New estimate for Hubble constant differs from previous and also conflicting results
The uncertainty of science: Using microlensing effects scientists have measured a new estimate for the Hubble constant, the rate in which the universe is expanding, and have come up with a number that is different from previous results.
Using adaptive optics technology on the W.M. Keck telescopes in Hawaii, they arrived at an estimate of 76.8 kilometers per second per megaparsec. As a parsec is a bit over 30 trillion kilometers and a megaparsec is a million parsecs, that is an excruciatingly precise measurement. In 2017, the H0LICOW team published an estimate of 71.9, using the same method and data from the Hubble Space Telescope.
The new SHARP/H0LICOW estimates are comparable to that by a team led by Adam Reiss of Johns Hopkins University, 74.03, using measurements of a set of variable stars called the Cepheids. But it’s quite a lot different from estimates of the Hubble constant from an entirely different technique based on the cosmic microwave background. That method, based on the afterglow of the Big Bang, gives a Hubble constant of 67.4, assuming the standard cosmological model of the universe is correct.
An estimate by Wendy Freedman and colleagues at the University of Chicago comes close to bridging the gap, with a Hubble constant of 69.8 based on the luminosity of distant red giant stars and supernovae.
So five different teams have come up with five different numbers, ranging from 67.4 to 76.8 kilometers per second per megaparsec. Based on the present understanding of cosmology, however, the range should have been far less. By now the physicists had expected these different results to be close to the same. The differences suggest that either their theories are wrong, or their methods of measurement are incorrect.
The most likely explanation is that we presently have too little knowledge about the early universe to form any solid theories. These measurements are based on a very tiny amount of data that also require a lot of assumptions.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The uncertainty of science: Using microlensing effects scientists have measured a new estimate for the Hubble constant, the rate in which the universe is expanding, and have come up with a number that is different from previous results.
Using adaptive optics technology on the W.M. Keck telescopes in Hawaii, they arrived at an estimate of 76.8 kilometers per second per megaparsec. As a parsec is a bit over 30 trillion kilometers and a megaparsec is a million parsecs, that is an excruciatingly precise measurement. In 2017, the H0LICOW team published an estimate of 71.9, using the same method and data from the Hubble Space Telescope.
The new SHARP/H0LICOW estimates are comparable to that by a team led by Adam Reiss of Johns Hopkins University, 74.03, using measurements of a set of variable stars called the Cepheids. But it’s quite a lot different from estimates of the Hubble constant from an entirely different technique based on the cosmic microwave background. That method, based on the afterglow of the Big Bang, gives a Hubble constant of 67.4, assuming the standard cosmological model of the universe is correct.
An estimate by Wendy Freedman and colleagues at the University of Chicago comes close to bridging the gap, with a Hubble constant of 69.8 based on the luminosity of distant red giant stars and supernovae.
So five different teams have come up with five different numbers, ranging from 67.4 to 76.8 kilometers per second per megaparsec. Based on the present understanding of cosmology, however, the range should have been far less. By now the physicists had expected these different results to be close to the same. The differences suggest that either their theories are wrong, or their methods of measurement are incorrect.
The most likely explanation is that we presently have too little knowledge about the early universe to form any solid theories. These measurements are based on a very tiny amount of data that also require a lot of assumptions.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
You know, I can’t get terribly excited over a 10% disagreement; I’m old enough to remember when it was war to the death over 50 km/s/Mpc vs. 100 km/s/Mpc.
Hmmm, so the Hubble Constant isn’t…..
Those who truly understand the propagation of error and significant figures are with Call Me Ishmael.
I could give many examples but have done that before here.
The biggest discrepancies (and they seem not that great) are between methods that use the “cosmic microwave background-early cosmic history” theories whose ABSOLUTE accuracy is easily questionable, and those methods using more direct measurements. When error bars are taken into consideration, the consistency of the latter methods is remarkable. Rather than saying the theories are “wrong”, it is amazing how “right” they seem to be.
Most theories or models (perhaps all) and all experiments AND their error bars are not ABSOLUTELY exact (ie “wrong”)…That is not a useful question; the question is how useful are they.
A nice review of methods/results is given here:
https://en.wikipedia.org/wiki/Hubble%27s_law#Measured_values_of_the_Hubble_constant
The Cosmic Distance Ladder and the Hubble Controversy.
Dr. Laird Whitehill Fun with Astronomy
https://youtu.be/A_XW-cMgfgc
54:15
“There is stuff we didn’t know that we didn’t know. Now we know what we don’t know. And we don’t understand it. Why do different researchers get different results about the expansion rate of the Universe (the Hubble Constant). By now we have to admit that both groups are right. So something is wrong, not with their conclusions, but with our understanding of the universe.”