In its waning years Albert Einstein spent his time tilting windmills, trying to unite all the forces of nature. He died disappointed, and his attempt would go down in history as his greatest failure.
But Einstein’s failed dream could eventually become his ultimate triumph if a small group of theoretical physicists rework his old ideas. It will not necessarily bring together all the forces of the universe, but it could explain some of the most pressing issues facing modern science.
Einstein is not enough
The most successful theory of gravity known to mankind is Einstein’s famous general theory of relativity. Einstein spent more than seven years developing it, and it was worth the wait. On the surface, the general theory of relativity is deceptively simple. All the drama of the universe takes place on the grand, fourth-dimensional stage that is mentioned space time. Matter and energy – the actors and actresses of the cosmos – run around doing their thing, saying their way. Matter and energy distort space-time, causing it to warp and warp. That warping, in turn, tells matter and energy how to move and behave.
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And voila: general relativity! The constant dialogue between space-time stage and matter and energy is what we think of as gravity.
Einstein’s theory has passed every observational test, which is why it has survived the century since her birth. It has predicted and explained strange phenomena in the universe, including the bending of light around massive objects and the formation of black holes.
And yet we know it’s broken. While general relativity says black holes should exist, it breaks down completely when it tries to describe their singular heart. We have no description of gravity on such a subatomic scale on which quantum mechanics predominates. On this scale, when gravity gets both strong and short, general relativity can’t even make predictions – the math just falls apart.
Those are places where we know that general relativity is breaking down. But aside from that, astronomers have noticed two phenomena that are also not fully explained by general relativity: most of the matter in the universe (the so-called dark matter) does not interact with light; and the expansion of the universe is accelerating every day (thought to be caused by as yet unknown dark energy). To explain dark matter and dark energy, we have two choices. Either the general theory of relativity is perfectly correct, but our cosmos is filled with strange new substances, or the general theory of relativity is downright wrong.
Do the twist
Einstein himself tried to push the boundaries of general relativity. But he was not motivated by the puzzles of black hole singularities or an accelerating universe – no one knew they existed, let alone major theoretical challenges.
Instead, Einstein was motivated by a higher purpose: an attempt to unify all (known) laws of nature in a single mathematical framework. In his case, he had gravity on the one hand, represented by his now famous general theory of relativity, and electromagnetism on the other hand, represented by Maxwell’s equations which described everything from magnets and electric currents to relieve themselves.
In his attempts to make everything into a super theory, Einstein introduced general relativity 2.0. The basic version of relativity only cares about the curvature of space-time. But when restarting Einstein, attention was also paid to the twist or torsion of space-time. There was no need to include torsion in his original theory, as it turned out that you only needed curvature to explain gravity. But now that Einstein was trying to explain more than gravity, he had to add extra effects.
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Einstein had hoped that the distortions of space-time would somehow be related to electromagnetism (in the same way that the curvature of space-time is connected to gravity), but unfortunately he could not find solutions and his new one died. theory with him.
But other physicists have never given up on the dream and have tried to unite physics ever since. One of the best developed concepts is called string theory, which claims that all particles are really tiny vibrating strings. Oh, and our universe has extra spatial dimensions that are all small and rolled up.
String theory was never based on Einstein’s original idea of the twist of space-time, but now physicists are giving that old idea, called telparallel gravity, a second look.
Working in parallel
The name “teleparallel” comes from Einstein’s original work that explored the nature of distant parallel lines in its geometric framework and how both the curvature and the curvature of space-time affected the motion of matter and energy. Physicists today don’t think teleparallel gravity can unify physics (even Einstein eventually gave up on the idea), but it could be an interesting candidate for a new theory of gravity.
That’s because theorists have used teleparallel gravity to explain things like the accelerated expansion of the universe, the early post-era period. Big Bang when the universe took off, called “inflation” and more recent problems such as a perceived conflict between different measures of the cosmos’ expansion rate. In other words, teleparallel gravity has turned out to be quite predictive.
But what about those early dreams of a unified theory? Teleparallel gravity may be an interesting and useful new approach to gravity, but it doesn’t get us any closer to understanding a more fundamental law of physics. Instead, physicists have used the language of string theory to do that work, so the question naturally arose: Does string theory – which claims to be the ultimate theory of everything – relate in any way to teleparallel gravity? In other words, if teleparallel gravity can possibly solve all these annoying problems like dark matter and dark energy, does it flow as a natural consequence of string theory, or are these two separate lines that don’t have any connection to each other?
Recently, theoretical theorists have begun to link telparallel gravity with string theory, which provides motivation for the theory within the fibrous universe, as reported in a paper in the preprint journal arXiv in November. In their work they showed how telparallel gravity can be a consequence of string theory. This is an important insight, because string theory should be able to explain all the laws of physics, and if teleparallel gravity is a better version of general relativity, and turns out to be correct, then you should be able to deduce telparallelism from the mathematics of string theory.
Here’s an analogy. Suppose the police identify a murder weapon at a crime scene (general relativity). They have a prime suspect (string theory) that they want to connect to the murder weapon. But new crime scene analysis reveals that a different weapon (telparallelism) triggered the murder. Could the prime suspect still be linked to the new murder weapon?
The short answer is yes.
There is still a lot of work to be done. String theory is not finished yet (and may never be, if we never come up with hard mathematical solutions), so any connection it can make to reality is helpful. If teleparallel gravity proves to be a useful way of explaining some of the current shortcomings of general relativity, and we can deduce telparallelism from string theory, then that is another step towards realizing Einstein’s ultimate dream of unification – not like him. envisioned it, but it still counts.
Originally published on Live Science.