Posts by: Hamish Johnston

‘Anomalous weak values’ are nonclassical, and here is the proof

The weak value of an observable A can be nonsensical

The weak value of an observable A can be nonsensical.

By Hamish Johnston

Last month we reported on a quirky paper in Physical Review Letters entitled “How the result of a single coin toss can turn out to be 100 heads” by Christopher Ferrie of the University of New Mexico and Joshua Combes of the Perimeter Institute for Theoretical Physics in Waterloo, Canada.

The paper addresses “anomalous weak values” in quantum mechanics, a phenomenon that was first identified in 1988 by Yakir Aharonov, Lev Vaidman and colleagues at Tel Aviv University. A weak value is the result of a weak measurement on a quantum system. This is done by making repeated gentle measurements on the quantum states of identical particles. The result of each measurement only has a tiny correlation to the quantum state of the particle so the wave function of the particle does not collapse into that state. However, by making the measurement on many particles, a weak value providing useful information about the state can be obtained.

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Watch Deborah Jin’s Newton lecture on ultracold gases

 

By Hamish Johnston

A few weeks ago Deborah Jin was in London to accept the 2014 Isaac Newton Medal and Prize from the Institute of Physics. As is the custom, Jin also delivered the Institute’s Newton Lecture for 2014, which was called “Ultracold gases”. This is an apt title because Jin is an undisputed master in the control and study of gases that have been cooled to temperatures within a whisker of absolute zero.

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Can the electron wave function be trapped and divided?

Divide and conquer: the Brown bubble experiment (Courtesy: Mike Cohea/Brown University)

Divide and conquer: the Brown bubble experiment. (Courtesy: Mike Cohea/Brown University)

By Hamish Johnston

Every once in a while we come across a physics story that seems very interesting – but we just don’t know what to make of it. The latest comes in the form of a press release from Brown University in the US and concerns “electron bubbles” in liquid helium.

These bubbles are about 4 nm in diameter and are formed when a free electron moves through liquid helium and repels surrounding atoms. Physicists have been studying these bubbles for decades and in the 1960s they discovered something very strange when firing electrons across a tank of liquid helium and measuring the time it takes the bubbles to reach a detector on the other side.

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Strange goings on at CERN, string theory with cats, Isaac Asimov on generating new ideas and more

Bygone era: when 3D visualization really was 3D (Courtesy: CERN)

Bygone era: when 3D visualization really was 3D. (Courtesy: CERN)

By Hamish Johnston

“The past is a foreign country: they do things differently there,” is probably the only famous sentence written by the English novelist L P Hartley. It also sums up nicely a collection of photographs of CERN in the 1960s and early 1970s showing among other things a jolly worker wearing a beret, scientists wearing white lab coats and ties, and a strange religious-like procession. There are also lots of photos of vintage kit, including one of those huge vacuum-valve-powered oscilloscopes (probably from Tektronix) that would be familiar to physicists of a certain age. My favourite photo is shown above. It was taken in 1965, when 3D data visualization was actually done in 3D! I believe that the collection was put together by CERN’s Alex Brown and you can enjoy looking at all 55 images in the collection here.

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Candy corn in space, compact fusion reactors and physics in Palestine

 

By Hamish Johnston

Besides the great views of the Earth, one of the best things about being on the International Space Station (ISS) must be messing around in near-zero gravity. In the above video on Science Friday the American astronaut Don Pettit describes an “experiment” that he did on the ISS using candy corn, which are kernel-like sweets. He begins with a blob of floating water into which he inserts the candy corn pointy-end first. The points are hydrophilic so they tend to stay in the water, and eventually Pettit has a sphere of candy corn packed around the water. The flat ends of the candy corn have been soaked in oil to make them hydrophobic so the candy corn layer acts like a detergent film or one half of a cell membrane. It’s a fun video and I wonder how he got the idea in the first place?

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What type of physics should you do if you want to bag a Nobel prize?

Noble physics infographic

Prize-winning physics explored in our infographic created by Paul Matson.

By Hamish Johnston

Update on 16 October 2014: The 2014 prize has been added to the infographic.

At 11.45 a.m. CET (at the earliest) on Tuesday 7 October, the winner(s) of the 108th Nobel Prize for Physics will be announced in Stockholm. Like just about everyone else, I have no information about who will win – although I do have my suspicions (more on those tomorrow).

Predicting the future is never easy, but help is at hand with a new infographic that Physics World has created charting the history of the physics Nobel by discipline. Using the categories that we apply to articles on physicsworld.com, we have split the 107 prizes since 1901 into seven categories. If you click on the image above, you can see the infographic in all its glory.

The most popular discipline with Nobel committees through the ages is nuclear and particle physics, which accounts for nearly one-third of the prizes. As well as dominating the prizes in the 1950s and 1960s, nuclear and particle physics spreads its tentacles from the very first prize – to Wilhelm Röntgen for the discovery of X-rays – to last year’s prize, which went to François Englert and Peter Higgs for predicting a much more esoteric boson.

Interestingly, that very first prize in 1901 flags up an important challenge I faced while categorizing the prizes using contemporary disciplines. You could argue that when Röntgen discovered X-rays, he was doing atomic physics. Indeed, some of those X-rays would have come from atomic processes, while others would have been bremsstrahlung – which I would consider particle physics. However, because Röntgen accelerated electrons into a target and analysed the radiation produced, I decided that it was a particle-physics experiment.

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The pin-up of particle physics, an octopus-inspired robot and Witten versus Horgan redux

 

By Hamish Johnston

One of my favourite radio programmes is The Life Scientific, in which the physicist Jim Al-Khalili talks to leading scientists about their lives and work. Al-Khalili introduces this week’s guest as “the pin-up of particle physics”, whose remarkable career has taken him from playing keyboards in pop bands, to winning a Royal Society University Research Fellowship to do particle physics, to hosting one of the BBC’s most popular science programmes.

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The birthday party goes on at CERN

Sorry, you missed this concert by the UN Symphony Orchestra on 19 October, but there is more music coming up (Courtesy: CERN)

Sorry, you missed this concert by the UN Symphony Orchestra on 19 September, but there is more music coming up. (Courtesy: CERN)

By Hamish Johnston

All this week the people at CERN and in its member states will be celebrating 60 years of particle physics at the world-famous lab in Geneva. There is something for everyone to enjoy and here are a few highlights that we have picked out

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A scientific pyramid scheme, symmetry through the ages, why physics students are “standing a little taller” and more

Pyramid power: this lovely pyramid has nothing to do with postdocs. It is model of a much larger  Sierpinski tree that can be found on London’s South Bank.

Pyramid power: this lovely object has nothing to do with postdocs. It is a simpler version of a much larger Sierpinski tree that can be found on London’s South Bank.

By Hamish Johnston

Just this week six people were convicted in Bristol of crimes related to running a pyramid scheme. This involves taking money from lots of new investors and giving it to a smaller number of investors who signed up earlier – until the pyramid collapses. Is the current model for training scientists a pyramid scheme of sorts? That is the claim in a piece on the US’s National Public Radio (NPR) website written by Richard Harris.

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The secret life of hairdryers, the crackpot conundrum and mesmerizing animations

By Hamish Johnston

Secret lives will be revealed at the Science Museum in London (Courtesy: Batholith)

Its secret life will be revealed at the Science Museum in London. (Courtesy: Batholith)

If you happen to be in London next Saturday (20 September), the Science Museum is running a workshop called “The field life of electronic objects”. Participants will measure the electromagnetic fields surrounding everyday objects such as hairdryers and hard drives “to produce astonishing light images of these objects’ secret life”. Space is limited, the cost is £10 and you can register online.

One thing that we really struggle with here at physicsworld.com is comments from crackpots. My colleagues and I put a lot of effort into writing and editing articles that we believe will be of general interest to the physics community. There is nothing more soul-destroying than spending hours trying to understand and then explain a tricky piece of research only to see the comments on your article hijacked by someone promoting their own bizarre theory.

The American Physical Society (APS) takes a brave and novel way of dealing with crackpots – it gives them their own sessions at APS conferences. In “The Crackpot Conundrum”, blogger Henry Brown describes the mood at such sessions as depressing, something that I understand based on a session that I sat through. Brown then reviews some of the various ways that physics bloggers deal with crackpots and in a moment of deep introspection suspects that he might be seen by some as a crackpot!

Finally, if you are winding down on a Friday afternoon, you can put yourself in a trance by watching these mesmerizing animations by the Irish physicist David Whyte.

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