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Where is Physics Headed (and How Soon Do We Get There)?


The longer term belongs to those that prepare for it, as scientists who petition federal agencies like NASA and the Department of Energy for research funds know all too well. The value of big-ticket instruments like an area telescope or particle accelerator might be as high as $10 billion.

And so this past June, the physics community began to think about what they wish to do next, and why.

That’s the mandate of a committee appointed by the National Academy of Sciences, called Elementary Particle Physics: Progress and Promise. Sharing the chairmanship are two distinguished scientists: Maria Spiropulu, Shang-Yi Ch’en Professor of Physics on the California Institute of Technology, and the cosmologist Michael Turner, an emeritus professor on the University of Chicago, the previous assistant director of the National Science Foundation and former president of the American Physical Society.

Within the Nineteen Eighties, Dr. Turner was among the many scientists who began using the tools of particle physics to check the Big Bang and the evolution of the universe, and the universe to find out about particle physics. Dr. Spiropulu, born in Greece, was on the team in 2012 that discovered the long-sought Higgs boson on the European Organization for Nuclear Research, often called CERN; she now uses quantum computers to research the properties of wormholes. The committee’s report is scheduled for release in June 2024.

Recently The Times met with the 2 scientists to debate the group’s progress, the disappointments of the last 20 years and the challenges ahead. The conversation has been edited for clarity and brevity.

Why convene this committee now?

Turner: I feel like things have never been more exciting in particle physics, when it comes to the opportunities to know space and time, matter and energy, and the elemental particles — in the event that they are even particles. In case you asked a particle physicist where the sector goes, you’d get a variety of different answers.

But what’s the grand vision? What’s so exciting about this field? I used to be so excited in 1980 in regards to the idea of grand unification, and that now looks small in comparison with the probabilities ahead.

You’re referring to Grand Unified Theories, or GUTs, which were considered a method to achieve Einstein’s dream of a single equation that encompassed all of the forces of nature. Where are we on unification?

Turner: So far as we all know, the fundamental constructing blocks of matter are quarks and leptons; the foundations that govern them are described by the quantum field theory called the Standard Model. Along with the constructing blocks, there are force carriers — the photon, of the electromagnetic force; eight gluons, of the strong color force; the W and Z bosons, of the weak nuclear force, and the Higgs boson, which explains why some particles have mass. The invention of the Higgs boson accomplished the Standard Model.

But the search for the elemental rules is just not over. Why two different sorts of constructing blocks? Why so many “elementary” particles? Why 4 forces? How do dark matter, dark energy, gravity and space-time slot in? Answering these questions is the work of elementary particle physics.

Spiropulu: The curveball is that we don’t understand the mass of the Higgs, which is about 125 times the mass of a hydrogen atom.

After we discovered the Higgs, the very first thing we expected was to seek out these other recent supersymmetric particles, since the mass we measured was unstable without their presence, but we haven’t found them yet. (If the Higgs field collapsed, we could bubble out into a distinct universe — and in fact that hasn’t happened yet.)

That has been somewhat bit crushing; for 20 years I’ve been chasing the supersymmetrical particles. So we’re like deer within the headlights: We didn’t find supersymmetry, we didn’t find dark matter as a particle.

Turner: The unification of the forces is just a part of what’s occurring. Nevertheless it is boring as compared to the larger questions on space and time. Discussing what space and time are and where they got here from is now throughout the realm of particle physics.

From the attitude of cosmology, the Big Bang is the origin of space and time, at the very least from the standpoint of Einstein’s general relativity. So the origin of the universe, space and time are all connected. And does the universe have an end? Is there a multiverse? What number of spaces and times are there? Does that query even make sense?

Spiropulu: To me, by the best way, unification is just not boring. Just saying.

Turner: I meant boring relatively speaking. It’s still very interesting!

Spiropulu: The strongest hint we’ve got of the unity of nature comes from particle physics. At high enough energies, the elemental forces — gravity, electromagnetism and the strong and weak nuclear forces — appear to develop into equal.

But we’ve got not reached the God scale in our particle accelerators. So possibly we’ve got to reframe the query. For my part the final word law stays a persistent puzzle, and the best way we solve it will be through recent considering.

Turner: I like what Maria is saying. It seems like we’ve got all of the pieces of the puzzle on the table; it looks just like the 4 different forces we see are only different facets of a unified force. But that might not be the proper method to phrase the query.

That’s the hallmark of great science: You ask a matter, and sometimes it seems to be the improper query, but you could have to ask a matter just to seek out out it’s the improper one. Whether it is, you ask a recent one.

String theory — the vaunted “theory of all the things” — describes the fundamental particles and forces in nature as vibrating strings of energy. Is there hope on our horizon for higher understanding it? This alleged stringiness only shows up at energies tens of millions of times higher than what might be achieved by any particle accelerator ever imagined. Some scientists criticize string theory as being outside science.

Spiropulu: It’s not testable.

Turner: Nevertheless it is a robust mathematical tool. And in case you take a look at the progress of science over the past 2,500 years, from the Milesians, who began without mathematics, to the current, mathematics has been the pacing item. Geometry, algebra, Newton and calculus, and Einstein and non-Riemannian geometry.

Spiropulu: I could be more daring and say that string theory is a framework, like other frameworks we’ve got discovered, inside which we try to elucidate the physical world. The Standard Model is a framework — and within the ranges of energies that we are able to test it, the framework has proved to be useful.

Turner: One other method to say it’s that we’ve got recent words and language to explain nature. Mathematics is the language of science, and the more our language is enriched, the more fully we are able to describe nature. We can have to attend and see what comes from string theory, but I feel it would be big.

Amongst the numerous features of string theory is that the equations appear to have 10⁵⁰⁰ solutions — describing 10⁵⁰⁰ different possible universes or much more. Will we live in a multiverse?

Turner: I feel we’ve got to take care of it, regardless that it sounds crazy. And the multiverse gives me a headache; not being testable, at the very least not yet, it isn’t science. Nevertheless it stands out as the most vital idea of our time. It’s one in all the things on the table. Headache or not, we’ve got to take care of it. It must go up or out; either it’s a part of science or it isn’t a part of science.

Why is it considered a triumph that the usual model of cosmology doesn’t say what 95 percent of the universe is? Only 5 percent of it’s atomic material like stars and folks; 25 percent is another “dark matter,” and about 70 percent is something even weirder — Mike has named it “dark energy” — that’s causing the universe to expand at an accelerating rate.

Turner: That’s an enormous success, yeah. We’ve named all the key components.

But you don’t know what most of them are.

Spiropulu: We get stalled after we reach very deep. And in some unspecified time in the future we want to alter gear — change the query or the methodology. At the tip of the day, understanding the physics of the universe is just not a walk within the park. More questions go unanswered than are answered.

If unification is the improper query, what’s the proper one?

Turner: I don’t think you may discuss space, time, matter, energy and elementary particles without talking in regards to the history of the universe.

The Big Bang looks just like the origin of space and time, and so we are able to ask, What are space and time really? Einstein showed us that they’re not only the place where things occur, as Newton said. They’re dynamical: space can bend and time can warp. But now we’re able to answer the query: Where did they arrive from?

We’re creatures of time, so we predict the universe is all about time. And that stands out as the improper method to take a look at the universe.

We have now to take note what you said earlier. Lots of the tools in particle physics take a really very long time to develop and are very expensive. These investments at all times repay, often with big surprises that change the course of science.

And that makes progress difficult. But I’m bullish on particle physics since the opportunities have never been larger and the sector has been on the bleeding fringe of science for years. Particle physics invented big, global science, and national and now global facilities. If history is any guide, nothing will prevent them from answering the large questions!

It took three a long time to construct the James Webb Space Telescope.

Spiropulu: Space — bingo!

Turner: I mean, science is all about big dreams. Sometimes the dreams are beyond your immediate reach. But science has allowed humankind to do big things — Covid vaccines, the Large Hadron Collider, the Laser Interferometer Gravitational-Wave Observatory, the Webb telescope — that stretch our vision and our power to shape our future. After we do these big things nowadays, we do them together. If we proceed to dream big and work together, much more amazing things lie ahead.

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