Tension in the Hubble Constant?
Things are moving at a pace in the debate about how fast the universe is expanding. The difference between 68 and 74 doesn’t seem important but that small difference is now the hottest argument in physics.
I have a special interest in it because ever since I published my paper “What is dark Energy” I have been predicting that there is no tension. The difference is real because Ho will increase towards the edge of our universe. Dark Energy is the gravitational pull of the cosmos.
I delayed publishing my paper back in January 2019 because yet another piece of evidence came out supporting my theory.
http://viXra.org/abs/1901.0451 What is Dark Energy?
‘On 28th January 2019 in Nature Astronomy, G Risaliti and E Lusso “Cosmological constraints from the Hubble diagram of quasars at high redshifts” arXiv:1811.02590, “measurements of the expansion rate of the Universe based on a Hubble diagram of quasars.” “a deviation from the ΛCDM model emerges at higher redshift, with a statistical significance of ~4σ. If an evolution of the dark energy equation of state is allowed, the data suggest dark energy density increasing with time.”
Which was exactly what I was saying.
Then in July this year a conference was organised in Santa Barbara and all the big players were there - Adam Reiss, Wendy Freedman, the HoliCOW team, Lloyd Knox of the Planck team and others. Oh to have been a fly on that wall.
The HoliCOW team has just published a paper supporting 74 and Wendy Freedman was presenting her paper using TRGBs. Now she came out bang in the middle at 70! (since then this has been challenged. If correct this would move the TRGB value up into the Reiss range.)
Only a few months later and we have two more papers measuring Ho.
Max Planck Institute September 13th. Two lens systems, 82 +/- 8
“Again this new measurement confirms that there seems to be a systematic difference in values for the Hubble constant derived directly from local or intermediate sources and indirectly from the cosmic microwave background,” states Eiichiro Komatsu, director at MPA, who oversaw this project. “If confirmed by further measurements, this discrepancy would call for a revision of the standard model of cosmology.”
Anowar Shajib et al on October 14th 74 +/- 3.
“Our measurement is consistent with that obtained from the previous sample of six
lenses analyzed by the Ho Lenses in COSMOGRAIL’s Wellspring (H0LiCOW) collaboration.
It is also consistent with measurements of H0 based on the local distance ladder, reinforcing the tension with the inference from early universe probes, for example, with 2.2σ discrepancy from the cosmic microwave background measurement.
Our paper measuring Ho from a new strong lens is out on arXiv:https://t.co/gHhiaAz5JX.”
Back to the conference where there has been some heated debate. Physicists have always defended their positions vigorously.
Scolnic, the SH0ES scientist and Riess collaborator, “Definitely a day unlike any day I’ve experienced,” he said. H0LiCOW’s new result felt to him like a year ago, what with Freedman’s TRGBs and Reid’s masers. “That’s three big hits all within the last week. And I don’t really know where we stand,” he said. Even if the discrepancy is real, “there’s no good story now which explains everything, on the theory or the observation side. And that’s what makes this so puzzling.”
Later in the conference two new measurements of the Hubble constant: A cosmic distance ladder calibrated with “Mira” stars gave 73.6, and galactic surface brightness fluctuations gave 76.5, both plus or minus 4.
With thanks to Quanta Magazine
The two early-universe predictions on the left side of the plot, with tight error bars around 67.4. Five late-universe measurements lined up on the right, around 73 or 74. And there in the middle was Freedman’s 69.8, the wrench in the works.
Since then two more measurements in the 70s and even 80s.
To quote Reiss from the conference “The choices now are either a conspiracy of errors, not just in one measurement but in multiple measurements . . . or there’s some kind of interesting new physics in the universe.”
And Freedman, “We’re working on pretty amazing data. Things that are telling us something about how the universe is evolving.”
Something is changing, and it's Ho.
I have always been a fan of Wendy Freedman. She even replied to an email and that is very rare. I am with her, “things are telling us that the universe is evolving”.
Our universe is accelerating at an increasing rate towards the Big Cosmos but no new physics is needed to explain it Adam Reiss. It’s just gravity, plain old gravity.
We do not need new physics, but we do need a new vision of the cosmos. The universe has always been much older and bigger than we thought. Such a simple idea but one that will need a major rethink of our cosmology. As such this idea will be ignored or attacked with all the force which physicists have always shown in defense of the old paradigm.
Final word from Wendy Freedman; "we need more data". If this tension is resolved then my idea is wrong; falsification. If Ho is variable then it supports me but doesn’t prove it. For that we may need Gravitational wave detection from out there in the cosmos.
It took half a century to build a machine to detect gravity waves. It may take another to build one capable of proving my theory, but we will not find unless we look.
The question “How big and old is the cosmos?” is the most important challenge cosmologists now face. If I am right then not only will we have resolved the enigma which is Dark Matter, but we will also know how our universe started and how it will end. We don’t need new physics we just need to look in the right places.
Thanks to Natalie Wolchover of Quanta Magazine for the report on the conference, I wish I could have been there.