Laws of physics still universal, studies find


Two independent approaches to testing a fundamental prediction of relativity confirm Einstein was on the money. Andrew P Street reports.


Mirrors on the moon have helped confirm a fundamental prediction of relativity.
Mirrors on the moon have helped confirm a fundamental prediction of relativity.
Viviana Gonzalez / Getty Images

Sure, the mainstream media might like to trumpet results that appear to challenge Einstein and threaten to turn everything we know about physics on its head, but those results almost always turn out to be wrong. So, it’s genuinely reassuring when another experiment that appears to confirm our most basic assumptions about the way the cosmos operates.

One of the most fundamental ideas about our universe is that the laws of physics apply across the board – gravity in a distant galaxy behaves like it does in this one, for example. A more elegant piece of theory is what’s called Lorentz invariance - named for Hendrick Lorentz, the scientist who first derived it from his equations teasing out Einstein’s work on special relativity.

Lorentz Invariance states that the laws of physics remain constant for all observers within the same inertial frame. It’s not an idea which is uncritically accepted, since there are mathematical models that predict this symmetry will break down when attempting to reconcile relativity and particle physics. However, two new papers in the journal Physical Review Letters suggest that – for now at least – Lorentz invariance still holds.

Both pieces of research look at the effects of gravitational interactions, but take very different routes. The first, from a team led by Adrien Bourgoin of the Universite de Caen Normandie in France, used almost half a century of data from lasers bounced off mirrors placed on the moon’s surface by the Apollo missions to record the orbital and rotational motion.

The data constituted the first direct experimental simultaneous measurement of Lorentz symmetry in two linked fields of physics: the pure gravitational sector and the classical point-mass limit of the matter sector. The team found no deviation from the predictions of general relativity.

The second paper covered research led by Jay Tasson from Carleton College in Minnesota, US, and used data from superconducting gravimeters, exquisitely sensitive accelerometers which measure the local gravitational field using a niobium sphere suspended in a magnetic field, supercooled by liquid nitrogen.

The research failed to find any Lorentz violations – a good thing, all told – but did so by achieving measurements 10 times more accurate that previous gravimeter experiments.

Both concluded that there was no sign of Lorentz symmetry violation to a far greater degree of precision than had previously been attained. Of course, this doesn’t prove that Lorentz invariance cannot be broken, but we now have a much clearer idea of the range in which it definitely holds.

In other words: the universe is still behaving as we expect. In these volatile times, that’s a relief.

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Andrew P Street is a widely published journalist, non-fiction author and former columnist for the Sydney Morning Herald.
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