EXPeditions

Harry Cliff - The Higgs boson, dark matter and other mysteries of the universe

The Higgs boson is so important to our understanding of particle physics that it was hyperbolically referred to as the “God Particle”.
About Harry Cliff
"I am a particle physicist at the University of Cambridge, a populariser of science and a science writer.
I work on an experiment called LHCb, which is a giant particle detector on the Large Hadron Collider at CERN, where we study elementary particles – the basic building blocks of our universe."
When protons collide
I work on the Large Hadron Collider, which is the world’s largest particle collider. What it does is simple and brutal. It takes particles called protons and smashes them into one another with lots of energy.
There’s a long tradition in particle physics of these sorts of experiments where you smash particles into one another. The reason for doing this is perhaps not what you would expect. Particle colliders are sometimes described as atom smashers, which conveys the idea that we’re using these machines to smash atoms apart to see what’s inside them. But that’s not really what colliders are for, because we know what’s inside atoms. We discovered that in the 20th century.
Colliders like the Large Hadron are better described as matter factories. You accelerate particles to very high speeds because, at those speeds, particles carry huge amounts of energy. When you collide them, that kinetic energy is converted into new matter. So, you’re actually making matter or making new particles from energy. When two protons collide, many of the particles coming out of that collision didn’t exist before; they were created in the collision.
In other words, this is a way of studying the sorts of objects that can exist in the universe. When you get to really high energies, you’re probing energy densities, temperatures and conditions that haven’t existed in the universe in any large amounts since about a trillionth of a second after the Big Bang. You’re probing the kinds of things that were going on in the very first moments of the universe. This is why these experiments are so interesting.
Key Points
• July, 4th 2012 was a pivotal day in the history of particle physics. At a special event, scientists working at the Large Hadron Collider confirmed they had detected the Higgs boson.• The Higgs boson interacts with a quantum field known as the Higgs field, giving mass to particles like electrons and quarks. Without this interaction, electrons and quarks would never bind together to form stable atoms.• While the Higgs is the last missing piece of the Standard Model, it opens up a whole new set of questions and problems for particle physicists to puzzle over.

Keith Moffatt - Stars, Planets and Galaxies?

Keith Moffat, Emeritus Professor of Mathematical Physics at the University of Cambridge, addresses magnetic field generation.
About Keith Moffatt
"I’m Emeritus Professor of Mathematical Physics at the University of Cambridge and a Fellow of Trinity College, Cambridge.
My research field is fluid mechanics in all its aspects, ranging from the micro scale, applicable to biological fluid mechanics in particular, to the macro scale interaction with magnetic fields, with relevance to planets, stars and galaxies."
A complex interaction
My own involvement in astrophysics started when I was a PhD student. My thesis topic was the interaction of turbulence with magnetic fields. That involves both the Navier–Stokes equations and Maxwell’s equations for the electromagnetic field, and the very strong interaction between these topics in electrically conducting fluids. When you have currents flowing in these fluids, magnetic fields result, and the interaction of currents and magnetic fields affect the fluid motion. So, it becomes a very complex interaction. My own involvement has been primarily in the field known as dynamo theory, explaining the origin of magnetic fields and the way they evolve in planets, stars and even galaxies.
Key Points
• My thesis topic was the interaction of turbulence with magnetic fields. That involves both the Navier–Stokes equations and Maxwell’s equations for the electromagnetic field, and the very strong interaction between these topics in electrically conducting fluids.• A bootstrap effect, or a magnetic instability, gives rise to the generation of the magnetic field of the Earth.• Without the magnetic field of the Earth, we would be subject to extremely harmful radiation. It’s doubtful whether any of us could survive that radiation.

Sara Seager - Finding a planet like Earth

When I think of an Earth-like exoplanet, I think of a planet with oceans, continents and a friendly atmosphere. In short, a planet like Earth orbiting a star like our own sun.
About Sara Seager 
"I’m an astrophysicist and professor at the Massachusetts Institute of Technology and Kavli Prize in Astrophysics, 2024.
My research focuses on exoplanets, planets which orbit stars other than our sun. My quest is to find another Earth, a true ‘Earth twin’, and to search for signs of life on any kind of exoplanet by studying their atmospheres. I’ve played a leadership role on space missions, and I’m also working for new, more sophisticated ways to find planets."
Searching for a second home
When I think of an Earth-like exoplanet, I think of a planet with oceans, continents and a friendly atmosphere. In short, a planet like Earth orbiting a star like our own sun. Currently, finding the so-called Earth twin seems unlikely to occur soon.
After all, most of our attention in astronomy is focused on small stars rather than more prominent sun-like stars. This is because finding a planet suitable for life orbiting these smaller stars is much easier. We think of these potential planets more like an Earth cousin than like an Earth twin.
Regardless, finding a planet like Earth could actually happen at any time. We have maybe a dozen candidates we're just waiting to observe with the James Webb Space Telescope or JWST. The next generation of large, ground-based telescopes will also help find and characterise more planets and determine if they are anything like Earth.
Key Points
• Nearby planets like Proxima Centauri b and Kepler-186f may receive enough energy and have other conditions suitable for life.• Observing Earth-like planets is challenging. It requires sophisticated telescopes to be sent into space beyond the atmosphere's blurring effect.• The brightness of host stars also makes planets challenging to observe. Starshade, a specially designed screen, may help identify Earth-like planets by blocking light.

Sara Seager - Modern telescopes and exoplanets

We hope that understanding how planets form and the kinds of planets will help us better understand Earth, our solar system and our role here.
About Sara Seager 
"I’m an astrophysicist and professor at the Massachusetts Institute of Technology and Kavli Prize in Astrophysics, 2024.
My research focuses on exoplanets, planets which orbit stars other than our sun. My quest is to find another Earth, a true ‘Earth twin’, and to search for signs of life on any kind of exoplanet by studying their atmospheres. I’ve played a leadership role on space missions, and I’m also working for new, more sophisticated ways to find planets."
Our place in the universe
Humans are born explorers. We are driven to understand our universe and why we are here. The search for exoplanets encompasses both of these themes. We hope that understanding how planets form and the kinds of planets will help us better understand Earth, our solar system and our role here.
When astronomers began searching for exoplanets using the traditional tools of astronomy, they looked for copies of our solar system. It's amusing to consider how this entire paradigm of science – how planets form – had to be built upon our understanding of our solar system.

Harry Cliff - The mysteries in particle physics and fundamental physics

The most straightforward problem to explain is the mystery of dark matter.
About Harry Cliff
"I am a particle physicist at the University of Cambridge, a populariser of science and a science writer.
I work on an experiment called LHCb, which is a giant particle detector on the Large Hadron Collider at CERN, where we study elementary particles – the basic building blocks of our universe."
The enduring mystery of existence
There are many mysteries in particle physics and fundamental physics in general that we can’t answer at the moment. This is why we do experiments at the Large Hadron Collider and elsewhere.
The most straightforward problem to explain is the mystery of dark matter. We know from astronomy that there is about five times more invisible, or dark matter in the universe than ordinary matter. By ordinary matter, I mean stuff made of atoms and particles in the Standard Model of particle physics. This includes gas, dust, stars, planets and people. But all of that represents only about one-sixth of the total matter in the universe. Eighty-five per cent of the matter in the universe is this mysterious stuff called dark matter, which doesn’t interact with, reflect, emit or absorb light. We can tell it’s there from its gravitational influence on the visible universe, but we have no idea what it’s made from and there are no particles in nature that can explain what dark matter is. One of the big hopes is that either at the LHC or some other direct detection experiments underground, we might get a clue as to what the particle of dark matter is.
Perhaps the most embarrassing outstanding problem is that the Standard Model of particle physics, our best theory of the universe, tells us that the material universe should not exist. This has to do with antimatter, which you can think of as a mirror image of the ordinary matter in our universe. In the Standard Model, every particle has an "anti" version. The electron, which is negatively charged, has an "anti" version called the positron, which is positively charged. Our theories tell us that in the early universe, we should have got equal amounts of matter and antimatter created in the Big Bang. But had that happened, either there would be anti-galaxies and anti-stars out there in the universe – and we see absolutely no evidence for that – or matter and antimatter would have annihilated each other and left us with an empty universe. So, the fact that we exist is a big mystery.
Key Points
• It’s a mystery that we exist at all. According to the Standard Model, matter and antimatter should have annihilated each other in the earliest moments of the universe.• One of the goals of the Large Hadron Collider is to find new particles that may help explain why the Higgs field is so finely balanced. So far, no new particles have been discovered.• However, physicists at the LHC have encountered anomalies in their experimental results that may suggest the presence of new particles.

Sara Seager - New planets around the nearest stars

With hundreds of billions of stars in a galaxy and hundreds of billions of galaxies, there are just untold numbers of planets out there. The vastness of space is truly incomprehensible.
About Sara Seager 
"I’m an astrophysicist and professor at the Massachusetts Institute of Technology and Kavli Prize in Astrophysics, 2024.
My research focuses on exoplanets, planets which orbit stars other than our sun. My quest is to find another Earth, a true ‘Earth twin’, and to search for signs of life on any kind of exoplanet by studying their atmospheres. I’ve played a leadership role on space missions, and I’m also working for new, more sophisticated ways to find planets."
The night sky
When we look at the night sky, we can see hundreds of stars. Our Milky Way galaxy alone has hundreds of billions of stars, and the universe has hundreds of billions of galaxies. Indeed, the total number of stars is incomprehensible.
We also know that every star is a sun. Just like our sun, these stars also have planets. Indeed, astronomers have found thousands of planets orbiting other suns. With hundreds of billions of stars in a galaxy and hundreds of billions of galaxies, there are just untold numbers of planets out there. The vastness of space is truly incomprehensible.
Key Points
• The same technological developments that have improved everyday innovations like smartphones are advancing the study of astronomy.• Our nearest star, Proxima Centauri, is over four light-years – about 24 trillion miles – away. It would take the Voyager spacecraft nearly 100,000 years to reach it.• The transit method is the primary technique used in studying exoplanets. It involves measuring the drop in a star’s brightness as a planet passes in front of it.

Harry Cliff - The basic building blocks of our universe

Looking at the history of particle physics is a good way to understand what we currently know about the basic building blocks of our universe.
About Harry Cliff
"I am a particle physicist at the University of Cambridge, a populariser of science and a science writer.
I work on an experiment called LHCb, which is a giant particle detector on the Large Hadron Collider at CERN, where we study elementary particles – the basic building blocks of our universe."
The particle pioneers
Looking at the history of particle physics is a good way to understand what we currently know about the basic building blocks of our universe.
The story starts in 1897 at the Cavendish Laboratory in Cambridge, where I’m based. A scientist named Joseph John Thomson discovered the first elementary particle: the electron. His experiment used basic equipment — a glass tube pumped out of all the air through which he just passed an electric current. By manipulating these beams of particles, Thomson figured out that what was flowing through the tube were particles much lighter than the lightest known atom at the time. That’s what we now call the electron – the first elementary particle; a tiny, negatively charged particle. 1897 is really the beginning of a journey of exploration, as other scientists start to gradually unpick and dismantle the atom over the next half-century or so.
The apparatus used by Ernest Rutherford in his atom-splitting experiments, set up on a small table in the centre of his Cambridge University research room – Cavendish Laboratory. Wikimedia Commons. Public Domain.
The next major breakthrough came several decades later, in 1911, when Ernest Rutherford (who had been one of Thomson’s PhD students in the late 1890s) was working at the University of Manchester. Rutherford and his researchers Geiger and Marsden did this very famous experiment where they fired alpha particles, a type of radiation emitted by certain radioactive elements, at a thin gold foil. They discovered something very strange, which is that these alpha particles act like high-velocity bullets. You can imagine them as shells from a cannon being fired at gold atoms. Rutherford was surprised to discover that these alpha particles were occasionally getting knocked backward off the gold foil. This led him to realise that atoms have a tiny, extremely dense centre, which we call the nucleus. The nucleus, which is positively charged, contains almost all the atom’s mass, and the electrons go around it. What was happening in this experiment was that these alpha particles were occasionally coming really close to this tiny nucleus. And when they got really close, this enormous positive charge repelled them backward.
Key Points
• Pioneering scientists like Thomson and Rutherford used basic equipment to make ground-breaking discoveries such as identifying electrons and the nucleus of the atom.• Since the 1960s, scientists have used huge accelerators to create high-energy collisions between particles, which led to the discovery of quarks.• The Standard Model explains how these particles interact with one another and is one of the crowning intellectual achievements in human history.• The framework of quantum field theory allows us to understand the forces of nature, or at least three of the forces of nature.

Lauren Kassell - Astrology, one of our longest intellectual traditions

Lauren Kassell, Chair in History of Science at the European University Institute, discusses the evolution of astrology.
About Lauren Kassell
"I am Professor of History of Science and Medicine at the University of Cambridge and Chair of the History of Science at the European University Institute.
My expertise is in the history of science and medicine, particularly astrology and magic and sex and reproduction in early modern England. I love archives, paper archives and digital archives."
From the Fertile Crescent until now
Astrology is one of the longest surviving intellectual traditions in history. So, when we get to early modern Europe, it has been around from its development in Ancient Mesopotamia, through its elaboration first by the Greeks and then in the Arab world. It gets transmitted to Europe in the Middle Ages, and then becomes more and more complex in the Renaissance. The basic premise of astrology isn’t something that was complicated. It was the most straightforward thing in the world. The heavens are connected to life on Earth, and as the stars move, so life on Earth changes.
Key Points
• Astrology, a tradition that has endured since the time of Ancient Mesopotamia, was grouped together with astronomy and based on observations in the natural world.• Both the elite and the masses practised astrology, which was ubiquitous. It was studied in universities, but a university experience was not necessary to become an astrologer; apprenticeship was possible.• In the early modern period, medicine and astrology were linked, but the latter was connected with controversy.

Martin Rees - Exploring the origins of the universe

The last 50 years of astronomy have been one of the real highlights of science. I’ve been privileged to be part of this huge cosmic exploration.
About Martin Rees
"I'm the UK's Astronomer Royal and Emeritus Professor of Cosmology and Astrophysics at the University of Cambridge.
My research is mainly on trying to understand our universe around us. Aside from astronomy and space science, I’ve been very much engaged with science policy, particularly how modern technology can be controlled so that we can harness its benefits but avoid its downsides."
Why we study astronomy
I’m an astronomer, and I think there are four reasons we do astronomy. The first is simply exploration, to find out what’s out there. The second is to make sense of what we see, to understand it in terms of the laws of physics and to perhaps discover new laws of physics. The third is to understand cosmic evolution: was there a beginning, and if so, then how have things evolved from that beginning to the amazing cosmos we see around us and are a part of? And that leads to a final reason: the mystery of why things exist, and why the universe is the way it is.
All these things are part of astronomy and what I do, and of course, pure thought doesn’t get you very far. But thanks to improved instruments, we’ve made huge progress. The last 50 years of astronomy have been one of the real highlights of science, up there with the standard model of particle physics and the double helix. I’ve been privileged to be part of this huge cosmic exploration.
Key Points
• Great achievements have been made in the last 50 years of astronomy, such as the corroboration of the Big Bang and the realisation that our solar system is not unique.• We can understand what the universe was like when it was a nanosecond old, but the very first nanosecond itself is still speculative, and many key features of our universe may have been determined then.• The chemical elements in our universe are made from star explosions – we are the ashes of dead stars.

Sander van der Linden - The consequences of fake news

Sander van der Linden, Professor of Social Psychology in Society at Cambridge, explores how fake news damages all aspects of society.
About Sander van der Linden"I am a Professor of Social Psychology and Director of the Social Decision-Making Lab at the University of Cambridge.
I study the influence process, so I study how people are persuaded by information, and especially misinformation, and how we can help people resist persuasion when they don’t want to be persuaded. As part of that I’ve written a book, The Truth Vaccine: An Antidote to Fake News, where we break down the influence process."
Misinformation can be murder
We can think about the damaging consequences of misinformation and fake news both in terms of the individual and society at large.
Starting with the individual, we've seen awful things happening in the world. In India, there have been mass mob lynchings going on for years now because of false rumours and misinformation spread on WhatsApp. For example, a community might receive a false message that some kidnappers are in the area and that a child has been kidnapped, with false photos and a specific location data. Mobs will go out and attack people violently in a kind of vigilante retribution. At the end of the day, they're acting on this false information, which appears to come from a trusted source within their social network.
Key Points
• Fake news can have tragic consequences, such as the spate of lynchings in India caused by false rumours spread on WhatsApp.• Research has shown that people who believe coronavirus conspiracy theories are less likely to get vaccinated.• People are more likely to mistrust science when they think its findings restrict their personal freedom.