ON A clear night, watching the stars in an inky sky, one word comes to mind: calm. The starlight seems to speak of stability and permanence. And yet, hidden from the naked eye, the wider cosmos is a place of relentless upheaval. Every 10 seconds or so, somewhere in the universe, a star reaches the end of its life and caves in on itself before exploding with cataclysmic ferocity.

For all their ubiquity, we still don’t fully understand what triggers core-collapse supernovae. But we do suspect that elusive particles called neutrinos play a key role, and that observing them in the unimaginably extreme conditions inside a supernova could betray the exotic matter and forces that would lead us to a deeper theory of particle physics. “There’s just so much information in supernova neutrinos,” says Joachim Kopp, a theorist at Johannes Gutenberg University in Mainz, Germany.

The problem is that supernovae close enough to Earth to spill their secrets are rare. The most recent one came in 1987, and the 25 neutrinos we were able to capture from the blast continue to mystify researchers to this day – which explains why so many are so excited by the new generation of neutrino detectors currently being built around the world.

The idea is that when the next nearby star goes supernova, we will be ready. But it is a race against time because that is already long overdue. “You can imagine how exciting…

Shaking a martini glass instead of the drink itself creates mesmerising patterns of small whirlpools.

Zhao Pan at the University of Waterloo, Canada, was travelling abroad when a drink he ordered in a bar led him to an intriguing physics discovery. His martini was full of bubbles, and because he was sitting by a window, he could clearly see them trace a complicated structure of vortices when he shook the glass back and forth.

Later, he repeated the process in the …

The 2023 Nobel prize in physics has been awarded to Pierre Agostini, Ferenc Krausz and Anne L’Huillier for their work on generating ultra-short pulses of light to study how electrons move through matter.

Anne L’Huillier at Lund University in Sweden, who is only the fifth woman to have won the physics Nobel, heard the news when she was midway through teaching her students. “The last half hour of my lecture was a bit difficult to do,” L’Huillier told a press conference on …

EARLY in his career, the University of Oxford mathematician Roger Penrose inspired the artist M. C. Escher to create Ascending and Descending, the visual illusion of a loop of staircase that seems to be eternally rising. It remains a fitting metaphor for Penrose’s ever enquiring mind. During his long career, he has collaborated with Stephen Hawking to uncover the secrets of the big bang, developed a quantum theory of consciousness with anaesthesiologist Stuart Hameroff and won the Nobel prize in physics for his prediction of regions where the gravitational field would be so intense that space-time itself would break down, the so-called singularity at the heart of a black hole. Undeterred by the march of time – Penrose turned 91 this year – he is continuing to innovate, and even planning communications with future universes.

Michael Brooks: In 1965, near the start of your career, you used general relativity to make the first prediction of the existence of singularities, as in the centres of black holes. How did it feel to see the first photograph of a black hole more than half a century later?

Roger Penrose: If I’m honest, it didn’t make much impression on me because I was expecting these things by then. However, back when I first proved this [singularity] theorem, it was quite a curious situation: I was visiting Princeton to give a talk and I remember Bob Dicke – a well-known cosmologist, a very distinguished man – came and slapped me on the back and said, “You’ve done it, you’ve shown general relativity is wrong!” And that was quite a common view. I suspect that even Einstein would probably have had that reaction because he was very much against the existence of singularities. I think he would have thought, “No, no, there must be something wrong with the theory”.

It seems the view had been that instead of generating a singularity, everything would swish around and come swirling out again. And I showed that this is not what happens. What I proved then doesn’t mean general relativity is wrong, but you do have to have singularities.

But despite the existence of singularities, the idea of black holes wasn’t a wild idea?

No, because at the time the quasars [extremely bright objects at the centres of galaxies] had been observed. And the strength of the signal indicated that they must be enormously large – as in massive – but also small in terms of spatial dimensions. That kind of large and small together indicated something very dense like what we now call a black hole. So it did suggest that quasars were things that were very compressed, concentrated bodies, down to the sort of level where you would see this kind of [singularity] problem arising.

Even so, at the time, black holes were not considered things you would actually get [from the mathematics]. But these arguments were looking at exact models such as the symmetrical Schwarzschild solution to the equations of general relativity, which specifically models a black hole that is not spinning and has no charge, or as in the Kerr model, a rotating, but still neutral, black hole. They don’t tell you anything about a general situation [where the presence of charge or rotation, for example, isn’t specified]. I wasn’t convinced by these arguments. The alternatives were these complicated computer calculations, which were very rudimentary at the time. They just said, “Well look: everything’s broken down!” You didn’t know whether that was because it had run out of memory or because the calculations had given up for some reason. So they didn’t tell you that singularities exist either.

Has the 2020 Nobel prize for discovering black holes mathematically made a difference to your work?

In 2020, there was a good thing and a bad thing that happened to me. I had been travelling around and didn’t have much time to think about problems. But because of the [pandemic] lockdown, I was able to work out certain ideas that have been buzzing around in my head. I wrote down some notes and sent them around to colleagues, and this then ended up being a paper – which may well end up being a book that I hope to do at some stage. This was the good thing.

The bad thing was getting the Nobel prize because it stopped the whole thing dead. I’m being a bit unfair really, but I haven’t done anything on these notes since getting the Nobel prize; there’s just been no time. I should add that it’s a bit misleading to say I got the Nobel prize for black holes. The citation said that I showed black holes are a robust prediction of Einstein’s general theory of relativity. What I really showed is that singularities are a robust prediction of general relativity.

Could a singularity exist without giving rise to a black hole?

We believe you only get singularities that are hidden behind event horizons [boundaries beyond which nothing, not even light, can escape from the gravitational pull] – that is, a black hole. But maybe you could get “naked” singularities without an event horizon around them, and information could come out of them.

As far as I’m aware, there is still no proof that, in the general case, you do not get naked singularities: it’s still a conjecture. Nobody seems to talk seriously about it much – the general community is sort of resigned to the idea that what you get is black holes. But then lots of questions arise, and I feel that most of these questions are going along the wrong track.

What new cosmological ideas are you working on now?

I’m just writing a paper with a colleague about “conformal cyclic cosmology” (CCC). This is the view that the big bang was not actually the origin of our universe, but the continuation of the remote future of a previous aeon. So the universe expands and contracts and then indulges in this exponential expansion which we now see in our own aeon, where the expansion of the universe accelerates. And it continues.

So with CCC you’re arguing that the universe cyclically balloons and compresses and what we refer to as the big bang is merely the beginning of this aeon, the period of the universe’s life that we are living through, rather than the actual start of everything. Would it be fair to say that this idea hasn’t had a lot of pick up from the rest of the physics community?

You’re absolutely right: it does not get a lot of pick up. I find that when I give talks to people who are not physicists, they latch on to it much more easily than the people who are conventional cosmologists, very few of whom take me seriously. But I don’t fully understand why because CCC does have observational implications and the evidence for it is really quite strong. What we claimed to see in this paper is something we called a “Hawking Point” – a point ringed with polarised light, left by a black hole from a previous aeon. I hate to say this, but this reluctance to consider a new idea in the face of strong evidence is one reason why I think people should worry about science.

Another of your controversial ideas is the one put forward in your 1989 book The Emperor’s New Mind: that consciousness involves quantum effects. I know it has evolved into the idea of “orchestrated objective reduction” (Orch OR), but is it something that you still stand by?

When I wrote that book, I had thought that I would see how quantum mechanics comes into the manifestation of consciousness by the time I got to the end of it. But I sort of gave up on that hope in the end – I had to finish the book somehow, so I did something I didn’t really believe in and I shut up about that particular idea.

However, I thought the exploration of how computing and physics relate to the mind might at least stimulate young people to do physics. Yet pretty much all the letters I got were from old, retired people. However, there was one from [US anaesthesiologist] Stuart Hameroff. He had the view that consciousness had to do not with nerve transmission, as everybody else seemed to think, but with microtubules, these little tiny structures much, much smaller than nerves. It seemed much more promising. So we got together and did things – though we didn’t quite know what we were doing. There are certain rough edges to our Orch OR argument, but whatever consciousness is, it must be beyond computable physics.

If you think consciousness is beyond computation, does that mean you think it is beyond what science can discern?

No, it’s just beyond current science. My claim is much worse, much more serious, much more outrageous than “it’s quantum mechanics in the brain”. It’s not that consciousness depends on quantum mechanics, it’s that it depends on where our current theories of quantum mechanics go wrong. It’s to do with a theory that we don’t know yet.

But I think we have made some progress. There are about four mainstream views about what consciousness is, and one of them is this Orch OR idea that Hameroff and I developed. That’s a bit of a shift. People used to say it is completely crazy, but I think people take it seriously now. There are also experiments looking at phenomena to do with quantum effects and to do with effects of general anaesthetics, and there do seem to be some connections there. So it’s coming into the area of experimental confirmation or refutation; I find that exciting.

Can you remember what it was that first excited you about maths and physics?

I got a lot from my father: we used to do things like making polyhedra and variations of “platonic solids” [polyhedra with sides of equal lengths] and other things in mathematics. Also, I learned quite a bit from my older brother Oliver. He was very precocious – unlike me. I was very slow at school. This was still the case when I did mathematics at University College London.

I remember that I chose two geometric projects for my special topics and those were not my best papers. I could see how to do the problem using the geometrical part of the brain, if you like, but I had to translate that into words and that was slow, so I didn’t finish the papers. I tend to think visually, and I think there’s a big selection effect: people who think visually tend not to do so well as the people who think the other way. You probably lose quite a lot of people who would be good mathematicians because they’re largely visual.

What is your advice for people starting their career in physics now – what to get involved in or what to avoid?

That’s a difficult one: it would be very easy for me to impose my prejudices. There’s a lot of work in particle physics, for instance, and clearly a lot of progress is made in that subject. But I find it very hard. A lot of what you have to do in particle physics depends on doing things which aren’t logical: if something crops up as infinite, you can ignore it. It’s probably a kind of instinct that some people have; I don’t think I have that kind of instinct. I want to be logical. If it doesn’t hang together, I can’t see my way through it.

You have spent decades thinking about the structure of the universe, and about consciousness. Does this give you any sense of whether there is inherent meaning in the universe?

In a certain sense you might say that the universe has a purpose, but I’m not sure what the purpose is. I don’t believe in any religion I’ve seen. So in that sense, I am an atheist. However, I would say that there is something going on that might resonate with a religious perspective.

I think the presence of consciousness, if I can put it like that, is not an accident. It’s a bit complicated to say what I really mean by this, but it has a connection with the fact that nobody knows where the fundamental constants of nature come from. If they didn’t have the particular values that they have, then maybe we wouldn’t have interesting chemistry, and then wouldn’t have life. I find that a difficult argument to make clear, because you don’t know – if the numbers were different – what kind of thing you might call life. However, it raises a question to do with conformal cyclic cosmology: do the constants get jumbled up each time you go round to the next aeon?

Do you mean that according to CCC, consciousness and the fundamentals of physics would look different from one aeon to the next?

It’s an interesting question, and it relates to something I wrote with a colleague where we look into conformal cyclic cosmology for a signal coming from the previous aeon, which would suggest some consistency in the underlying physics between one aeon and the next. It’s due to the collision between supermassive black holes: they produce gravitational wave signals, which we should be able to see the implications of in our aeon. And the claim is that we do. Again, people dispute this, but I think they are pretty strong arguments: there’s something going on there.

So these signals that traverse the aeons might support some underlying purpose in the universe?

Well, our argument starts from the fact that I’m not all that optimistic we’re going to go on for a huge length of time. The probability that something will trigger a nuclear catastrophe is not that tiny – in fact, I think we’re pretty lucky to be around now. But maybe other civilisations will be more sensible and settle down. In fact, I think some version of SETI [the search for extraterrestrial intelligence] should look for different civilisations, successful ones that survived very late in the previous aeon. That may be more promising in some respects. But maybe we, maybe others, will learn how to send signals into the next aeon. Probably gravitational wave signals are the best bet, but very, very low variations in the electromagnetic field could get through too. And we might be able to get them to do better than we have, by saying, “No, you stupid idiots, that’s what we’re doing!”

Topics:

• quantum mechanics/
• consciousness

The standard model of particle physics is often illustrated as a simple grid showing the 17 basic particles (shown above). But an alternative way of visualising it reveals the complex rules that govern how the particles and forces interact.

The conventional grid shows three generations of quarks (which feel the strong force) and leptons (which don’t). Then there are the bosons that mediate three of the fundamental forces of nature – the strong and weak nuclear forces and electromagnetism. But it doesn’t give us the full picture.

For one, there are parts missing, like the fact that most particles can occur in two forms of a property called handedness: right-handed and left-handed. It also tells us nothing about which particles feel which forces. There are mysteries it glosses over, too, like the fact there are no right-handed neutrinos, at least that we know of. “The standard grid, as lovely as it is, looks finished,” says Chris Quigg, a theoretical physicist at the Fermi National Accelerator Laboratory in Illinois. “But the standard model is not finished.”

Quigg thought we needed a new way to visualise the theory that reflected its messiness. In 2005, he came up with his answer: the double simplex (shown above). Made of two pyramids, linked by the Higgs boson, one half represents left-handed particles and the other right-handed ones. Each pyramid vertex groups generations of …

IN 1973, physicist Steven Weinberg gave a talk in Aix-en-Provence, France. It was there, according to Weinberg, that he first used the term “standard model” to describe the nascent description of the fundamental constituents of the universe and their interactions. Fifty years on, the standard model of particle physics is a stunningly accurate picture of what everything is made of and how it all works to produce reality.

Practically everything, anyway. Because although the 50th anniversary is well worth celebrating, it is impossible to ignore the fact that the theory is incomplete. It doesn’t explain gravity, or why we have so much matter in the universe and so little antimatter. And it says nothing about so-called dark matter and dark energy, postulated to explain why the cosmos behaves in certain ways.

This is why physicists are casting around for clues that could lead us to a better theory. But which, if any, will deliver an upgrade to the standard model? How do we find the deluxe version? We let six of today’s leading physicists explain how they think we will finally discover a more complete picture of reality.

Collisions at the energy frontier

Jon Butterworth

University College London

It is always risky to bet against the standard model of particle physics. Historically, most people who have done so have lost. But over the next decade and a half, the Large Hadron Collider (LHC) will continue …

The heaviest version of oxygen ever created falls apart mysteriously quickly. This finding implies a problem with our understanding of a fundamental forces of nature.

Yosuke Kondo at the Tokyo Institute of Technology in Japan and his colleagues created oxygen-28 – an isotope of oxygen with eight protons and 20 neutrons – by smashing an energetic beam of fluorine atoms into liquid hydrogen.

The fluorine atoms each had 20 neutrons and nine protons. When they collided with the liquid hydrogen, they each lost a proton, turning the atoms into oxygen-28. The researchers expected these atoms to be stable. But instead, they found that they only existed for about a zeptosecond, or trillionth of a billionth of a second, and then decayed into the less heavy oxygen-24 and four neutrons.

“This is extremely surprising. It opens a very, very big fundamental question about nature’s strongest interaction, the nuclear strong force,” says Rituparna Kanungo at Saint Mary’s University in Canada, who was not involved with the experiment. The strong force binds quarks together to make protons and neutrons, but our understanding of how exactly it works when all those particles show up in large numbers is currently incomplete, she says.

Kondo and his team expected that oxygen-28 would hang around a lot longer because it was thought to be “doubly magic”.

Within the nucleus of every atom, protons and neutrons are grouped into shells, each of which can accommodate specific numbers of particles. When all occupied shells are fully filled, the number of particles within them is called “magic” and the nucleus that they comprise becomes extremely stable.

If both protons and neutrons fully fill an atom’s shells, then it is called doubly magic. The oxygen that sustains life on Earth has this property, which is what allows it to be so abundant.

Through various studies of isotopes like calcium-40 and nickel-48, seven numbers are widely recognised as being magic, including the number 20 for neutrons. The new experiment challenges this idea.

Theoretical models will have to be re-made, and more experiments will need to be done in order to get a sense of what the particles inside oxygen-28 actually do if they are not in full and stable shells, says Kanungo.

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