Video Source: Quanta Magazine
Topics: Astrophysics, High Energy Physics, Particle Physics
Each week, Quanta Magazine explains one of the most important ideas driving modern research. This week, physics staff writer Charlie Wood explains why many researchers are looking to outer space for signs of “new physics.”
Fundamental physics has a problem. Some researchers say the field faces a “nightmare scenario.” Some say it’s “in crisis.” To others, it’s merely “stuck.” Whatever word they use, most particle physicists acknowledge that progress has slowed. After a rip-roaring 20th century that saw the discovery of general relativity, quantum theory, and a dozen or so fundamental particles, the first quarter of the 21st century has mainly brought further confirmation of those theories.
Physicists know their hard-won understanding of nature’s laws is incomplete. They don’t know why certain particles have mass, what sort of invisible stuff seems to be holding galaxies together, or what sort of energy is driving the universe’s expansion. But their biggest blind spot is one of scale. Physicists have equations that predict how molecules zig and zag, how atoms split, and how the heart of the atom holds together. They can continue zooming into the sub-sub-subatomic world for quite a while, but eventually — for any event playing out on a stage roughly 10⁻³⁵ meters across — they run out of equations. The universe seems to have rules that tell it what to do in those situations (it follows them during black hole formation, for instance), but physicists are ignorant of these instructions.
Particle physicists have pushed their frontier of ignorance back to this minuscule realm by repeatedly crashing particles closer and closer together, watching what happens, and developing the mathematics to capture the strange and surprising behaviors they witness. This strategy has culminated in Europe’s Large Hadron Collider, a 27-kilometer ring that can summon the energies needed to collide protons and study nature at 10⁻¹⁹ meters. The international physics community aims to build a next-generation collider — perhaps with a 100-kilometer circumference — this century. But the money, time and technology required to go much further boggles the mind. Numerous clever non-collider experiments are searching for subtle deviations from predictions and could lead to a major discovery any day, but researchers are ultimately facing similar problems as their experiments grow more and more intricate. Particle physicists are approaching a technological and financial wall as they attempt to probe ever deeper layers of reality.
One of the most promising avenues for new discoveries is the detection of ripples in space-time known as gravitational waves. Researchers have now racked up dozens of chirps originating from cataclysmic crashes between black holes, and they are rapidly developing ways of picking up cosmic clangs indicative of even more dramatic events. Particle physicists are anxiously awaiting the 2030s, when they hope to see a trio of satellites known as the Laser Interferometer Space Antenna (LISA) go into operation. If it flies, LISA will be capable of picking up gravitational waves generated during the first fractions of a second after the Big Bang, an intense era in cosmic history at the frontier of the known laws of physics. In those early moments, some physicists expect, the universe existed in multiple phases at once — like a pot of boiling water. If so, the bubbling would have set off space-time ripples that LISA will be listening for.
Why the Next Physics Revolution Might Come From Above, Charlie Wood, Quanta Magazine
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