The field of physics may be turned on its head soon, said renowned physicist Nima Arkani-Hamed during a live lecture from the Perimeter Institute for Theoretical Physics in Waterloo, Canada.
For one, he said, the tried and true physics of relativity and quantum mechanics don't get along well. The problem is that in some sense, the principles behind these theories seem to be impossible when physicists dig a little deeper into them, Arkani-Hamed said. Scientists run into a lot of problems when they try to apply these theories to the entirety of space and time.
The two ideas are also incredibly constraining, and they make it challenging for physicists to think outside the box and develop new ideas and theories, Arkani-Hamed said. [The 9 Biggest Unsolved Mysteries in Physics]
"It's almost impossible to monkey around with the rules and not be wrong immediately," Arkani-Hamed said.
Physicists have known about this disparity for a while, but progress on fundamental questions in physics takes a long time. Scientists proposed the existence of the Higgs boson particle, for example, decades before it was actually discovered.
An unexplained macroscopic universe
One problem is that conventional physics doesn't really account for why the universe is so large, Arkani-Hamed said.
Albert Einstein's theory of relativity showed that a huge amount of energy exists in the vacuum of space, and it should curve space and time. In fact, there should be so much curvature that the universe is a tiny, crumpled ball.
"That should make the universe horrendously different than what it is," Arkani-Hamed said.
But quantum mechanics also poses a problem. The theory is good at describing the very small realm of particle physics, but it breaks down when physicists try to apply it to the universe as a whole.
"Everything that quantum mechanics is, is violated by our universe because we're accelerating (referring to the idea that the universe is expanding) – we don't know what the rules are," Arkani-Hamed said. "When you try to apply quantum mechanics to the entire universe, quantum mechanics cries 'uncle.'"
Physics frontiers
One possible way to solve the problem is with an entirely new theory beyond the Standard Model, the reigning theory of particle physics, the physicist said. [Sparticles to Neutrinos: The Coolest Little Particles in the Universe]
One idea is called string theory, which proposes that particles aren't actually fundamentally particles. Instead, the particles and all the matter in the universe they make up are composed of tiny, vibrating strings. The equations that support string theory appear to work, but that doesn't mean there are no other viable formulas or explanations, Arkani-Hamed said.
Supersymmetry is another possible "new physics" explanation. Under this idea, all subatomic particles have a "superpartner" particle that physicists have yet to discover. Supersymmetry would also open up extra directions that the particles can move in. The discovery of supersymmetry would bolster the Standard Model of physics, scientists have said.
"It's the last thing nature can do to make itself compatible with the general principles of physics that already exist," Arkani-Hamed said.
When the world's largest atom smasher, the Large Hadron Collider (LHC), is up and running again next year, physicists will be looking for the extra particles that supersymmetry suggests should exist.
Either way, after a year or two of running the LHC, the question of whether supersymmetry exists should be answered, Arkani-Hamed said.
The experiments over the next few years will likely tell physicists if they need to fine-tune existing theories or if the field of physics is due for a much deeper and more dramatic paradigm shift.
The questions on the table now are the underpinnings of space and time, and the origin and fate of the universe, Arkani-Hamed said.
"Today we finally have the theoretical framework in place to ask these kinds of big questions," Arkani-Hamed said. "The next step will likely be a revolution."
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