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Describing the very ‘beginning’ of the Universe is a bit of a problem. Quite simply, none of our scientific theories are up to the task. We attempt to understand the evolution of space and time and all the mass and energy within it by applying Albert Einstein’s general theory of relativity. This theory works extraordinarily well. But when we’re dealing with objects that start to approach the infinitesimally small – elementary particles such as quarks and electrons – we need to reach for a completely different structure, called quantum theory.

The post Where did all the antihadrons go? appeared first on OUPblog.

They might be short-lived — but between the time a bubble is born (Fig 1 and Fig 2a) and pops (Fig 2d-f), the bubble can interact with surrounding particles and microorganisms. The consequence of this interaction not only influences the performance of bioreactors, but also can disseminate the particles, minerals, and microorganisms throughout the atmosphere. The interaction between microorganism and bubbles has been appreciated in our civilizations for millennia, most notably in fermentation. During some of these metabolic processes, microorganisms create gas bubbles as a byproduct. Indeed the interplay of bubbles and microorganisms is captured in the origin of the word fermentation, which is derived from the Latin word ‘fervere’, or to boil. More recently, the importance of bubbles on the transfer of microorganisms has been appreciated. In the 1940s, scientists linked red tide syndrome to toxins aerosolized by bursting bubbles in the ocean. Other more deadly illnesses, such as Legionnaires’ disease have been linked since.

Bubbles are formed whenever gas is completely surrounded by an immiscible liquid. This encapsulation can occur when gas boils out of a liquid or when gas is injected or entrained from an external source, such as a breaking wave. The liquid molecules are attracted to each other more than they are to the gas molecules, and this difference in attraction leads to a surface tension at the gas-liquid interface. This surface tension minimizes surface area so that bubbles tend to be spherical when they rise and rapidly retract when they pop.

When microorganisms are near a bubble, they can interact in several ways. First, a rising bubble can create a flow that can move, mix, and stress the surrounding cells. Second, some of the gas inside the bubble can dissolve into the surrounding fluid, which can be important for respiration and gas exchange. Microorganisms can likewise influence a bubble by modifying its surface properties. Certain microorganisms secrete surfactant molecules, which like soap move to the liquid-gas interface and can locally lower the surface tension. Microorganisms can also adhere and stick on this interface. Thus, a submerged bubble travelling through the bulk can scavenge surrounding particulates during its journey, and lift them to the surface.

When a bubble reaches a surface (Figure 2c), such as the air-sea interface, it creates a thin, curved film that drains and eventually pops. In Figure 3, a sequence of images shows a bubble before (Fig 3a), during, and after rupture (Fig 3b). The schematic diagrams displayed in Fig 2c-f complement this sequence. Once a hole nucleates in the bubble film (Fig 2d), surface tension causes the film to rapidly retract and centripetal acceleration acts to destabilize the rim so that it forms ligaments and droplets. For the bubble shown, this retraction process occurs over a time of 150 microseconds, where each microsecond is a millionth of a second. The last image of the time series shows film drops launching into the surrounding air. Any particulates that became encapsulated into these film droplets, including all those encountered by the bubble on its journey through the water column, can be transported throughout the atmosphere by air currents.

Another source of droplets occurs after the bubble has ruptured (Fig 3b). The events occurring after the bubble ruptures is presented in the second time series of photographs. Here the time between photographs is one milliseconds, or 1/1000^th of a second. After the film covering the bubble has popped, the resulting cavity rapidly closes to minimize surface area. The liquid filling the cavity overshoots, creating an upward jet that can break up into vertically propelled droplets. These jet drops can also transport any nearby particulates, also including those scavenged by the bubble on its journey to the surface. Although both film and jet drops can vary in size, jet drops tend to be bigger.

Whether it is for the best or the worst, bubbles are ubiquitous in our everyday life. They can expose us to diseases and harmful chemicals, or tickle our palate with fresh scents and yeast aromas, such as those distinctly characterizing a glass of champagne. Bubbles are the messenger that can connect the depth of the waters to the air we breathe and illustrate the inherent interdependence and connectivity that we have with our surrounding environment.

The post The life of a bubble appeared first on OUPblog.

        

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On 4 July 2012, scientists at CERN’s Large Hadron Collider (LHC) facility in Geneva announced the discovery of a new elementary particle they believe is consistent with the long-sought Higgs boson, or ‘god particle’. Our understanding of the fundamental nature of matter — everything in our visible universe and everything we are — is about to take a giant leap forward. So, what is the Higgs boson and why is it so important? What role does it play in the structure of material substance? We’re celebrating the release of Higgs: The Invention and Discovery of the ‘God Particle’ with a series of posts by science writer Jim Baggott over the next week to explain some of the mysteries of the Higgs.

By Jim Baggott

We know that the physical universe is constructed from elementary matter particles (such as electrons and quarks) and the particles that transmit forces between them (such as photons). Matter particles have physical characteristics that we classify as fermions. Force particles are bosons.

In quantum field theory, these particles are represented in terms of invisible energy ‘fields’ that extend through space. Think of your childhood experiences playing with magnets. As you push the north poles of two bar magnets together, you feel the resistance between them grow in strength. This is the result of the interaction of two invisible, but nevertheless very real, magnetic fields. The force of resistance you experience as you push the magnets together is carried by invisible (or ‘virtual’) photons passing between them.

Matter and force particles are then interpreted as fundamental disturbances of these different kinds of fields. We say that these disturbances are the ‘quanta’ of the fields. The electron is the quantum of the electron field. The photon is the quantum of the electromagnetic field, and so on.

In the mid-1960s, quantum field theories were relatively unpopular among theorists. These theories seemed to suggest that force carriers should all be massless particles. This made little sense. Such a conclusion is fine for the photon, which carries the force of electromagnetism and is indeed massless. But it was believed that the carriers of the weak nuclear force, responsible for certain kinds of radioactivity, had to be large, massive particles. Where then did the mass of these particles come from?

In 1964, four research papers appeared proposing a solution. What if, these papers suggested, the universe is pervaded by a different kind of energy field, one that points (it imposes a direction in space) but doesn’t push or pull? Certain kinds of force particle might then interact with this field, thereby gaining mass. Photons would zip through the field, unaffected.

One of these papers, by English theorist Peter Higgs, included a footnote suggesting that such a field could also be expected to have a fundamental disturbance — a quantum of the field. In 1967 Steven Weinberg (and subsequently Abdus Salam) used this mechanism to devise a theory which combined the electromagnetic and weak nuclear forces. Weinberg was able to predict the masses of the carriers of the weak nuclear force: the W and Z bosons. These particles were found at CERN about 16 years later, with masses very close to Weinberg’s original predictions.

By about 1972, the new field was being referred to by most physicists as the Higgs field, and its field quantum was called the Higgs boson. The ‘Higgs mechanism’ became a key ingredient in what was to become known as the standard model of particle physics.

Jim Baggott is author of Higgs: The Invention and Discovery of the ‘God Particle’ and a freelance science writer. He was a lecturer in chemistry at the University of Reading but left to pursue a business career, where he first worked with Shell International Petroleum Company and then as an independent business consultant and trainer. His many books include Atomic: The First War of Physics (Icon, 2009), Beyond Measure: Modern Physics, Philosophy and the Meaning of Quantum Theory (OUP, 2003), A Beginner’s Guide to Reality (Penguin, 2005), and A Quantum Story: A History in 40 Moments (OUP, 2010). Read his previous blog post “Putting the Higgs particle in perspective.”

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By Frank Close To readers of Neutrino, rest assured: there is no need yet for a rewrite based on news that neutrinos might travel faster than light. I have already advertised my caution in The Observer, and a month later nothing has changed. If anything, concerns about the result have increased.

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By Frank Close

Ray Davis was the first person to look into the heart of a star. He did so by capturing neutrinos, ghostly particles that are produced in the centre of the Sun and stream out across space. As you read this, billions of them are hurtling through your eyeballs at almost the speed of light, unseen.

Neutrinos are as near to nothing as anything we know, and so elusive that they are almost invisible. When Davis began looking for solar neutrinos in 1960, many thought that he was attempting the impossible. It nearly turned out to be: 40 years would pass before he was proved right, leading to his Nobel Prize for physics in 2002, aged 87.

In June 2006, I was invited by The Guardian newspaper to write his obituary. An obituary necessarily focuses on the one person, but the saga of the solar neutrinos touched the lives of several others, scientists who devoted their entire careers chasing the elusive quarry, only to miss out on the Nobel Prize by virtue of irony, chance, or, tragically, by having already died.

Of them all, the most tragic perhaps is the genius Bruno Pontecorvo.

Pontecorvo was a remarkable scientist and a communist, working at Harwell after the war. When his Harwell colleague Klaus Fuchs was exposed as an atom spy in 1950, Pontecorvo immediately fled to the USSR. This single act probably killed his chances of Nobel Prizes.

In the following years, Pontecorvo developed a number of ideas that could have won him one or more Nobels. But his papers were published in Russian, and were unknown in the West until their English translations appeared up to two years later. By this time others in the USA had come up with the same ideas, later winning the Nobel Prize themselves.

Amongst his ideas, one involved an experiment which Soviet facilities could not perform. But most ironic were Pontecorvo’s insights about neutrinos.

Ray Davis had detected solar neutrinos – but not enough of them. For years, many of us involved in this area of research thought Davis’ experiment must have been at fault. But Pontecorvo had another theory which indicated that like chameleons, neutrinos changed their form en route across space from the Sun to Earth. And he was right. It took many years to prove it, but by 2000 the whole saga was completed. Davis duly won his Nobel Prize, but so many years had elapsed that Pontecorvo by then was dead.

So although my piece for The Guardian began as the life story of Ray Davis, Pontecorvo was there behind the scenes to such an extent that it became his story also. It is also the story of John Bahcall, Davis’ lifelong collaborator, who, to the surprise of many, was not included in the Nobel award.

The lives of these three great scientists were testimony to what science is all about: as Edison put it, genius is 1% inspiration and 99% perspiration.

A final sobering thought to put our human endeavors in context: those neutrinos that passed through you when you started reading this article are by now well on their way to Mars.

Frank Close OBE is Professor of Physics at Oxford Univeristy and a Fellow of Exeter College.  He is formerly Head of the Theoretical Physics Division at the Rutherford Appleton Laboratory, and Head of Communications and Public Education at CERN. He has written several books including The Void, Antimatter, 0 Comments on Hunting the Neutrino as of 1/1/1900