From Orion to Cassiopeia

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abcstarstuff:

Feynman’s double-slit experiment brought to life

The precise methodology of Richard Feynman’s famous double-slit thought-experiment – a cornerstone of quantum mechanics that showed how electrons behave as both a particle and a wave – has been followed in full for the very first time.

Although the particle-wave duality of electrons has been demonstrated in a number of different ways since Feynman popularised the idea in 1965, none of the experiments have managed to fully replicate the methodology set out in Volume 3 of Feynman’s famous Lectures on Physics.

“The technology to do this experiment has been around for about two decades; however, to do a nice data recording of electrons takes some serious effort and has taken us three years,” said lead author of the study Professor Herman Batelaan from the University of Nebraska-Lincoln.

“Previous double-slit experiments have successfully demonstrated the mysterious properties of electrons, but none have done so using Feynman’s methodology, specifically the opening and closing of both slits at will and the ability to detect electrons one at a time.

“Akira Tonomura’s brilliant experiment used a thin, charged wire to split electrons and bring them back together again, instead of two slits in a wall which was proposed by Feynman. To the best of my knowledge, the experiments by Guilio Pozzi were the first to use nano-fabricated slits in a wall; however, the slits were covered up by stuffing them with material so could not be open and closed automatically.”

In their experiments, which have been published today, Thursday 14 March, in the Institute of Physics and German Physical Society’s New Journal of Physics, Batelaan and his team, along with colleagues at the Perimeter Institute of Theoretical Physics, created a modern representation of Feynman’s experiment by directing an electron beam, capable of firing individual electrons, at a wall made of a gold-coated silicon membrane.

The wall had two 62-nm-wide slits in it with a centre-to-centre separation of 272 nm. A 4.5 µm wide and 10 µm tall moveable mask, controlled by a piezoelectric actuator, was placed behind the wall and slid back and forth to cover the slits.

“We’ve created an experiment where both slits can be mechanically opened and closed at will and, most importantly, combined this with the capability of detecting one electron at a time.

“It is our task to turn every stone when it comes to the most fundamental experiments that one can do. We have done exactly that with Feynman’s famous thought-experiment and have been able to illustrate the key feature of quantum mechanics,” continued Batelaan.

Feynman’s double-slit experiment

In Feynman’s double-slit thought-experiment, a specific material is randomly directed at a wall which has two small slits that can be opened and closed at will – some of the material gets blocked and some passes through the slits, depending on which ones are open.

Based on the pattern that is detected beyond the wall on a backstop – which is fitted with a detector – one can discern whether the material coming through behaves as either a wave or particle.

When particles are fired at the wall with both slits open, they are more likely to hit the backstop in one particular area, whereas waves interfere with each other and hit the backstop at a number of different points with differing strength, creating what is known as an interference pattern.

In 1965, Feynman popularised that electrons – historically thought to be particles – would actually produce the pattern of a wave in the double-split experiment.

Unlike sound waves and water waves, Feynman highlighted that when electrons are fired at the wall one at a time, an interference pattern is still produced. He went on to say that this phenomenon “has in it the heart of quantum physics [but] in reality, it contains the only mystery.”

(via subatomiconsciousness)

sciencesoup:

Artificial Dust Devils

The word ‘tornado’ is usually associated with death and destruction, but mechanical engineers Mark Simpson and Ari Glezer at the Georgia Institute of Technology have figured out a way to harness them for renewable energy. They’re not out braving huge natural tornadoes, but rather they’re artificially creating small, controlled vortexes and using them to produce cheap, renewable energy. After seeing dust devils in Arizona sparked the idea, Glezer and Simpson built a metre-wide prototype that looks a bit like the inside of an aircraft engine rotor. Called the Solar Vortex, it relies on the temperature difference between hot air near the ground and cooler air just a metre above it. When the hot air rises and the cool air descends, convection currents form between the layers (convection currents are basically the continual cycle of heat transfer up and down). Well-positioned vanes force the airflow to spontaneously form into a vortex, which sucks in more warm air to maintain itself and turns a turbine at the centre of the device, generating energy—and no power is needed to kick-start it. The Department of Energy’s Advanced Research Projects Agency have agreed to fund large-scale trials, and they hope to build a 10 kilowatt model within two years and a 50 kilowatt model in the future. Glezer estimates that a square kilometre array of the turbines would produce 16 megawatts of energy—much more than the 3 to 5 megawatts of conventional wind turbines. It would be 20% cheaper than traditional wind power generation and 65% cheaper than solar panels, and the Solar Vortex doesn’t even need to be elevated to catch the wind, so it could be installed on building and factory rooftops where sufficient waste heat escapes.

(Image Credit: 1, 2)

ikenbot:

Gemini Missions

On May 25, 1961, three weeks after Mercury astronaut Alan Shepard became the first American in space, President John F. Kennedy announced the goal of sending astronauts to the moon before the end of the decade.

To facilitate this goal, NASA expanded the existing manned space flight program in December 1961 to include the development of a two-man spacecraft. The program was officially designated Gemini on January 3, 1962.

More Content: Amazing Archive of High-Res Photos from NASA’s Gemini Missions

(via subatomiconsciousness)

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