Tossing overboard the assumptions about our universe? Rob Sheldon responds

Here’s an especially hyperactive science media release, “Should the measured values be confirmed, this would toss many assumptions about the properties of the universe overboard. Note, not just “rethought” but tossed overboard.

No matter where we look, the same rules apply everywhere in space: countless calculations of astrophysics are based on this basic principle. A recent study by the Universities of Bonn and Harvard, however, has thrown this principle into question. Should the measured values be confirmed, this would toss many assumptions about the properties of the universe overboard. The results are published in the journal Astronomy & Astrophysics, but are already available online.

Since the big bang, the universe has swollen like a freshly formed raisin roll put in a warm place to rise. Until recently, it was thought that this increase in size was occurring evenly in all directions, as with a good yeast dough. Astrophysicists call this “isotropy.” Many calculations on the fundamental properties of the universe are based on this assumption. It is possible that they are all wrong — or at least, inaccurate — thanks to compelling observations and analyses of the scientists from the Universities of Bonn and Harvard.

For they have put the isotropy hypothesis to the test for the first time with a new method that allows more reliable statements than before. With an unexpected result: According to this method, some areas in space expand faster than they should, while others expand more slowly than expected. “In any case, this conclusion is suggested by our measurements,” states Konstantinos Migkas, from the Argelander Institute for Astronomy at the University of Bonn.

University of Bonn, “Doubts about basic assumption for the universe” at ScienceDaily

Paper. (open access)

Our physics color commentator Rob Sheldon offers some thoughts below:

Just a few quick observations on this news item:

1) Isotropy is the assumption that there are no processes in the universe that show a preferred direction, or, that all such processes that show a preferred direction are thoroughly mixed and we cannot observe them.

For example, the people in a crowd have eyes on the front of them which is a preferred direction. If we demand isotropy, then when we take a drone picture of a big crowd, there should be just as many looking east as west, north, or south. There’s no preferred direction, unless of course, we’re photographing a rock concert. So the demand for isotropy is less a statement about the laws of physics, as it is a statement about the necessity of randomness.

Then the results of this galaxy survey have probably very little to do with the “laws of physics” and everything to do with “the assumption of isotropy”.

Then the results of this galaxy survey have probably very little to do with the “laws of physics” and everything to do with “the assumption of isotropy”.

The reason that physicists have assumed isotropy, is that in the past they didn’t have the mathematical tools to assume anything else. That is, we can simulate a supernovae as a 1D radial expansion if we assume isotropy, but we would have to do a full 3D simulation if we allowed anisotropy (non-isotropy). When supercomputers became available about 20 years ago, we could do supernovae calculations in 3D and lo-and-behold, the results were vastly different from the 1D isotropy calculations. The reason was simple–there were “modes” of the explosion which could not be reduced to 1D, so suppressing these modes by enforcing isotropy changed the simulation of the explosion.

So why have cosmologists not done the same thing in their Big Bang models, why have they not done them in 3D?

That’s a really good question. My guess is that the 1D results were so good, they turned their bug into a feature; they now think that isotropy is DEMANDED by the physics. One argument might go like this: “Isotropy is the condition of maximum entropy, so to use a 3D simulation would be akin to allowing the Big Bang to contain information, to be designed. And we can’t allow that.”

I don’t have any papers that use those words, but this is the sort of metaphysical argument which is employed to defend the isotropy mandate. Which may explain why the author of this article wrongly thinks that mandating isotropy is the reasonable demand for physics to be the same everywhere.

There are many physical processes that are not isotropic. The first, and most important one that comes to mind, is magnetic fields. You’ve all seen the picture of a horseshoe magnet under a piece of paper sprinkled with iron filings. The filings all line up in lines. These “magnetic field lines” have become a staple of physics text books from elementary through graduate school. Somewhere in graduate school you are told that it is a mental picture only, and real B-fields

are not lines at all, but the curl of a “vector potential” and the Aharonov-Bohm experiment is then described. But we all still believe in those strands of spaghetti, which look different when viewed end-on than perpendicularly. Electrons also see them differently, because they can cruise along the spaghetti like it was a copper wire, but find it very difficult to move perpendicular to the B-field. So if the universe began with a magnetic field, one would EXPECT there to be a difference in some direction or other. Which is why I’m working on a Magnetic Big Bang Nucleosynthesis model.

But really, there is an even easier explanation for anisotropy. If we are moving through an isotropic background of galaxies, then the ones in front of us are blue-shifted and the ones behind us are red-shifted. This creates a “dipole” pattern in the cosmic microwave background radiation (CMBR) among others, which has been observed for 60 years.

So why is this given a short shrift at the end of the article? Subir Sarkar, in his 40 minute interview with Sabine Hossenfelder, explained why. Because it has been done incorrectly for the past 50 years. The assumption was that us (the Milky Way) and our associated group of galaxies (Andromeda, etc), are all moving with respect to the isotropic background galaxies, so that if we draw a sphere of about 100 Megaparsecs around us, everything outside that sphere is stationary. Sarkar says the correct number is much closer to 250 Mpc, which means what we took as stationary isn’t really stationary.

Now comes the humorous part. Astronomers “correct” for the local motion (shifting the blue side down and the red side up) but if they use the wrong model, they “over-correct” and create distortions that aren’t in the original data. All that theorizing then, is based on distortions of the data created by applying the wrong correction! Sarkar complains that if astronomers would only be honest and store the uncorrected data rather than the wrongly-corrected data, he could do his fits with 10,000’s of data points instead of 100’s.

Therefore the problem with this analysis of X-rays from galaxies, is that they think the galaxies are stationary when they aren’t. Hence the result that they appear to be moving could very well be the same problem Sarkar discusses, which is that over-corrected data is being used in the fits.

Since no one discusses the result as a potentially embarrassing over-correction, naturally the whole local-motion discussion is given short shrift. Just another example of the hubris that lies at the foundation of scientism and seems to especially infect cosmology.

Rob Sheldon is the author of The Long Ascent, Vol. 1 and The Long Ascent, Vol. 2.