Friday, October 25, 2013

5 Unanswered Questions That Will Keep Physicists Awake at Night

Orion Nebula photo 

Physics is all about probing the most fundamental mysteries in nature, so it’s no surprise that physicists have some very basic questions about the universe on their minds. Recently, Symmetry Magazine (published by two U.S.-government funded physics labs) asked a group of particle physicists to name the open questions in physics they most want answers to. Here’s a sample of the quandaries they shared:

“What will be the fate of our universe?”

The poet Robert Frost famously asked whether the world would end in fire or ice, and physicists still can’t answer the question. The future of the universe—the question named by Steve Wimpenny of the University of California, Riverside—largely depends on dark energy, which at this point is an unknown entity. Dark energy is responsible for the accelerating expansion of the universe, but its origins are entirely mysterious. If dark energy is constant over time, we’re likely looking at a “big freeze” in the future, at which point the universe continues to expand faster and faster, and eventually galaxies are so spread out from each other that space seems like a vast wasteland. If dark energy increases, this expansion could be even more severe, so that not just the space between galaxies but the space within them expands, and galaxies themselves are ripped apart—a fate dubbed the “big rip.” Another option is that dark energy decreases so that it cannot counteract the inward-pulling force of gravity, causing the universe to fall back in on itself in a “big crunch.” So basically, whichever way it goes, we’re doomed. On the bright side, none of these eventualities should come to pass for billions or trillions of years—plenty of time to decide if we’re hoping for fire or ice.

“The Higgs boson makes absolutely no sense. Why does it exist?”

The tone of this question was tongue in cheek, says its asker, Richard Ruiz of the University of Pittsburgh, but it points to a very real lack of understanding about the nature of the particle famously discovered last year at the Large Hadron Collider (LHC) in Europe. The Higgs boson helps explain how all other particles got their mass, yet it raises many other questions. For example, why does the Higgs boson interact with each particle differently—the top quark interacts much more strongly with the Higgs than the electron does, giving the top quark a much greater mass than the electron. “This is the only example of a ‘non-universal’ force in the Standard Model,” Ruiz says. Furthermore, the Higgs boson is the first fundamental particle found in nature with zero spin. “This is an entirely new sector in Standard Model particle physics,” Ruiz says. “How it comes about, we have no idea.”
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