Science Seen Time One author Colin Gillespie helps you understand the physics of your world.
What’s Wrong with Relativity?
There is no absolute frame of reference. It’s called the Principle of Relativity. Problem is: The principle is wrong. How so?
Let’s take a closer look at what it is. Italian physicist Galileo Galilei had an idea. He said an experiment that’s done inside a smoothly moving ship can’t tell you that it’s moving. In 1905 Albert Einstein adopted this idea, turning it into ‘the principle of relativity (in the restricted sense).’ British physicist Sir Arthur Eddington—Einstein’s explainer-in-chief to the English-speaking world—had a now-widely-accepted way to state the principle: ‘It is impossible by any experiment to detect uniform motion relative to the ether.’ (The ether was the medium through which light waves were thought to travel.)
New theories and more recent measurements reveal that this is wrong.
(Einstein had a more cautious version. Rather than we can’t detect motion it said we don’t. And the principle should not be confused with his two theories of relativity.)
Cosmologists soon dumped Eddington’s principle. It led to conclusions that there is no preferred or absolute frame of reference; that we must mix space with time as spacetime; that there is no absolute way to determine the simultaneity of spatially separated events; and that there is no ether. In a cosmological view of the universe these conclusions are untenable. One way to think of this is: The entire universe provides a preferred or absolute frame of reference.
Here’s how we found this frame. Starting in the 1970s, measurements of the cosmic microwave background radiation or CMB gave us a window into it. Sorry, Sir Arthur: New measurements show with increasing precision our motion relative to the ether (thus achieving what Michelson and Morley set out to do with the wrong kind of instrument). They tell us we are moving at 365 km/s—more than 0.1 percent of light speed, toward speed—toward the constellation of Leo.
So, long said to be dead, the ether makes a big comeback in cosmology. This would have been no surprise to Einstein. In a 1920 lecture he explained how general relativity requires that the ether must be real and substantial, though its properties were not quite the same as people had imagined.
Some may argue that the CMB reflects only the part of the universe we see, which could be moving at a significant fraction of light speed relative to the perhaps-far-larger part of the universe that we can’t see. However, observing large-scale structure in the part we can see gives us reason to conclude this part moves little if at all. The movements of galaxies and larger structures that we see result from unbalanced forces of gravity. But these moving structures are far smaller than the visible universe, as one would expect due to both the long-range averaging and the inverse square law drop-off of gravitation at larger scales.
Of course, the CMB is not the ether. But it is observable. It is a good surrogate for the whole universe. This gives us a preferred or absolute frame of reference in principle, subject to a modest uncertainty (maybe 5 percent) in practice. It gives us absolute simultaneity. It fundamentally separates 3-D space from time and so abolishes the weird conundrums that come with the mathematical convenience of 4-D spacetime.
Meanwhile myths of relativity continue to both damage the fabric of physics and obstruct its progress. It’s easy to find both amateurs and serious physicists expounding with great certainty false propositions about relativity and ether Einstein laid to rest in 1920. As Wikipedia tells us: ‘Since the development of special relativity, theories using a substantial aether fell out of use in modern physics, and were replaced by more abstract models.’
Maybe this sounds like progress; but this is how faith in the Principle of Relativity has bad consequences. For example, it leaves faithful modern physicists searching their more abstract models for Dark Energy—which physics now knows holds two thirds of the universe’s mass—long after Einstein left his substantial ether right under their noses.
This too tells us that the Principle is wrong! It’s true that local ether provides no absolute frame of reference. But the whole universe—most of which is ether—does.
Sir Arthur Eddington (1920), Space, Time & Gravitation: An Outline of the General Relativity Theory, Cambridge: Cambridge University Press, p. 20.
Wikipedia, “Aether theories”, citing Max Born, https://en.wikipedia.org/wiki/Aether_theories
Image credit: AKG; https://www.mpg.de/9236014/eddington-sonnenfinsternis-1919