Generally relativehttps://indianexpress.com/article/opinion/editorials/generally-relative/

Generally relative

Ten equations to rule them all turn 100, and they are still the masters of the universe.

A century ago this week, 32 announced the general theory of relativity to the Prussian Academy of Sciences. Ten years earlier, in what has come to be known as his annus mirabilis, he had found the answer to the eternal question about life, the universe and everything except acceleration due to gravity. That was the special theory of relativity, and it had delighted a world tiring of the certainties of 19th-century Europe by suggesting that it all depends. What time is it? It depends on the speed at which you are travelling. The faster you go, the slower time passes. This is not an illusion.

Actually, it all depends on the speed at which your frame of reference is travelling. Now, what is that? Is it the bicycle you’re riding, say, or the planet that the bicycle is traversing, or the solar system, or the galaxy, or the universe? If we live in a multiverse, our universe can be read as just one inertial frame of reference among many, all in relative motion. In special relativity, the only constant is the speed of light in a vacuum. Isaac Newton, Albert Einstein and Ramar Pillai would report it identically, though Pillai might tack on some extravagant claims.

Special relativity was all about speed. It took Einstein the decade from 1905 to 1915 to address acceleration, particularly the acceleration due to gravity. Quantified by Newton three centuries ago, general relativity read gravity as what is experienced when mass rumples the space-time continuum. General relativity is delightfully bendy. The very fabric of the universe it lays out bends. Space-time bends. Light bends. Stubbornly, forks and spoons do not bend. Nor do the fundamental laws of physics. In this universe, Uri Geller is still a charlatan, and so is Ramar Pillai.