quantitative theory so it would be hard to tie it to observations.
snowwrestler
Every scientist knows there is a sociological component to the practice of science. This is not a novel or noteworthy observation and I don’t think Riess was intending it to be.
mr_mitm
Also, every cosmologist knows the standard model is not the final answer. I think the author is really trying to overstate the controversy.
cogogo
But many non-cosmologists like me aren’t so aware. Many of us learned basic physics where the standard model is treated as a given. Or the standard if you don’t mind dad jokes.
cogogo
I happen to not be a scientist but found the observation interesting given the overlapping subject matter. Especially given the stark differences in training/background. E.g. scientist/not scientist.
amai
Adam Riess might be right, but for reasons he won‘t like. Much of his measurements (and also his Noble prize) depend on the supernovae 1a, which according to the standard model are standard candles. That means it is assumed they always reach the same luminosity, so they can be used to measure distances in the universe (the fainter they are, the farther away they are).
However what if supernovae 1a are not standard candles and their luminosity varies over a much greater range? Then a lot of distance measurements from Riess et. al. are wrong. I belief that scenario to have higher probability than many of the proposed alternatives. But Riess cannot see that, because it would put into question his lifes work.
tshaddox
> For nearly a century, astronomers have known that the universe is expanding, because the galaxies that we can see around us through telescopes are all rushing away. Riess studied how they moved. He very carefully measured the distance of each one from Earth, and when all the data came together, in 1998, the results surprised him. They were “shocking even,” he told his colleagues in a flustered email that he sent on the eve of his honeymoon. A striking relationship had emerged: The farther away that galaxies were, the faster they were receding. This “immediately suggested a profound conclusion,” he said in his Nobel Prize lecture. Something is causing the expansion of the universe to accelerate.
I'm quite confused by this early paragraph. It seems to be claiming that Hubble's law was discovered in 1998 by Adam Riess, instead of in the 1920s by Edwin Hubble (and others).
CGMthrowaway
It's the second derivative.
Riess et al's findings showed that galaxies farther away are not just receding faster (as Hubble's Law already described), but that the rate of expansion itself is increasing over time. This discovery suggested the presence of a mysterious force, now called dark energy, driving this acceleration.
This was unexpected because most astronomers at the time thought the expansion should be slowing down due to gravitational attraction between galaxies.
mr_mitm
Yes, but the article is indeed unclear about this. In particular this line:
>The farther away that galaxies were, the faster they were receding.
This is already the case in Hubble's law, which says that the velocity is proportional to the distance. Hubble's constant is the proportionality constant and thus the expansion rate.
Riess found that the Hubble constant is not constant. Instead, the expansion rate is increasing over time.
mathattack
How many journalism majors did you encounter in undergrad who knew how to apply second derivatives to Physics problems? (I've given up on pop science articles - podcasts with experts interviewing experts has a much higher signal to noise ratio)
geokon
But further away galaxies are further back in time, so if the expansion is accelerating.. shouldn't they be going away at a slower speed, and the closer galaxies going away from us at a faster speed?
trhway
>but that the rate of expansion itself is increasing over time.
Take for example galaxies running from us at "c". They happen to be exactly at 13.7B light years - coincidence? I don't think it is a coincidence, and some simple logic leads to conclusion that the same galaxies will be running from us at the same "c" say 300M years later - ie. then it will be "c" at 14B light years distance from us - which means that the Hubble constant is actually decreasing.
dataflow
I think they're talking acceleration, not velocity? Hubble's law says more distant galaxies are receding faster than slower ones at some calculable rate, but it doesn't say the rate at which they're doing that is accelerating over time. (I do find it kind of shocking that one can prove this without observing the same thing over a prolonged period of time.)
marcellus23
Disclaimer that I'm not an astronomer and might be totally wrong, but from some quick searching, it seems like the article is conflating Hubble's discovery and Riess's. Hubble's law can be true even if the expansion of the universe is slowing down, not speeding up: a galaxy twice as far away as another can be receding at twice the speed, even if that speed is decreasing over time. But it seems like Riess's discovery is that the speed is actually increasing over time. It's related to Hubble's law but not the same thing.
Frankly, the fact that I could find that out with 2 minutes of reading Wikipedia reflects pretty poorly on the author.
tinix
The Hubble Tension is not Hubble's constant.
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gamesetmath
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hn_acc1
I guess they've watched the expansion between two galaxies over time and found it increasing?
Otherwise, the fact that "the further away from us they are, they faster they were receding" made me think of this way:
-the further away they are, the longer the light had to travel to get here
-the longer the light had to travel, the longer it took to get to us
-the longer it took to get to us, the further into the past we are looking
-the further into the past we look (further distances), the faster they are receding - doesn't that imply it was faster in the past? The further past we look, the faster it is. The closer we look to home (the closer to "now"), the slower it is.
ianburrell
Galaxies farther away are receding faster because they are older. What Riess found is that it isn't linear with distance, they are moving away at an accelerating rate. I assume this shows up with close galaxies moving faster than they should.
The acceleration was really fast after Big Bang, but slowed down. It was assumed that it would flatten out and expand at constant rate.
zvorygin
I wish the journalist asked the leading scientists in the field “Before you learned of the Hubble tension, what did you think the odds were of the standard model being correct? And after?”
And everything would be much clearer.
antognini
I think it's still not universal among astronomers that the Hubble tension is real. (Though the tide seems to have shifted in the last two years or so with the median astronomer reluctantly accepting that the Hubble tension is probably real.)
pavel_lishin
All of this is wildly exciting - I wonder if this is how people in the 1800s and 1930s felt like, as electricity and nuclear science was going through its hey-day.
spauldo
Your time's a bit off - electrification didn't really take off until the early 20th century and nuclear applications outside of weapons until the 1950s and 1960s.
My grandmother grew up when cars were scarce, electric wires were stapled to the wall, and indoor plumbing was for city folk. She hit a certain level of technological advancement and then just stopped, probably around the 1980s. She died last year, having never used the Internet or a computer and still using a console TV (with an adapter box installed by the cable company).
gaoshan
The description of how the universe is expanding sounds like how an explosion expands. Rapidly then slower until it settles down and stops (with no collapse at the end, just matter in place where it landed). I wonder if that could be the closest analogy?
pavlov
An explosion has a center. I'm not a cosmologist, but my understanding is that the universe expands everywhere and at a rate that's in fact accelerating rather than slowing down.
dylan604
What does the has a center comment have to do with the rest of the comment? The big bang had a center too. That doesn't mean anything in the context though.
mr_mitm
The other two sibling comments expressed some doubt, but I can tell you with absolute certainty that in the standard model, and to the best of our knowledge in reality, the big bang did not have a center.
Aloisius
I thought the big bang had no center because there is no edge. Rather expansion was of space itself that happened everywhere.
meroes
I don't think the big bang or the universe ever had a center.
BurningFrog
Riess' original discovery is the opposite: The universe expands faster and faster over time.
boxfire
Is there any succinct publication of his observations?
A_D_E_P_T
There's a "general audience" review by the man himself.
begueradj
Very well written. I felt like reading a good novel.
lproven
Paywall bypassed:
Archive link using a tool I built to automatically redirect to archive links :)
https://unbloq.us/https://www.theatlantic.com/science/archiv...