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Category: particle physics

A new form of light has been discovered by physicists from Trinity College Dublin’s School of Physics and the CRANN Institute, Trinity College, which will impact our understanding of the fundamental nature of light.

One of the measurable characteristics of a beam of light is known as angular momentum, The Spectrum reports. Until now, it was thought that in all forms of light the angular momentum would be a multiple of Planck’s constant (the physical constant that sets the scale of quantum effects).

Now, recent PhD graduate Kyle Ballantine and Professor Paul Eastham, both from Trinity College Dublin’s School of Physics, along with Professor John Donegan from CRANN, have demonstrated a new form of light where the angular momentum of each photon (a particle of visible light) takes only half of this value. This difference, though small, is profound. These results were recently published in the online journal Science Advances.

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Whether these Universes are similar or different to our own, whether they have the same physical laws and properties, whether they have the same fundamental constants, particles and interactions, we do not know.

And at the same time, our very best laws of nature tell us that this is reality: we are a tiny fraction of our observable Universe, which is a tiny bit of the unobservable Universe, which is just one of a tremendous number of Universes in a multiverse that’s constantly generating new ones, and has been for billions of years. And that’s the Multiverse we live in, to the best of our knowledge!

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Abstract: Physicists at the Swiss Nanoscience Institute and the University of Basel have succeeded in measuring the very weak van der Waals forces between individual atoms for the first time. To do this, they fixed individual noble gas atoms within a molecular network and determined the interactions with a single xenon atom that they had positioned at the tip of an atomic force microscope. As expected, the forces varied according to the distance between the two atoms; but, in some cases, the forces were several times larger than theoretically calculated. These findings are reported by the international team of researchers in Nature Communications.

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In the late 1990s, astronomers discovered something mysterious pushing galaxies apart faster than gravity pulls them together. It seemed like every little bit of space had some amount of energy that spread it away from every other little bit of space, and that strange pushing came to be known as ‘dark energy’ — dark, because no one knows what it is.

And now a group of physicists have shown that dark energy could probably be explained — as long as we’re willing to give up a fundamental piece of our understanding of light…

Most scientists think that dark energy exists because of what’s known as a cosmological constant — something acting throughout the Universe that tells different bits of space to repel each other. It’s sort of like an anti-gravity force, but it acts everywhere instead of just being between two things with mass and it always acts with the same strength.

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I am told by a TOTEM manager that this is public news and so it can be blogged about — so here I would like to explain a rather cunning plan that the TOTEM and the CMS collaborations have put together to enhance the possibilities of a discovery, and a better characterization, of the particle that everybody hopes is real, the 750 GeV resonance seen in photon pairs data by ATLAS and CMS in their 2015 data.

What is TOTEM, first of all? Well, TOTEM is a collaboration that operates some high-rapidity detectors located around the CMS collision point at the LHC. And before you ask, rapidity is a measurement of how close to the beam a particle is emitted by a collision. Particles emitted orthogonally have rapidity equal to zero; particles traveling at angles increasingly close to the z axis (which we take to be the beam axis at the collision point) have higher positive or negative rapidity (the sign depends on the verse, and is determined by convention). Below is a schematic of the detector.

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Flick a switch on a dark winter day and your office is flooded with bright light, one of many everyday miracles to which we are all usually oblivious.

A physicist would probably describe what is happening in terms of the particle nature of light. An atom or molecule in the fluorescent tube that is in an excited state spontaneously decays to a lower energy state, releasing a particle called a . When the photon enters your eye, something similar happens but in reverse. The photon is absorbed by a molecule in the retina and its energy kicks that molecule into an excited state.

Light is both a particle and a wave, and this duality is fundamental to the physics that rule the Lilliputian world of atoms and . Yet it would seem that in this case the wave nature of light can be safely ignored.

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A documentary film just had its premiere at the Hot Docs festival in Toronto. How To Build A Time Machine, the work of filmmaker Jay Cheel, is a strange and incoherent little document of two middle-aged men with loosely related obsessions: One of them wants to build a perfect recreation of a movie prop – the machine from the 1960 movie The Time Machine, based on the H.G. Wells novel – and the other is a theoretical physicist who thinks he may have effected a kind of time travel in a lab, on a microscopic scale, using lasers that push particles around. The weak connection between the two men is that they both regret a death in their past – a best friend, a father – and are preoccupied with what they might have done to prevent the death; they both wonder if time travel to the past might have been a remedy for death itself. (Compared to the protagonist of Zero K who seeks immortality as a way of avoiding the loss of a loved one.) The 80s synthpop song Forever Young by Alphaville booms symbolically at one point.

Why this sudden ascendancy of yearning for immortality now? Is it simply because immortality of a medical sort might be imminent, a result of technological advances, such as nanobots, that will fight disease in our bloodstream? Or is it because, as Ray Kurzweil implies, digital technology is now so advanced that we have already left our bodies behind? We already live outside them, and our digital selves will outlive them. (“I mean,” says Kurzweil, “this little Android phone I’m carrying on my belt is not yet inside my physical body, but that’s an arbitrary distinction.”)

The frequently quoted axiom of Arthur C. Clarke – “Any sufficiently advanced technology is indistinguishable from magic” – is pertinent to this current fascination with life without end. We are now perceiving technology as not just magic but as god-like, as life-giving, as representing an entirely new plane of being.

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Scientists have devised a way to build a “quantum metamaterial” — an engineered material with exotic properties not found in nature — using ultracold atoms trapped in an artificial crystal composed of light. The theoretical work represents a step toward manipulating atoms to transmit information, perform complex simulations or function as powerful sensors.

The research team, led by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley, proposes the use of an accordion-like atomic framework, or “lattice” structure, made with laser light to trap atoms in regularly spaced nanoscale pockets. Such a light-based structure, which has patterned features that in some ways resemble those of a crystal, is essentially a “perfect” structure — free of the typical defects found in natural materials.

Researchers believe they can pinpoint the placement of a so-called “probe” atom in this crystal of light, and actively tune its behavior with another type of laser light (near-infrared light) to make the atom cough up some of its energy on demand in the form of a particle of light, or photon.

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A strange new behavior of water molecules has been observed inside crystals of beryl, a type of emerald, caused by bizarre quantum-mechanical effects that let the water molecules face six different directions at the same time.

Under normal conditions, the two hydrogen atoms in each water molecule are arranged around the oxygen atom in an open “V” shape, sometimes compared to a boomerang or Mickey Mouse ears.

But in a new experiment, scientists have found that hydrogen atoms of some water molecules trapped in the crystal structure of the mineral beryl become “smeared out” into a six-sided ring. [T he Surprisingly Strange Physics of Water].

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Anyone who has ever gotten, or even thought about getting a tattoo had heard a snarky warning from others about how they’re forever. Well, maybe they aren’t. A company called Ephemeral has designed a two-part system for tattoos that last about a year. It’d probably be a smart move for people who have trouble with commitment.

Traditional tattoos are permanent because the ink particles embedded in the skin are too large for the immune system to clear. Existing methods of tattoo removal with lasers essentially break the particles down until they can be easily cleared. Of course, it really, really hurts. Ephemeral has engineered a two-part system consisting of dye molecules encapsulated in a protective structure and a removal solution.

The protective coating of the dye molecules is engineered to last about one year, at which time it starts breaking down. The tattoo will begin fading rapidly at that point, though it’s not clear how long it will take to fully disappear. The removal solution can be added to the skin at any time by a tattoo machine over top of the Ephemeral tattoo to instantly break down the coating and “erase” parts or all of a tattoo.

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