As a science communicator, there are certain emails I have come to expect. By and large, the most common of these emails are the, “Hi, I need help with my math, but I have a solid explanation for why relativity is wrong, and I just need you to do the math for me” emails.

First of all, I have no idea what I have done that would ever make someone think I’m willing to do theoretical physics as a favor for them. Second, relativity is true, and while it has some not well-defined corners, the parts of it that we have worked out have been proven over and over and over through myriad experiments.

One of the best laboratories is naturally occurring. Sixteen years ago, astronomers discovered a pair of pulsars in a binary system. These fast-rotating stars are like cosmic metronomes, with one flashing the beat every 44 seconds while the other does so every 2.8 seconds. While the stars themselves, in their pockets of time and space, are the most perfect metronomes in the universe, what we see is affected by the distortions of relativity. A quick glance may not reveal these effects, but over the past sixteen years those distortions have added up to yet more definitive proof that Einstein was right.

Over the years, researchers have been able to watch the elliptical orbits rotate so that the long axis of the orbit changes its alignment. What they see matches relativity perfectly, in all its finest details. They can also see the orbits shrinking as they radiate away energy in the form of gravitational waves. 

And here’s the thing: since energy and mass are the same things, this lost energy is no different than lost mass. This is the first system that can be measured so precisely that this matters. This system has a lot of firsts. The effects of frame dragging actually make it possible to figure out the radius of the faster of the two pulsars, and that radius is just 22 kilometers or almost 14 miles.

One set of maths – general relativity – is able to completely and consistently explain this system. Nothing else can do it. General relativity is true. So please, stop emailing me your alternatives and asking me to do your maths. Einstein was right, and the Universe has complex order we need to savor.

This work was led by Matt Kramer and appears in a pair of papers in Physical Review X.

More Information

MPIFR press release

The only known pulsar duo sheds new light on general relativity and more (Science News)

“Strong-Field Gravity Tests with the Double Pulsar,” M. Kramer et al., 2021 December 13, Physical Review X