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Why String Theory Still Offers Hope We Can Unify Physics | Brian Greene

Why String Theory Still Offers Hope We Can Unify Physics Science Smithsonian


This spring, after nearly two years of upgrades, the Large Hadron Collider will crackle back to life, smashing protons together with almost twice the energy achieved in its previous runs. Sifting through the debris with the most complex detectors ever built, researchers will be looking for evidence of anything that doesn’t fit within the battle-tested “Standard Model of particle physics,” whose final prediction, the Higgs boson, was confirmed just before the machine went on hiatus. While it is likely that the revamped machine is still far too weak to see strings themselves, it could provide clues pointing in the direction of string theory. 

Many researchers have pinned their hopes on finding a new class of so-called “supersymmetric” particles that emerge from string theory’s highly ordered mathematical equations. Other collider signals could show hints of extra-spatial dimensions, or even evidence of microscopic black holes, a possibility that arises from string theory’s exotic treatment of gravity on tiny distance scales.

While none of these predictions can properly be called a smoking gun—various non-stringy theories have incorporated them too—a positive identification would be on par with the discovery of the Higgs particle, and would, to put it mildly, set the world of physics on fire. The scales would tilt toward string theory.

But what happens in the event—likely, according to some—that the collider yields no remotely stringy signatures?

Experimental evidence is the final arbiter of right and wrong, but a theory’s value is also assessed by the depth of influence it has on allied fields. By this measure, string theory is off the charts. Decades of analysis filling thousands of articles have had a dramatic impact on a broad swath of research cutting across physics and mathematics. Take black holes, for example. String theory has resolved a vexing puzzle by identifying the microscopic carriers of their internal disorder, a feature discovered in the 1970s by Stephen Hawking. 

Looking back, I’m gratified at how far we’ve come but disappointed that a connection to experiment continues to elude us. While my own research has migrated from highly mathematical forays into extra-dimensional arcana to more applied studies of string theory’s cosmological insights, I now hold only modest hope that the theory will confront data during my lifetime. 

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Neither string theory nor black holes have been verified by science yet.

Tremendous breakthroughs remain to be found.

It's very exciting!

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