Philosopher of science Bjørn Ekeberg, author of Metaphysical Experiments: Physics and the Invention of the Universe, reflects on recent discrepancies in the measurement of the universe’s expansion, the so-far-unsuccessful hunt for dark matter, and other research downers:
It’s perhaps worth stopping to ask why astrophysicists hypothesize dark matter to be everywhere in the universe? The answer lies in a peculiar feature of cosmological physics that is not often remarked. For a crucial function of theories such as dark matter, dark energy and inflation, which each in its own way is tied to the big bang paradigm, is not to describe known empirical phenomena but rather to maintain the mathematical coherence of the framework itself while accounting for discrepant observations. Fundamentally, they are names for something that must exist insofar as the framework is assumed to be universally valid.
Each new discrepancy between observation and theory can of course in and of itself be considered an exciting promise of more research, a progressive refinement toward the truth. But when it adds up, it could also suggest a more confounding problem that is not resolved by tweaking parameters or adding new variables. Bjørn Ekeberg, “Cosmology Has Some Big Problems” at Scientific American
Sometimes what we are looking for isn’t there because things don’t work the way we thought. Phlogiston and the ether are examples of that. They were reasonable ideas centuries ago but chemistry and physics don’t work the way proponents thought.
Are we there again?
The crux of today’s cosmological paradigm is that in order to maintain a mathematically unified theory valid for the entire universe, we must accept that 95 percent of our cosmos is furnished by completely unknown elements and forces for which we have no empirical evidence whatsoever. For a scientist to be confident of this picture requires an exceptional faith in the power of mathematical unification.
In the end, the conundrum for cosmology is its reliance on the framework as a necessary presupposition for conducting research. For lack of a clear alternative, as astrophysicist Disney also notes, it is in a sense stuck with the paradigm. It seems more pragmatic to add new theoretical floors than to rethink the fundamentals. Bjørn Ekeberg, “Cosmology Has Some Big Problems” at Scientific American
All that said, faith in mathematics is better than faith in a lucky rabbit’s foot because the mathematics might make sense someday.
Note: Sabine Hossenfelder seems to be writing along these lines in Lost in Math: How Beauty Leads Physics Astray.
See also: Rob Sheldon: Here’s why physicists are surprised by the universe’s increased expansion rate The two methods differ in that one is “direct” and the other “indirect”. Clearly one or both of them is making a mistake. Since it is hard to find (and people have looked) a reason why the direct method is failing, the feeling is that the indirect method must have a mistake in its model.
and
Discover: Even the best dark matter theories are crumbling