Dan Harlow spends a lot of time thinking in a “boomerang” universe.
The MIT physicist is searching for answers to one of the biggest questions in modern physics: How can our universe abide by two incompatible rulebooks?
Both theories do remarkably well in their respective lanes. However, Einstein’s theory breaks down when trying to describe how gravity works at quantum scales, while quantum mechanics makes reality-bending predictions when applied at massive, cosmic dimensions. For over a century, physicists have searched for ways to unite the two theories and get to the truth of what makes our universe tick.
Harlow suspects that any connecting thread may be too delicate to grasp in our existing universe. Instead, he’s looking for answers in a “boomerang” version — an alternate reality that folds back on itself, much like a boomerang’s trajectory, rather than stretching and expanding without end as our actual universe does. Quantum gravity in this boomerang universe turns out to be easier to understand, as it can be reformulated in terms of conventional quantum theory (without gravity) using a powerful idea called holographic duality. This makes it far simpler to contemplate, at least from a theory perspective.
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