Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Thursday, June 22, 2023

A new field

I was fortunate enough that the day-job of my bandmate of many years, Kathy Selby, was working as a physicist at Cornell University.

As you might suspect, our conversations while traveling to gigs were pretty interesting.

One time we were on our way to play for a dance in Rochester, and I asked her what she thought about dark matter and dark energy -- which according to current models make up, respectively, 27% and 68% of the mass-energy content of the universe.  [Nota bene: the use of the word "dark" in both names does not mean that they are in any sense the same thing.  Dark matter is a name for the observation that the gravitational attraction of conventional matter is insufficient to account for the measured velocities of galaxies and galaxy clusters; there must be some other, unseen matter there that does not interact with ordinary matter electromagnetically, or else our model for gravity is incorrect.  Dark energy, on the other hand, is a theoretical energy inherent in space itself that might explain the accelerating expansion of the universe.]

So yes, only five percent of the universe is the regular stuff we see around us on a daily basis.  The other 95% is largely unexplained, and is yet to be detected directly.

In any case, I asked Kathy what her opinion was about the rather uncomfortable situation of having the vast majority of the universe thus far inaccessible to scientific study.

"In my opinion," she said, "we're in a situation a bit like physicists were in the late nineteenth century.  They knew light had strange properties.  It acted like a wave much of the time, so they'd postulated a medium -- the luminiferous aether -- through which the wave was propagating.  The problem was, every attempt to detect the aether failed.  Then Michelson and Morley came along and showed that the prediction of an 'aether drag' caused by the motion of the Earth through space didn't exist, suggesting very much that the aether didn't either.  The speed of light in a vacuum seemed to be the same in all reference frames, which was unlike any other wave ever studied.  Then Einstein said, 'Well, let's start by assuming that the speed of light in a vacuum is the same regardless of your reference frame, and see what happens,' and the aether became unnecessary.  Of course, what came out of that shift in perspective was the Theories of Relativity.

"What I think," she concluded, "is that we're waiting for this century's Einstein to tell us that we've been looking at everything the wrong way -- and suddenly the problems of dark matter and dark energy will evaporate, just like the aether did."

Well, we may have just gotten a glimpse at one possibility for that shift in perspective, courtesy of physicist Lucas Lombriser of the Université de Genève.

A paper published two weeks ago in the journal Classical and Quantum Gravity started by looking at what has been called "the worst prediction in physics" -- the value of the cosmological constant, which sets the expansion rate of the universe.  The prediction by theoretical physicists of what the cosmological constant should be given what we know about matter, and what we actually measure it to be, differ by 120 orders of magnitude -- that's 1 followed by 120 zeroes.

Oops.  Major oops.  This is what gave rise to the mysterious dark energy, some peculiar property of space itself that solves the mismatch.  But as far as what exactly this dark energy might be, physicists have come up empty-handed, so more and more it's seemed like a placeholder to cover up for the fact that we don't really understand what's going on.

This, Lombriser says, is because -- like with Einstein's solution to the aether -- we're starting out with the wrong assumption.

Maybe the universe is flat and static, as Einstein himself believed (after the discovery of red shift and the expansion of the universe, Einstein was forced unwillingly to accept an expanding universe and a cosmological constant -- which he later called "the greatest blunder of my career").  Perhaps space isn't expanding; it's the masses of particles that have changed over time.  The altered masses change the gravitational field that permeates space, and that's what generates red shift and the appearance of expansion.  So there is a cosmological constant, but it comes from the particles themselves, and the field in which they reside, evolving.

[Image licensed under the Creative Commons Original image by User:Vlad2i, slightly modified by User:mapos., Gravitational red-shifting2, CC BY-SA 3.0]

This new take solves three problems at once.  It does away with the cosmological constant mismatch; dark energy pretty much disappears completely; and the field itself that's responsible for the mass change could account for dark matter, as it shares many properties with an axion field, and axions are one of the leading candidates for the constituents of dark matter.  

This simultaneous solution of three vexing problems is certainly intriguing.  But the question is, is Lombriser right?  "The paper is pretty interesting, and it provides an unusual outcome for multiple problems in cosmology," said physicist Luz Ángela García, of the Universidad ECCI Bogotá, who was not involved in the research.  "The theory provides an outlet for the current tensions in cosmology.  However, we must be cautious.  Lombriser's solution contains elements in its theoretical model that likely can't be tested observationally, at least in the near future."

Which, of course, is the issue, and is all too common in this branch of science.  Even though Einstein's Theories of Relativity did a good job of accounting for various anomalies in the properties of light, the first precise confirmation of his predictions didn't occur until 39 years after he wrote his seminal paper in 1915.  How to detect the fluctuating field Lombriser postulates -- and, more importantly, how to distinguish its effects from the current model of expanding space -- is currently beyond us.

So maybe Lombriser is what my bandmate Kathy called "this century's Einstein."  Or maybe his ideas will prove to be just another unverified or (worse) unverifiable hypothesis.  But I have to say, when I read about what he's proposing, my ears did perk up.  It has the feel of a paradigm shift -- just what we've been waiting for.

And you can bet that the physicists are going to be all over this, looking for ways either to confirm or refute what he's saying.


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