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      Hello, and welcome to November’s Lost in Space-Time, the monthly physics newsletter that unpicks the fabric of the universe and attempts to stitch it back together in a slightly different way. To receive this free, monthly newsletter in your inbox, sign up here.

                                 Einstein’s forgotten twisted universe

           There’s a kind of inevitability about the fact that, if you write a regular newsletter about fundamental physics, you’ll regularly find yourself banging on about Albert Einstein. As much as it comes with the job, I also make no apology for it: he is a towering figure in the history of not just fundamental physics, but science generally.

            A point that historians of science sometimes make about his most monumental achievement, the general theory of relativity, is that, pretty much uniquely, it was a theory that didn’t have to be. When you look at the origins of something like Charles Darwin’s theory of evolution by natural selection, for example – not to diminish his magisterial accomplishment in any way – you’ll find that other people had been scratching around similar ideas surrounding the origin and change of species for some time as a response to the burgeoning fossil record, among other discoveries.

             Even Einstein’s special relativity, the precursor to general relativity that first introduced the idea of warping space and time, responded to a clear need (first distinctly identified with the advent of James Clerk Maxwell’s laws of electromagnetism in the 1860s) to explain why the speed of light appeared to be an absolute constant.

             When Einstein presented general relativity to the world in 1915, there was nothing like that. We had a perfectly good working theory of gravity, the one developed by Isaac Newton more than two centuries earlier. True, there was a tiny problem in that it couldn’t explain some small wobbles in the orbit of Mercury, but they weren’t of the size that demanded we tear up our whole understanding of space, time, matter and the relationship between them. But pretty much everything we know (and don’t know) about the wider universe today stems from general relativity: the expanding big bang universe and the standard model of cosmology, dark matter and energy, black holes, gravitational waves, you name it.

              So why am I banging on about this? Principally because, boy, do we need a new idea in cosmology now – and in a weird twist of history, it might just be Einstein who supplies it. I’m talking about an intriguing feature by astrophysicist Paul M. Sutter in the magazine last month  It deals with perhaps general relativity’s greatest (perceived, at least) weakness – the way it doesn’t mesh with other bits of physics, which are all explained by quantum theory these days. The mismatch exercised Einstein a great deal, and he spent much of his later years engaged in a fruitless quest to unify all the physics.