It's all quantum ... maybe

In a dramatic twist on classical physics, scientists have cooled a mirror to near absolute zero with lasers to see if gravity might be quantum. This breakthrough could reshape how we understand the universe.
  Credit: SciTechDaily.com

It's all quantum, maybe. The Standard Model covers all things related to forces and matter save for gravity, the most mysterious entity of all as researchers are trying to find out, is gravity quantum like that of electromagnetic, the strong force and the weak? If so, the possibility of finally uniting quantum to relativity may be nigh.

The elementary particles of the Standard Model are:[7]

Six "flavors" of quarks: up, down, strange, charm, bottom, and top;

Six types of leptons: electron, electron neutrino, muon, muon neutrino, tau, tau neutrino;

Twelve gauge bosons (force carriers): the photon of electromagnetism, the three W and Z bosons of the weak force, and the eight gluons of the strong force;

The Higgs boson.

 

Overlap between bosons, hadrons, and fermions

The Standard Model's Particle zoo.

The Gravity Puzzle: Is It Quantum?

One of the most profound open questions in modern physics is: “Is gravity quantum?”

While the other fundamental forces—electromagnetic, weak nuclear, and strong nuclear—have been successfully described by quantum theory, gravity still stands apart. So far, scientists haven’t been able to create a consistent quantum theory of gravity, leaving a major gap in our understanding of the universe.

“Theoretical physicists have proposed many possible scenarios, from gravity being inherently classical to fully quantum, but the debate remains unresolved because we’ve never had a clear way to test gravity’s quantum nature in the lab,” says Dongchel Shin, a PhD candidate in the MIT Department of Mechanical Engineering (MechE). “The key to answering this lies in preparing mechanical systems that are massive enough to feel gravity, yet quiet enough — quantum enough — to reveal how gravity interacts with them.”

A piece of the optical setup from the MIT Quantum and Precision Measurements Group lab.
Credit: Tony Pulsone/MechE

The quest ...

Merging Atomic Physics and Gravitational Tools

By using lasers to remove nearly all thermal motion from atoms, in recent decades scientists have created ultracold atomic gases at micro- and nanokelvin temperatures. These systems now power the world’s most precise clocks — optical lattice clocks — with timekeeping precision so high that they would gain or lose less than a second over the age of the universe.

“Historically, these two technologies developed separately — one in gravitational physics, the other in atomic and optical physics,” says Shin. “In our work, we bring them together. By applying laser cooling techniques originally developed for atoms to a centimeter-scale torsional oscillator, we try to bridge the classical and quantum worlds. This hybrid platform enables a new class of experiments — ones that could finally let us test whether gravity needs to be described by quantum theory.”

Read on brave reader to see how the TOE might finally come to pass. :)