The universe’s maximum lifespan may be considerably shorter than was previously thought, but don’t worry: there’s still plenty of time to finish streaming your favourite TV series.
According to new calculations by black hole expert Heino Falcke, quantum physicist Michael Wondrak, and mathematician Walter van Suijlekom of Radboud University in the Netherlands, the most persistent stellar objects in the universe – white dwarf stars – will decay away to nothingness in around 1078 years. This, Falcke admits, is “a very long time”, but it’s a far cry from previous predictions, which suggested that white dwarfs could persist for at least 101100 years. “The ultimate end of the universe comes much sooner than expected,” he says.
Writing in the Journal of Cosmology and Astroparticle Physics, Falcke and colleagues explain that the discrepancy stems from different assumptions about how white dwarfs decay. Previous calculations of their lifetime assumed that, in the absence of proton decay (which has never been observed experimentally), their main decay process would be something called pyconuclear fusion. This form of fusion occurs when nuclei in a crystalline lattice essentially vibrate their way into becoming fused with their nearest neighbours.
If that sounds a little unlikely, that’s because it is. However, in the dense, cold cores of white dwarf stars, and over stupendously long time periods, pyconuclear fusion happens often enough to gradually (very, very gradually) turn the white dwarf’s carbon into nickel, which then transmutes into iron by emitting a positron. The resulting iron-cored stars are known as black dwarfs, and some theories predict that they will eventually (very, very eventually) collapse into black holes. Depending on how massive they were to start with, the whole process takes between 101100‒1032 000 years.
An alternative mechanism
Those estimates, however, do not take into account an alternative decay mechanism known as Hawking radiation. First proposed in the early 1970s by Stephen Hawking and Jacob Bekenstein, Hawking radiation arises from fluctuations in the vacuum of spacetime. These fluctuations allow particle-antiparticle pairs to pop into existence by essentially “borrowing” energy from the vacuum for brief periods before the pairs recombine and annihilate.
If this pair production happens in the vicinity of a black hole, one particle in the pair may stray over the black hole’s event horizon before it can recombine. This leaves its partner free to carry away some of the “borrowed” energy as Hawking radiation. After an exceptionally long time – but, crucially, not as long as the time required to disappear a white dwarf via pyconuclear fusion – Hawking radiation will therefore cause black holes to dissipate.
The fate of life, the universe and everything?
But what about objects other than black holes? Well, in a previous work published in 2023, Falcke, Wondrak and van Suijlekom showed that a similar process can occur for any object that curves spacetime with its gravitational field, not just objects that have an event horizon. This means that white dwarfs, neutron stars, the Moon and even human beings can, in principle, evaporate away into nothingness via Hawking radiation – assuming that what the trio delicately call “other astrophysical evolution and decay channels” don’t get there first.
Based on this tongue-in-cheek assumption, the trio calculated that white dwarfs will dissipate in around 1078 years, while denser objects such as black holes and neutron stars will vanish in no more than 1067 years. Less dense objects such as humans, meanwhile, could persist for as long as 1090 years – albeit only in a vast, near-featureless spacetime devoid of anything that would make life worth living, or indeed possible.
While that might sound unrealistic as well as morbid, the trio’s calculations do have a somewhat practical goal. “By asking these kinds of questions and looking at extreme cases, we want to better understand the theory,” van Suijlekom says. “Perhaps one day, we [will] unravel the mystery of Hawking radiation.”
The Mars rover Perseverance has captured the first image of an aurora as seen from the surface of another planet. The visible-light image, which was taken during a solar storm on 18 March 2024, is not as detailed or as colourful as the high-resolution photos of green swirls, blue shadows and pink whorls familiar to aurora aficionados on Earth. Nevertheless, it shows the Martian sky with a distinctly greenish tinge, and the scientists who obtained it say that similar aurorae would likely be visible to future human explorers.
“Kind of like with aurora here on Earth, we need a good solar storm to induce a bright green colour, otherwise our eyes mostly pick up on a faint grey-ish light,” explains Elise Wright Knutsen, a postdoctoral researcher in the Centre for Space Sensors and Systems at the University of Oslo, Norway. The storm Knutsen and her colleagues captured was, she adds, “rather moderate”, and the aurora it produced was probably too faint to see with the naked eye. “But with a camera, or if the event had been more intense, the aurora will appear as a soft green glow covering more or less the whole sky.”
The role of planetary magnetic fields
Aurorae happen when charged particles from the Sun – the solar wind – interact with the magnetic field around a planet. On Earth, this magnetic field is the product of an internal, planetary-scale magnetic dynamo. Mars, however, lost its dynamo (and, with it, its oceans and its thick protective atmosphere) around four billion years ago, so its magnetic field is much weaker. Nevertheless, it retains some residual magnetization in its southern highlands, and its conductive ionosphere affects the shape of the nearby interplanetary magnetic field. Together, these two phenomena give Mars a hybrid magnetosphere too feeble to protect its surface from cosmic rays, but strong enough to generate an aurora.
Scientists had previously identified various types of aurorae on Mars (and every other planet with an atmosphere in our solar system) in data from orbiting spacecraft. However, no Mars rover had ever observed an aurora before, and all the orbital aurora observations, from Mars and elsewhere, were at ultraviolet wavelengths.
Awesome sight: An artist’s impression of the aurora and the Perseverance rover. (Courtesy: Alex McDougall-Page)
How to spot an aurora on Mars
According to Knutsen, the lack of visible-light, surface-based aurora observations has several causes. First, the visible-wavelength instruments on Mars rovers are generally designed to observe the planet’s bright “dayside”, not to detect faint emissions on its nightside. Second, rover missions focus primarily on geology, not astronomy. Finally, aurorae are fleeting, and there is too much demand for Perseverance’s instruments to leave them pointing at the sky just in case something interesting happens up there.
“We’ve spent a significant amount of time and effort improving our aurora forecasting abilities,” Knutsen says.
Getting the timing of observations right was the most challenging part, she adds. The clock started whenever solar satellites detected events called coronal mass ejections (CMEs) that create unusually strong pulses of solar wind. Next, researchers at the NASA Community Coordinated Modeling Center simulated how these pulses would propagate through the solar system. Once they posted the simulation results online, Knutsen and her colleagues – an international consortium of scientists in Belgium, France, Germany, the Netherlands, Spain, the UK and the US as well as Norway – had a decision to make. Was this CME likely to trigger an aurora bright enough for Perseverance to detect?
If the answer was “yes”, their next step was to request observation time on Perseverance’s SuperCam and Mastcam-Z instruments. Then they had to wait, knowing that although CMEs typically take three days to reach Mars, the simulations are only accurate to within a few hours and the forecast could change at any moment. Even if they got the timing right, the CME might be too weak to trigger an aurora.
“We have to pick the exact time to observe, the whole observation only lasts a few minutes, and we only get one chance to get it right per solar storm,” Knutsen says. “It took three unsuccessful attempts before we got everything right, but when we did, it appeared exactly as we had imagined it: as a diffuse green haze, uniform in all directions.”
Future observations
Writing in Science Advances, Knutsen and colleagues say it should now be possible to investigate how Martian aurorae vary in time and space – information which, they note, is “not easily obtained from orbit with current instrumentation”. They also point out that the visible-light instruments they used tend to be simpler and cheaper than UV ones.
“This discovery will open up new avenues for studying processes of particle transport and magnetosphere dynamics,” Knutsen tells Physics World. “So far we have only reported our very first detection of this green emission, but observations of aurora can tell us a lot about how the Sun’s particles are interacting with Mars’s magnetosphere and upper atmosphere.”
Vaire Computing is a start-up seeking to commercialize computer chips based on the principles of reversible computing – a topic Earley studied during her PhD in applied mathematics and theoretical physics at the University of Cambridge, UK. The central idea behind reversible computing is that reversible operations use much less energy, and thus generate much less waste heat, than those in conventional computers.
What skills do you use every day in your job?
In an early-stage start-up environment, you have to wear lots of different hats. Right now, I’m planning for the next few years, but I’m also very deep into the engineering side of Vaire, which spans a lot of different areas.
The skill I use most is my ability to jump into a new field and get up to speed with it as quickly as possible, because I cannot claim to be an expert in all the different areas we work in. I cannot be an expert in integrated circuit design as well as developing electronic design automation tooling as well as building better resonators. But what I can do is try to learn about all these things at as deep a level as I can, very quickly, and then guide the people around me with higher-level decisions while also having a bit of fun and actually doing some engineering work.
What do you like best and least about your job?
We have so many great people at Vaire, and being able to talk with them and discuss all the most interesting aspects of their specialities is probably the part I like best. But I’m also enjoying the fact that in a few years, all this work will culminate in an actual product based on things I worked on when I was in academia. I love theory, and I love thinking about what could be possible in hundreds of years’ time, but seeing an idea get closer and closer to reality is great.
The part I have more of a love-hate relationship with is just how intense this job is. I’m probably intrinsically a workaholic. I don’t think I’ve ever had a good balance in terms of how much time I spend on work, whether now or when I was doing my PhD or even before. But when you are responsible for making your company succeed, that degree of intensity becomes unavoidable. It feels difficult to take breaks or to feel comfortable taking breaks, but I hope that as our company grows and gets more structured, that part will improve.
What do you know now that you wish you’d known when you were starting out in your career?
There are so many specifics of what it means to build a computer chip that I wish I’d known. I may even have suffered a little bit from the Dunning–Kruger effect [in which people with limited experience of a particular topic overestimate their knowledge] at the beginning, thinking, “I know what a transistor is like. How hard can it be to build a large-scale integrated circuit?”
It turns out it’s very, very hard, and there’s a lot of complexity around it. When I was a PhD student, it felt like there wasn’t that big a gap between theory and implementation. But there is, and while to some extent it’s not possible to know about something until you’ve done it, I wish I’d known a lot more about chip design a few years ago.
Imagine, if you will, that you are a quantum system. Specifically, you are an unstable quantum system – one that would, if left to its own devices, rapidly decay from one state (let’s call it “awake”) into another (“asleep”). But whenever you start to drift into the “asleep” state, something gets in the way. Maybe it’s a message pinging on your phone. Maybe it’s a curious child peppering you with questions. Whatever it is, it jolts you out of your awake–asleep superposition and projects you back into wakefulness. And because it keeps happening faster than you can fall asleep, you remain awake, diverted from slumber by a stream of interruptions – or, in quantum terms, measurements.
This phenomenon of repeated measurements “freezing” an unstable quantum system into a particular state is known as the quantum Zeno effect (figure 1). Named after a paradox from ancient Greek philosophy, it was hinted at in the 1950s by the scientific polymaths Alan Turing and John von Neumann but only fully articulated in 1977 by the physicists Baidyanath Misra and George Sudarshan (J. Math. Phys.18 756). Since then, researchers have observed it in dozens of quantum systems, including trapped ions, superconducting flux qubits and atoms in optical cavities. But the apparent ubiquitousness of the quantum Zeno effect cannot hide the strangeness at its heart. How does the simple act of measuring a quantum system have such a profound effect on its behaviour?
A watched quantum pot
“When you come across it for the first time, you think it’s actually quite amazing because it really shows that the measurement in quantum mechanics influences the system,” says Daniel Burgarth, a physicist at the Friedrich-Alexander-Universität in Erlangen-Nürnberg, Germany, who has done theoretical work on the quantum Zeno effect.
Giovanni Barontini, an experimentalist at the University of Birmingham, UK, who has studied the quantum Zeno effect in cold atoms, agrees. “It doesn’t have a classical analogue,” he says. “I can watch a classical system doing something forever and it will continue doing it. But a quantum system really cares if it’s watched.”
1 A watched quantum pot
(Illustration courtesy: Mayank Shreshtha; Zeno image public domain; Zeno crop CC BY S Perquin)
Applying heat to a normal, classical pot of water will cause it to evolve from state 1 (not boiling) to state 2 (boiling) at the same rate regardless of whether anyone is watching it (even if it doesn’t seem like it). In the quantum world, however, a system that would normally evolve from one state to the other if left unobserved (blindfolded Zeno) can be “frozen” in place by repeated frequent measurements (eyes-open Zeno).
For the physicists who laid the foundations of quantum mechanics a century ago, any connection between measurement and outcome was a stumbling block. Several tried to find ways around it, for example by formalizing a role for observers in quantum wavefunction collapse (Niels Bohr and Werner Heisenberg); introducing new “hidden” variables (Louis de Broglie and David Bohm); and even hypothesizing the creation of new universes with each measurement (the “many worlds” theory of Hugh Everett).
But none of these solutions proved fully satisfactory. Indeed, the measurement problem seemed so intractable that most physicists in the next generation avoided it, preferring the approach sometimes described – not always pejoratively – as “shut up and calculate”.
Today’s quantum physicists are different. Rather than treating what Barontini calls “the apotheosis of the measurement effect” as a barrier to overcome or a triviality to ignore, they are doing something few of their forebears could have imagined. They are turning the quantum Zeno effect into something useful.
Noise management
To understand how freezing a quantum system by measuring it could be useful, consider a qubit in a quantum computer. Many quantum algorithms begin by initializing qubits into a desired state and keeping them there until they’re required to perform computations. The problem is that quantum systems seldom stay where they’re put. In fact, they’re famously prone to losing their quantum nature (decohering) at the slightest disturbance (noise) from their environment. “Whenever we build quantum computers, we have to embed them in the real world, unfortunately, and that real world causes nothing but trouble,” Burgarth says.
Quantum scientists have many strategies for dealing with environmental noise. Some of these strategies are passive, such as cooling superconducting qubits with dilution refrigerators and using electric and magnetic fields to suspend ionic and atomic qubits in a vacuum. Others, though, are active. They involve, in effect, tricking qubits into staying in the states they’re meant to be in, and out of the states they’re not.
The quantum Zeno effect is one such trick. “The way it works is that we apply a sequence of kicks to the system, and we are actually rotating the qubit with each kick,” Burgarth explains. “You’re rotating the system, and then effectively the environment wants to rotate it in the other direction.” Over time, he adds, these opposing rotations average out, protecting the system from noise by freezing it in place.
Quantum state engineering
While noise mitigation is useful, it’s not the quantum Zeno application that interests Burgarth and Barontini the most. The real prize, they agree, is something called quantum state engineering, which is much more complex than simply preventing a quantum system from decaying or rotating.
The source of this added complexity is that real quantum systems – much like real people – usually have more than two states available to them. For example, the set of permissible “awake” states for a person – the Hilbert space of wakefulness, let’s call it – might include states such as cooking dinner, washing dishes and cleaning the bathroom. The goal of quantum state engineering is to restrict this state-space so the system can only occupy the state(s) required for a particular application.
As for how the quantum Zeno effect does this, Barontini explains it by referring to Zeno’s original, classical paradox. In the fifth century BCE, the philosopher Zeno of Elea posed a conundrum based on an arrow flying through the air. If you look at this arrow at any possible moment during its flight, you will find that in that instant, it is motionless. Yet somehow, the arrow still moves. How?
In the quantum version, Barontini explains, looking at the arrow freezes it in place. But that isn’t the only thing that happens. “The funniest thing is that if I look somewhere, then the arrow cannot go where I’m looking,” he says. “It will have to go around it. It will have to modify its trajectory to go outside my field of view.”
By shaping this field of view, Barontini continues, physicists can shape the system’s behaviour. As an example, he cites work by Serge Haroche, who shared the 2012 Nobel Prize for Physics with another notable quantum Zeno experimentalist, David Wineland.
In 2014 Haroche and colleagues at the École Normale Supérieure (ENS) in Paris, France, sought to control the dynamics of an electron within a so-called Rydberg atom. In this type of atom, the outermost electron is very weakly bound to the nucleus and can occupy any of several highly excited states.
The researchers used a microwave field to divide 51 of these highly excited Rydberg states into two groups, before applying radio-frequency pulses to the system. Normally, these pulses would cause the electron to hop between states. However, the continual “measurement” supplied by the microwave field meant that although the electron could move within either group of states, it could not jump from one group to the other. It was stuck – or, more precisely, it was in a special type of quantum superposition known as a Schrödinger cat state.
Restricting the behaviour of an electron might not sound very exciting in itself. But in this and other experiments, Haroche and colleagues showed that imposing such restrictions brings forth a slew of unusual quantum states. It’s as if telling the system what it can’t do forces it to do a bunch of other things instead, like a procrastinator who cooks dinner and washes dishes to avoid cleaning the bathroom. “It really enriches your quantum toolbox,” explains Barontini. “You can generate an entangled state that is more entangled or methodologically more useful than other states you could generate with traditional means.”
Just what is a measurement, anyway?
As well as generating interesting quantum states, the quantum Zeno effect is also shedding new light on the nature of quantum measurements. The question of what constitutes a “measurement” for quantum Zeno purposes turns out to be surprisingly broad. This was elegantly demonstrated in 2014, when physicists led by Augusto Smerzi at the Università di Firenze, Italy, showed that simply shining a resonant laser at their quantum system (figure 2) produced the same quantum Zeno dynamics as more elaborate “projective” measurements – which in this case involved applying pairs of laser pulses to the system at frequencies tailored to specific atomic transitions. “It’s fair to say that almost anything causes a Zeno effect,” says Burgarth. “It’s a very universal and easy-to-trigger phenomenon.”
2 Experimental realization of quantum Zeno dynamics
(First published in Nature Commun.5 3194. Reproduced with permission from Springer Nature)
The energy level structure of a population of ultracold 87Rb atoms, evolving in a five-level Hilbert space given by the five spin orientations of the F=2 hyperfine ground state. An applied RF field (red arrows) couples neighbouring quantum states together and allows atoms to “hop” between states. Normally, atoms initially placed in the |F, mF> = |2,2> state would cycle between this state and the other four F=2 states in a process known as Rabi oscillation. However, by introducing a “measurement” – shown here as a laser beam (green arrow) resonant with the transition between the |1,0> state and the |2,0> state – Smerzi and colleagues drastically changed the system’s dynamics, forcing the atoms to oscillate between just the |2,2> and |2,1> states (represented by up and down arrows on the so-called Bloch sphere at right). An additional laser beam (orange arrow) and the detector D were used to monitor the system’s evolution over time.
Other research has broadened our understanding of what measurement can do. While the quantum Zeno effect uses repeated measurements to freeze a quantum system in place (or at least slow its evolution from one state to another), it is also possible to do the opposite and use measurements to accelerate quantum transitions. This phenomenon is known as the quantum anti-Zeno effect, and it has applications of its own. It could, for example, speed up reactions in quantum chemistry.
Over the past 25 years or so, much work has gone into understanding where the ordinary quantum Zeno effect leaves off and the quantum anti-Zeno effect begins. Some systems can display both Zeno and anti-Zeno dynamics, depending on the frequency of the measurements and various environmental conditions. Others seem to favour one over the other.
But regardless of which version turns out to be the most important, quantum Zeno research is anything but frozen in place. Some 2500 years after Zeno posed his paradox, his intellectual descendants are still puzzling over it.
In 2014 the American mathematical physicist S James Gates Jr shared his “theorist’s bucket list” of physics discoveries he would like to see happen before, as he puts it, he “shuffles off this mortal coil”. A decade later, Physics World’s Margaret Harris caught up once more with Gates, who is now at the University of Maryland, US, to see what discoveries he can check off his list; what he would still like to see discovered, proven or explored; and what more he might add to the list, as of 2025.
The first thing on your list 10 years ago was the discovery of the Higgs boson, which had happened. The next thing on your list was gravitational waves.
The initial successful detection of gravity waves [in 2015] was a spectacular day for a lot of us. I had been following the development of that detector [the Laser Interferometer Gravitational-wave Observatory, or LIGO] almost from its birth. The first time I heard about detecting gravity waves was around 1985. I was a new associate professor at Maryland, and a gentleman by the name of [Richard] Rick Isaacson, who was a programme officer at the National Science Foundation (NSF), called me one day into his office to show me a proposal from a Caltech-MIT collaboration to fund a detector. I read it and I said this will never work. Fortunately, Isaacson is a superhero and made this happen because for decades he was the person in the NSF with the faith that this could happen; so when it did, it was just an amazing day.
Why is the discovery of these gravitational waves so exciting for physicists?
Albert Einstein’s final big prediction was that there would be observable gravitational waves in the universe. It’s very funny – if you go back into the literature, he first says yes this is possible, but at some point he changes his mind again. It’s very interesting to think about how human it is to bounce back and forth, and then to have Mother Nature say look, you got it right the first time. So such a sharp confirmation of the theory of general relativity was unlike anything I could imagine happening in my lifetime, quite frankly, even though it was on my bucket list.
The other thing is that our species knows about the heavens mostly because there have been “entities” that are similar to Mercury, the Greek god who carried messages from Mount Olympus. In our version of the story, Mercury is replaced by photons. It’s light that has been telling us for hundreds of thousands of years, maybe a million years, that there’s something out there and this drove the development of science for several hundred years. With the detection of gravitational waves, there’s a new kid on the block to deliver the message, and that’s the graviton. Just like light, it has both particle and wave aspects, so now we have detected gravitational waves, the next big thing is to be able to detect gravitons.
We are not completely clear on exactly how to see gravitons, but once we have that knowledge, we will be able to do something that we’ve never been able to do as a species in this universe. After the initial moments of the Big Bang, there was a period of darkness, when matter was far too hot to form neutral atoms, and light could not travel through the dense plasma. It took 380,000 years for electrons to be trapped in orbits around nuclei, forming the first atoms.
Eventually, the universe had expanded so much that the average temperature and density of particles had dropped enough for light to travel. Now what’s really interesting is if you look at the universe via photons, you can only look so far back up to that point when light was first able to travel through the universe, often referred to as the “first dawn”. We detected this light in the 1960s, and it’s called the cosmic microwave background. If you want to peer further back in time beyond this period, you can’t use light but you can use gravitational waves. We will be able as a species eventually to look maybe all the way back to the Big Bang, and that’s remarkable.
What’s the path to seeing gravitons experimentally?
At the time that gravitational waves were detected by LIGO there were three different detectors, two in the US and one on the border of France and Italy called Virgo. There is a new LIGO site coming online in India now, and so what’s going to happen, provided there continues to be a global consensus on continuing to do this science, is that more sites like this are going to come online, which will give us higher-fidelity pictures. It’s going to be a difference akin to going from black and white TV to colour.
Wish fulfilled Aerial view of the Virgo detector in Italy. This facility became the third to detect gravitational waves, in 2017, after the two LIGO detectors in the US. As more gravitational-wave facilities come online around the world, we increase our chance of detecting gravitons. (CCO 1.0 The Virgo collaboration)
In the universe now, the pathway to detecting gravitons involves two steps. First, you probably want to measure the polarization of gravitons, and Fabry–Pérot interferometers, such as LIGO, have that capacity. If it’s a polarized graviton wave, the bending of space-time has a certain signature, whether it’s left or right-handed. If we are lucky enough we will actually see that polarization, I would guess within the next 10 years.
The second step is quantization, which is going to be a challenge. Back in the 1960s a physicist at the University of Maryland named Joseph Weber developed what are now called Weber bars. They’re big metal bars and the idea was you cool them down and then if a graviton impinges on these bars, it would induce lattice vibrations in the metal, and you would detect those. I suspect there’s going to be a big push in going back and upgrading that technology. One of the most exciting things about that is they might be quantum Weber bars. That’s the road that I could see to actually nailing down the existence of the graviton.
Number three on your bucket list from a decade ago was supersymmetry. How have its prospects developed in the past 10 years?
At the end of the Second World War, in an address to the Japanese people after the atomic bombing of Hiroshima and Nagasaki, the Japanese emperor [known as Showa in Japan, Hirohito in the West] used the phrase “The situation has developed not necessarily to our advantage”, and I believe we can apply that to supersymmetry. In 2006 I published a paper where I said explicitly I did not expect the Large Hadron Collider (LHC) to detect supersymmetry. It was a back-of-the-envelope calculation, where I was looking at the issue of anomalous magnetic moments. Because the magnetic moments can be sensitive to particles you can’t actually detect, by looking at the anomalous magnetic moment and then comparing the measured value to what is predicted by all the particles that you know, you can put lower bounds on the particles that you don’t know, and that’s what I did to come up with this number.
It looked to me like the lightest “superpartner” was probably going to be in the range of 30 Tev. The LHC’s initial operations were at 7 TeV and it’s currently at 14 TeV, so I’m feeling comfortable about this issue. If it’s not found by the time we reach 100 Tev, well, I’m likely going to kick the bucket by the time we get that technology. But I am confident that SUSY is out there in nature for reasons of quantum stability.
Also, observations of particle physics – particularly high-precision observations, magnetic moments, branching ratios, decay rates – are not the only way to think about finding supersymmetry. In particular, one could imagine that within string theory, there might be cosmological implications (arXiv:1907.05829), which are mostly limited to the question of dark matter and dark energy. When it comes to the dark-matter contribution in the universe, if you look at the mathematics of supersymmetry, you can easily find that there are particles that we haven’t observed yet and these might be the lightest supersymmetric particle.
And the final thing in your bucket list, which you’ve touched on, was superstring theory. When we last spoke, you said that you did not expect to see it. How has that changed, if at all?
Unless I’m blessed with a life as long as Methuselah, I don’t expect to see that. I think that for superstring theory to win observational acceptance, it will likely come about not from a single experiment, but from a confluence of observations of the cosmology and astrophysics type, and maybe then the lightest super symmetric particle will be found. By the way, I don’t expect extra dimensions ever to be found. But if I did have several hundred years to live, those are the kinds of likely expectations I would have.
And have you added anything new to your bucket list over the past 10 years?
Yes, but I don’t quite know how to verbalize it. It has to do with a confluence of things around quantum mechanics and information. In my own research, one of the striking things about the graphs that we developed to understand the representation theory of supersymmetry –we call them “adinkras” – is that error-correcting codes are part of these constructs. In fact, for me this is the proudest piece of research I’ve ever enabled – to discover a kind of physics law, or at least the possibility of a physics law, that includes error-correcting codes. I know of no previous example in history where a law of physics includes error-correcting codes, but we can clearly see it in the mathematics around these graphs (arXiv:1108.4124).
That had a profound impact on the way I think about information theory. In the 1980s, John Wheeler came up with this very interesting way to think about quantum mechanics (“Information, physics, quantum: the search for links” Proc. 3rd Int. Symp. Foundations of Quantum Mechanics, Tokyo, 1989, pp354–368). A shorthand phrase to describe it is “it from bit” – meaning that the information that we see in the universe is somehow connected to bits. As a young person, I thought that was the craziest thing I had ever heard. But in my own research I saw that it’s possible for the laws of physics to contain bits in the form of error-correcting codes, so I had to then rethink my rejection of what I thought was a wild idea.
In fact, now that I’m old, I’ve concluded that if you do theoretical physics long enough, you too can become crazy – because that’s what sort of happened to me! In the mathematics of supersymmetry, there is no way to avoid the presence of error-correcting codes and therefore bits. And because of that my new item for the bucket list is an actual observational demonstration that the laws of quantum mechanics entail the use of information in bits.
In terms of when we might see that, it will be long after I’ve gone. Unless I somehow get another 150 years of life. Intellectually, that’s how long I would estimate it will take as of now, because the hints are so stark, they suggest something is definitely going on.
We’ve talked a little bit about how science has changed in the past 10 years. Of course, science is not unconnected with the rest of the world. There have been some changes in other things that impinge on science, particularly those recently developing in the US. What’s your take on that?
Unfortunately, it’s been very predictable. Two years ago I wrote an essay called “Expelled from the mountain top?” (Science 380 993). I took that title from a statement by Martin Luther King Jr where he says “I’ve been to the mountaintop”, and the part about being “expelled” refers to closing down opportunities for people of colour. In my essay I talked about the fact that it looked to me like the US was moving in a direction where it would be less likely that people like me – a man of colour, an African American, a scientist – would continue to have access to the kind of educational training that it takes to do this [science].
I’m still of the opinion that the 2023 decision the Supreme Court made [about affirmative action] doesn’t make sense. What it is saying is that diversity has no role in driving innovation. But there’s lots of evidence that that’s not right. How do you think cities came into existence? They are places where innovation occurs because you have diverse people coming to cities.
You add to that the presence of a new medium – the Internet – and the fact that with this new medium, anyone can reach millions of people. Why is this a little bit frightening? Well, fake news. Misinformation.
Still hopeful Jim Gates discusses his career and his lifelong interest in supersymmetry with an audience at the Royal College of Art in London earlier this year. (Courtesy: Margaret Harris)
I ran into a philosopher about a year ago, and he made a statement that I found very profound. He said think of the printing press. It allowed books to disseminate through Western European society in a way that had never happened before, and therefore it drove literacy. How long did it take for literacy levels to increase? 50 to 100 years. Then he said, now let’s think about the Internet. What’s different about it? The difference is that anyone can say anything and reach millions of people. And so the challenge is how long it will take for our species to learn to write the Internet without misinformation or fake news. And if he’s right, that’s 100, 150 years. That’s part of the challenge that the US is facing. It’s not just a challenge for my country, but somehow it seems to be particularly critical in my country.
So what does this have to do with science? In 2005 I was invited to deliver a plenary address to the American Association for the Advancement of Science annual meeting. In that address, I made statements about science being turned off because it was clear to me, even back then in my country, that there were elements in our society that would be perfectly happy to deny evidence brought forth by scientists, and that these elements were becoming stronger.
You put this all together and it’s going to be an extraordinarily important, challenging time for the continuation of science because, certainly at the level of fundamental science, this is something that the public generally has to say “Yes, we want to invest in this”. If you have agencies and agents in society denying vaccines, for example, or denying the scientific evidence around evolution or climate change, if this is going to be something that the public buys into, then science itself potentially can be turned off, and that’s the thing I was warning about in 2005.
What are some practical things that members of the scientific community can do to help prevent that from happening?
First of all, come down from the ivory tower. I’ve been a part of some activities, and they normally are under the rubric of restoring the public’s trust in science, and I think that’s the wrong framing. It’s the public faith in science that’s under attack. So from my perspective, that’s what I’d much rather have people really thinking about.
What would you say the difference is between having trust in science and having faith in science?
In my mind, if I trust something, I will listen. If I have faith in something, I will listen and I will act. To me, this is a sharp distinction.
Personally, even though I expect that it’s going to be really hard going forward, I am hopeful. And I would urge young people never to lose that hope. If you lose hope, there is no hope. It’s just that simple. And so I am hopeful. Even though people may take my comments as “oh, he’s just depressed” – no, I’m not. Because I’m a scientist, I believe that one must, in a clear-eyed, hard-headed manner, look at the evidence that’s in front of us and not sentimentally try to dodge what you see, and that’s who I am. So I am hopeful in spite of all the things that I’ve just said to you.
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