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How Charles Wheatstone got to see polarization


 
By Matin Durrani

Things seem to have quietened down a bit following last month’s announcement by astronomers in the BICEP2 collaboration that they had obtained the first evidence of cosmic inflation – the period of rapid expansion in the first fraction of a second after the Big Bang. As you’ll know if you’ve been keeping up, the evidence was obtained by searching for certain “B-mode” polarizations in the cosmic microwave background, which are related to primordial gravitational waves that are thought to have abounded in the early universe. These polarizations differ from “E-mode” polarization, which describes how the magnitude of polarization varies across the CMB.

But never mind your fancy B-modes and E-modes, how well do you understand the concept of polarization in the first place? Our understanding of wave polarization dates back to the 19th century. In the late 1840s Sir Charles Wheastone, who was then professor of experimental philosophy at the University of London, decided to create a mechanical device to explain the principles of the concept – several decades before James Clerk Maxwell’s theory of the electromagnetic nature of light.

The video above shows a rare surviving example of one of these “Wheatstone Wave Machines”, which has been restored to working order by Robert Whitworth and colleagues at the University of Birmingham in the UK as part of their collection of historic physics instruments. Wheatstone designed the machine to visualize the wave nature of light and offer what Whitworth calls “a vivid insight into the theoretical concepts of wave motion”. At the time, there were other devices that showed the behaviour of travelling plane waves, but Wheatstone’s was different in that it was the first to demonstrate circularly polarized light.

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Hi-tech giants eschew corporate R&D, says report

IBM's latest crop of research fellows: are big companies cutting back on fundamental research? (Courtesy: IBM)

IBM’s latest crop of research fellows: are big companies cutting back on fundamental research? (Courtesy: IBM)

By Hamish Johnston

“Think” has been motto of the US-based computer giant IBM since it was coined in the early 20th century by founder Thomas Watson. Many would argue that IBM has succeeded over the past 100 years because physicists and other scientists were given the freedom to think while working at the company’s research labs. And science has benefitted too, with three Nobel prizes won or shared by physicists working at the firm’s labs. Even more impressive is that a whopping seven physics Nobels have been awarded to physicists at Bell Labs – originally Bell Telephone Laboratories.

But the days of these corporate “idea factories” are over according to a new study published by the American Institute of Physics (AIP). Entitled Physics Entrepreneurship and Innovation (PDF), the 308-page report argues that many large businesses are closing in-house research facilities and instead buying in new expertise and technologies by acquiring hi-tech start-ups.

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3D printing food, ‘Top 10′ lists, teenage nuclear physicists and more

 

By Tushna Commissariat

Over the past few years, 3D printing has captured the imagination and interest of scientists and the public alike. Now, a €3 million EU-funded project known as “PERFORMANCE – PERsonalised FOod using Rapid MAnufacturing for the Nutrition of elderly ConsumErs” is adapting 3D printing technology to food in order to create easily digestible sustenance that is not only nutritious but also looks and tastes like the real thing. The proposed printer would work like its conventional inkjet counterpart – except the cartridges would be filled with liquefied food instead of ink! While that may not sound like the most appetising way of eating your five-a-day, it might come as a relief for those who suffer from a condition known as “dysphagia” that makes swallowing food difficult. You can read more about the proposed scheme on the EU’s Horizon magazine website and take a look at the video above.

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Setting the standard for Brazilian materials science

Brazil's standards lab, Inmetro

Long and low – Inmetro, Brazil’s standards lab.

By Michael Banks in Rio de Janeiro, Brazil

As part of my road-trip round Brazil, I visited Inmetro – the Brazilian standards lab. Located around 50 km north of Rio de Janeiro, Inmetro certainly has the feeling of being well away from the hustle and bustle of one of Brazil’s major cities.

The first thing that you notice when you enter Inmetro’s vast campus is that the buildings have a unique architecture (see above). The bunker-like structures are built in such a way that they are protected from the Sun, which can deliver 40 °C temperatures in summer. (Thankfully, I am here in autumn, but the temperature is still a warm 30 °C.)

Inmetro’s campus was built about 40 years ago with the help of the PTB – the German standards lab. The buildings were also specially designed so that the labs are vibrationally separate from the offices. So, any wild jumping around at your desk won’t affect the sensitive measurements in the lab.

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Boosting innovation in Brazil

Evaldo Ferreira Vilela

FAPEMIG boss Evaldo Ferreira Vilela.

By Michael Banks in Belo Horizonte, Brazil

I’m writing this while on a week-long road trip across Brazil to gather information for a new report that IOP Publishing, which publishes Physics World, is producing for the Brazilian Materials Research Society.

While on my trip, I have visited a number of institutes that focus on materials research. But I also had the chance to talk a bit of policy when visiting FAPEMIG – the main state funder for research in Minas Gerais, which is the second most populous state in Brazil.

In Belo Horizonte, which is the capital of Minas Gerais, I met Evaldo Ferreira Vilela, who is director of science, technology and innovation at FAPEMIG.

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Why electricity grids fail, what to do if your PhD is stolen, and what is a ‘Suris tetron’?

 

By Hamish Johnston

It’s the nightmare scenario for any PhD student: losing all those research results that you carefully squirreled away for when you finally sit down to write your thesis. That’s just what happened to biologist Billy Hinchen, who lost four years’ worth of 3D time-lapse videos of developing crustacean embryos when his laptop and back-up drives were stolen. Find out what happened next in “What would happen if you lost all of your research data?” by Julia Giddings at the scientific software firm Digital Science. Hinchen also tells his tale of woe in the video above.

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BOSS uses 164,000 quasars to map expanding universe

An artist's illustration of how BOSS uses quasars to measure the distant universe (Courtesy: Zosia Rostomian, Lawrence Berkeley National Laboratory; Andreu Font-Ribera, BOSS)

An artist’s illustration of how BOSS uses quasars to measure the distant universe. (Courtesy: Zosia Rostomian, Lawrence Berkeley National Laboratory; Andreu Font-Ribera, BOSS)

By Calla Cofield at the APS April Meeting in Savannah, Georgia

Scientists looking at data from the Baryon Oscillation Spectroscopic Survey (BOSS), the largest programme in the third Sloan Digital Sky Survey, have measured the expansion rate of the universe 10.8 billion years ago — a time prior to the onset of accelerated expansion caused by dark energy. The measurement is also the most precise measurement of a universal expansion rate ever made, with only 2% uncertainty. The results were announced at a press conference at the APS’s April meeting on Monday, at the same time that the results were posted on the arXiv preprint server.

The rate of universal expansion has changed over the course of the universe’s lifetime. It is believed to have gradually slowed down after the Big Bang, but mysteriously began accelerating again about 7 billion years ago. BOSS and other observatories have previously measured expansion rates going back 6 billion years.

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Why axing practicals from science exams is a bad idea

Science practical exams

(iStock/LuVo)

By Matin Durrani

I don’t know about you, but I look back rather nostalgically on the practical exams that I took as an 18 year old as part of my A-levels in physics and chemistry. At the time, I wasn’t looking forward to them at all – they lasted three hours each and there was always the very large possibility of completely mucking up your experiment and/or dropping all your samples on the floor.

Although I’ve forgotten everything about my physics practical exam, the chemistry practical still sticks out in my mind. I remember making some needle-like crystals that, through amazing good fortune, turned out really well – certainly far better than the watery mush I’d created in my mock exams. So when I walked over to the other side of the lab to measure the temperature at which the crystals melted, they did so over a really narrow range – and presumably at the “correct” temperature too.

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A possible dark-matter bubble

Fermi all-sky image of the gamma-ray sky

This all-sky image, constructed from two Fermi datasets, shows how the gamma-ray sky appears at energies greater than 1 GeV. (Courtesy: NASA/DOE/Fermi/LAT Collaboration)

 

By Calla Cofield at the APS April Meeting in Savannah, Georgia

The American Physical Society (APS) April meeting has been taking place in Savannah, Georgia, for the past three days. On Saturday, Tracy Slatyer from MIT spoke to reporters about a paper that she and colleagues posted on arXiv in February, in which they suggest that a mysterious excess of gamma rays surrounding the galactic centre could be explained as dark-matter particle annihilation.

The researchers use what Slatyer calls a “simple” model of dark matter, in which the invisible substance is made up of weakly interacting massive particles (WIMPs) with a mass of about 35 GeV. The model predicts that WIMPs may collide with each other and annihilate, producing gamma rays and either b-quarks or some other mixture of quarks. The Fermi Gamma-ray Space Telescope surveys the entire observable sky for the presence of gamma rays. Fermi’s observation of the plane of the Milky Way revealed that our galaxy is bright with gamma rays, but Fermi has not been able to identify the sources of all those powerful photons. Gamma-ray excesses (more than can be explained by known sources) near the galactic centre have been identified in the Fermi data in the past – most notably at about 130 GeV.

The work presented by Slatyer and her colleagues identifies an excess of gamma rays between 1 and 3 GeV. The researchers say they can see a distinctly spherical, bubble-like collection of photons. Slatyer told reporters that based on the dark-matter model, this spherical shape is not a coincidence – the dark-matter annihilation theory does not hold for a more stretched-out, elongated cluster of gamma rays; nor would it hold if the bubble were not at the centre of the galaxy.

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Cakes that are out of this world, what’s on Andre Geim’s iPod and who’s the April fool?

The joke’s on me: click on the image for a larger version where you can see the instruction for users

The joke’s on me: click on the image for a larger version where you can see the instruction for users

By Hamish Johnston

On Tuesday I was feeling particularly pleased with myself over the April Fool’s piece that I penned. It was about a fictitious microwave-oven ban organized by radio astronomers at the UK’s Jodrell Bank Observatory. But now it looks like I might have a bit of microwaved egg on my face because two of my colleagues visited Jodrell Bank this week and guess what? Astronomers there have built a Faraday cage around the microwave in their tearoom to stop it from interfering with their equipment. Louise Mayor took the above photos: click on the image to read the reminder to microwave users.

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