To understand these mind-bending theories, you’ll need to kiss Newton’s apple goodbye.
- Physicists say that understanding gravity requires a quantum mechanical explanation.
- But no direct evidence of hypothetical quantum gravity particles, called gravitons, exists.
- Experimenters hope to find the effects of gravitons within ten years.
As far as we know, our physical world is governed by four fundamental forces: electromagnetism, weak and strong nuclear forces, and gravity. Apart from playing with bar magnets or marveling at the light of a rainbow, it’s gravity that we’re most familiar with here on Earth. Yet, it’s actually the least understood force of the bunch.
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Our understanding of gravity has undergone a number of face lifts in the past several hundred years—from Newton’s take on the movements of planets and apples to Einstein’s theory of general relativity and spacetime. However, for physicists like Kathryn Zurek, a theoretical physics professor at Caltech whose work focuses on dark matter as well as observational signals of quantum gravity, that still isn’t good enough.
She’s not the only one. Theorists and experimentalists around the world have toiled for decades to compose a so-called “theory of everything” that would unite quantum explanations of the very small with the classical physics of the very large (such as humans and planets). A verifiable theory of quantum gravity is at the center of this quest to offer a single theory that explains everything in our universe.
“For many reasons, we believe that the fundamental understanding of gravity needs to be quantum mechanical in nature,” Zurek tells Popular Mechanics. “So we need to figure out how to make these foundational principles of quantum mechanics [work for] gravity. That is quantum gravity—it’s classical gravity, which has been quantum mechanically proved.”