Wednesday, May 29

Theory of Everything: how the proper questions advance physics 2023

“What is the theory of everything?” was a common query in my undergraduate physics program 20 years ago. It labeled theoretical physicists’ efforts to explain the universe’s fundamental particles and forces.

Is it good? Does it assist scientists make breakthrough discoveries? Science requires smart questions. “Wishful thinking”?

“What is the theory of everything?” reminds us that excellent science doesn’t need good questions. I’ll clarify.

Let’s play. I have a deck of cards with animal names and photos. I pick a card, and you ask questions to determine which animal I picked. You need animal knowledge to ask a good inquiry.

You may ask “Does it live in the sea?” when you first play. No, and the game continues. Pick a card next. You examine the cards to choose and find only terrestrial creatures. “Does it live in the sea?” was a bad starting question.

We take turns, and the more we play, the faster we can guess the card. Why? Our questioning has improved.

Science uses questions similarly. We ask questions based on our understanding to enhance it. Our comprehension improves our queries and replies.

This advances. “What is the theory of everything?” is another scientific topic whose value might change.

“Theory of everything”?

The Standard Model of Particle Physics, a cornerstone of contemporary science, is a reductionist success.

Quantum field theory is used to model elementary particle movement and interaction. It describes electromagnetic, the weak and strong forces, and subatomic processes. The fourth force—gravity—is absent.

The model accounts for quantum physics, which explains subatomic particle dynamics probabilistically, and Einstein’s special theory of relativity, which specifies what occurs when relative speeds are near to the speed of light—no minor feat.

“What is the theory of everything?” assumes that the Standard Model will be embedded in a broader framework (with more elemental elements) that explains the fundamental forces, including gravity. Gravity dominates this question.

However, the inquiry “What is the theory of everything?” provides no insight into its form. Improve our questions.

The Higgs mechanism, which produces the Higgs boson, suggests that a unified explanation of the basic forces may exist. It explains why weak-force-transmitting W and Z bosons have mass. It also explains why the electromagnetic force-transmitting photon does not.

Electromagnetism, which fuels stars through nuclear fusion, works over extremely wide distances, whereas the weak force acts only over very small distances. At higher energies, these two forces become one “electroweak” force due to the Higgs process. Electroweak unification.

Why not all Standard Model forces if electromagnetism and the weak force combine? Grand unified theories propose to unify these two with the strong force, which binds atomic nuclei. Supersymmetry, which postulates a symmetry between force carriers and matter particles, suggests that these three forces might reach tantalizingly near at high energies.

Why not gravity if electromagnetic, weak, and strong forces are unified?

The General Theory of Relativity describes gravity at large sizes and low energies. Quantum field theory isn’t adequate for a consistent quantum gravity theory on the tiniest scales. We need mathematical frameworks that integrate general relativity and quantum physics.

A “theory of everything” includes all known forces of nature—electromagnetism, the weak force, the strong force, gravity, and new, hypothetical forces—and the particles they operate between. The “theory” describes everything mathematically.

What will India’s new National Quantum Mission accomplish?

String theory proposes that the universe’s fundamental building elements are microscopic strings that vibrate in additional spatial dimensions.

Better queries

Science follows questions. “What is the theory of everything?” suggests a destination but provides no direction.

Supersymmetry and string theory did not answer “What is the theory of everything?” directly. They asked better questions like: Why is there a big gap between the energy scales of the Standard Model and quantum gravity? Why is quantum mechanics incompatible with general relativity?

However, theoretical physicists’ “whys” evolve as our understanding does, and our current inquiries are bringing us closer than ever to comprehending all known forces of nature.

These new “whys” suggest surprising links between physics and mathematics: Why do holograms help us grasp gravity? Why is this related to massive random number collections? Why does quantum information explain black hole physics?

However, “out with the old and in with the new” does not apply. Instead, these new issues were derived through constructing and investigating hypothetical “Theories of Everything,” such string theory.

New inquiries are excellent. The fun part is that they may not be the greatest questions, and having them lead us doesn’t guarantee a certain outcome. Scientific discovery involves that.

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