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A new estimate of the Hubble constant – the rate at which the universe is expanding – is baffling many of the finest minds in the cosmology community
[...] "The fact the universe is expanding is really one of the most powerful ways we have to determine the composition of the universe, the age of the universe and the fate of the universe," said Professor Adam Riess, at the Space Telescope Science Institute in Baltimore, Maryland, who led the latest analysis. "The Hubble constant quantifies all that into one number."
In an expanding universe, the further away a star or galaxy is, the quicker it is receding. Hubble's constant – proposed by Edwin Hubble in the 1920s – reveals by how much.
So one approach to measuring it is by observing the redshifts of bright supernovae, whose light is stretched as the very space it is travelling through expands. A challenge, though, is pinpointing the exact distance of these stars.
Riess, who shared the 2011 Nobel Prize for Physics for providing evidence that the expansion of the universe is accelerating, is part of a team focussed on developing ultra-precise methods for measuring distances.
The latest Gaia observations have advanced this effort by identifying dozens of new Cepheid stars, which have the special feature that their light flickers at a rate that is directly linked to their brightness at source. So through observing the pulsations of these so-called standard candles, scientists can work out their original luminosity and, therefore, how far away they and their native galaxies are.
The new data puts the Hubble constant at 73, which translates to galaxies moving away from us 73km per second faster for each additional megaparsec of distance between us and them (a megaparsec is about 3.3m light-years).
However, a separate estimate of Hubble comes from observations of the Cosmic Microwave Background, relic radiation that allows scientists to calculate how quickly the universe was expanding 300,000 years after the big bang.
"The cosmic microwave background is the light that is the furthest away from us that we can see," said Riess. "It's been travelling for 13.7bn years... and it's telling us how fast the universe was expanding when the universe was a baby."
Scientists then use the cosmic equivalent of a child growth chart (a computational model that roughly describes the age and contents of the universe and the laws of physics) to predict how fast the universe should be expanding today. This gives a Hubble value of 67.
Until recently, scientists had hoped that as measurements became more precise, this mismatch would narrow, but instead the difference has widened and the latest calculation gives a chance of only 1 in 7,000 of the discrepancy being down to chance. "If this continues to hold up we may be dealing with what we call new physics of the universe," said Riess.
[...] The crisis in cosmology, as it was described a meeting of the American Physical Society last month, could soon be resolved through new measurements of the Hubble constant based on gravitational wave observations by the Ligo collaboration. "Within the next five years, we'll probably nail this," said [John] Peacock [professor of cosmology at the University of Edinburgh].
(Score: 3, Funny) by c0lo on Friday May 11 2018, @08:29AM (2 children)
Fucking shit, who can comprehend such distances?
Say it for the layman: a parsec is a bit more than 1/12 Millenium Falcon Kessel run.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by BsAtHome on Friday May 11 2018, @09:55AM
Well, it is like a walk in the park. It may seem like a long walk, but once you are out and going you will find the actual distance to be getting smaller.
Please beware that walking at speeds that compensate for the red-shift may cause bugs in the park to pass right through you. You have been warned.
(Score: 4, Informative) by DannyB on Friday May 11 2018, @02:05PM
I don't want megaparsecs, I prefer Attoparsecs. [wikipedia.org]
Very conveniently, 1 attoparsec per microfortnight is 1.0043268 inches per second. Very close.
When trying to solve a problem don't ask who suffers from the problem, ask who profits from the problem.
(Score: 3, Interesting) by stormwyrm on Friday May 11 2018, @11:32AM (4 children)
One possible explanation for this discrepancy in measurements of the Hubble Constant is that the Milky Way and most of the nearby galaxies are actually inside a big void [soylentnews.org] (the KBC void). So that means if you try to measure the Hubble Constant by observing relatively nearby galaxies also inside the void, you'll get a higher estimate of the Hubble Constant, since these galaxies will in general be receding from us faster, because they'd be experiencing extra acceleration from the gravity of the mass at the edge of the void. Cepheid variables can only be seen in relatively nearby galaxies, so if the hypothesised void is real, measuring the HC that way will yield a higher value. But if you observed something at the edge of the void or beyond (> ~1 billion light years), like the Cosmic Microwave Background or supernovae in very distant galaxies, you might get the smaller value of the Hubble Constant. I don't know if anyone has tried to measure the Hubble Constant by using observations of only extremely distant supernovae that should be beyond the edge of the KBC void, but if they did get the same lower value of the Constant as we see when trying to measure it with the CMB, then well, that's pretty good evidence of a Hubble bubble [wikipedia.org].
Numquam ponenda est pluralitas sine necessitate.
(Score: 1, Interesting) by Anonymous Coward on Friday May 11 2018, @12:44PM (2 children)
Except that the gravitational effect of a hollow sphere on masses inside it is exactly zero. So you don't get acceleration towards the edge.
The reason is that while the near edge is nearer, the far edge has more mass in the same solid angle. While the attraction per mass goes like 1/r², the mass per solid angle goes like r², so the product is constant, and thus the forces from both sides cancel exactly.
(Score: 2) by hendrikboom on Friday May 11 2018, @02:07PM (1 child)
The boundary of the void may not be a sphere. It may not even be evenly populated.
(Score: 2) by maxwell demon on Friday May 11 2018, @02:47PM
But then you'll get an inhomogeneous acceleration towards specific places (like the Great Attractor [wikipedia.org]), not a homogeneous acceleration towards the edge. Of course such inhomogeneous acceleration can be identified and calculated out of the equation (guess how they found the Great Attractor?).
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by arulatas on Friday May 11 2018, @02:04PM
I believe you mispronounce Hubba Bubba https://en.wikipedia.org/wiki/Hubba_Bubba/ [wikipedia.org]
----- 10 turns around
(Score: 2) by looorg on Friday May 11 2018, @11:59AM (15 children)
So the answer to life, the universe and everything might be 73, or 67 or 42. Why does it have to be just one of them? Can't we just declare that it's an non strict interval between 42 and 73 or that it's an array {42,67,73} ?
(Score: 0) by Anonymous Coward on Friday May 11 2018, @12:39PM
You mean binary tree.
(Score: 3, Touché) by realDonaldTrump on Friday May 11 2018, @12:44PM (4 children)
69 was tremendous for me. And 71 is amazing!
(Score: 0) by Anonymous Coward on Friday May 11 2018, @01:34PM
I'm sure it was, unfortunately it apparently wasn't earth moving for Mrs. Daniels.
(Score: 2) by stretch611 on Friday May 11 2018, @04:05PM (2 children)
2019 will be great for the rest of us. (after you are impeached.)
Now with 5 covid vaccine shots/boosters altering my DNA :P
(Score: 2, Offtopic) by realDonaldTrump on Friday May 11 2018, @05:20PM (1 child)
We both know the 115th Congress isn't going to impeach me. Because I have too many loyal guys & gals in there. The 116th starts on Jan. 3. And maybe the VERY CROOKED Dems will rig enough elections, get enough seats, that I could be impeached. That could happen. You know that there's a trial, right? And believe me, I have the best lawyers. And I could lose, that's so true. Anybody could lose when a bunch of very unfair Dem Senators are making the decision. But if I stay in office past Jan. 20, .@VP [twitter.com] Pence is eligible for two full terms as President. After he finishes out my term. President Clinton -- Bill Clinton -- loves the women, he has a lot of fun with the women. And he got in a little bit of trouble over that. And I love the women, I've had some very good times with the ladies. I'm amazing with the ladies, as everybody knows. A sex god. Maybe I'll get impeached for that, who knows, right? But Mike Pence, he does what they call the Billy Graham rule. Meaning, he's never alone with a woman, except Karen. He's never had sex with a woman, except Karen. He's never had a blowjob. Never done anal. And obviously no gay stuff. The Dems try to get him on sex stuff, they'll be laughed out of office. They impeach me, get ready for almost 10 years of President Pence. Enjoy!!!!
(Score: 0) by Anonymous Coward on Friday May 11 2018, @09:30PM
and I prefer you to pence anyday. he looks and behaves like a sith like emperor palpatine
(Score: 1, Funny) by Anonymous Coward on Friday May 11 2018, @12:44PM (4 children)
Why can't the answer be a vector?
(Score: 4, Funny) by DannyB on Friday May 11 2018, @02:10PM (1 child)
I can't stand the stress of a vector victor. That would make me tensor and tensor.
When trying to solve a problem don't ask who suffers from the problem, ask who profits from the problem.
(Score: 2) by All Your Lawn Are Belong To Us on Friday May 11 2018, @03:14PM
Roger, Oveur.
Done, Dan.
This sig for rent.
(Score: 2) by looorg on Friday May 11 2018, @03:08PM (1 child)
Vectors imply force, which makes the answer to life kinda rapey ...
(Score: 2) by DannyB on Friday May 11 2018, @04:41PM
Maybe a tuple which is less stressful than a tensor.
When trying to solve a problem don't ask who suffers from the problem, ask who profits from the problem.
(Score: 2) by PiMuNu on Friday May 11 2018, @12:47PM (2 children)
I think the point is that there is evidence for a non-constant constant i.e. new physics (variable speed of light etc).
(Score: 2) by arulatas on Friday May 11 2018, @02:06PM (1 child)
Does this mean that "light speed" travel might be possible as the speed of light may be variable depending on local conditions?
----- 10 turns around
(Score: 2) by ben_white on Saturday May 12 2018, @03:53AM
No. Spacetime can expand faster than the speed of light, but nothing can move through spacetime faster.
(Score: 2) by All Your Lawn Are Belong To Us on Friday May 11 2018, @02:59PM
I hereby declare a new unit of Belongies (B). One B is a set range between 1.595 and 1.738 km/s/∆MPc
You may now rest assured that The Answer can be expressed as 42 B by itself, with my compliments. You may even just leave off the unit designation since everybody knows what a B is now.
This sig for rent.
(Score: 2, Informative) by ngc3242 on Friday May 11 2018, @04:30PM (2 children)
Back in the 2017-11-02 issue of Nature, a paper was published based on LIGO measurements of an event in a relatively nearby galaxy (NGC 4993) that puts H0 at 70 km/s/Mpc (+12/-8).
The preprint of the paper is at https://arxiv.org/abs/1710.05835 [arxiv.org]
The actual paper is at https://www.nature.com/nature/journal/v551/n7678/full/nature24471.html [nature.com]
They're waiting for more events to narrow the error bars.
(Score: 2) by HiThere on Friday May 11 2018, @04:41PM (1 child)
The problem is, as stated in a post above, "Why can't the results be a vector?". I realize that this would violate the Copernican hypothesis, but there's really only a very small amount of data that indicates that space has no preferred orientation. So it could well be different along different axis of measurement. (IOW, a vector.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 0) by Anonymous Coward on Saturday May 12 2018, @05:57AM
"only a very small amount of data". you mean like angular momentum conservation? yeah, that's only an approximation.