Posts Tagged ‘light

Albert Einstein: Why Light is Quantum

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Ever wonder what Einstein really did? He showed that light was a particle!

Written by physicsgg

March 13, 2012 at 1:15 pm


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Galaxies Are Running out of Gas: Why the Lights Are Going out in the Universe

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A CSIRO study has shown why the lights are going out in the Universe. The Universe forms fewer stars than it used to, and a CSIRO study has now shown why: the galaxies are running out of gas.

A star-forming region in a nearby galaxy, imaged by the Hubble Space Telescope

Dr Robert Braun (CSIRO Astronomy and Space Science) and his colleagues used CSIRO’s Mopra radio telescope near Coonabarabran, NSW, to study far-off galaxies and compare them with nearby ones.

Light (and radio waves) from the distant galaxies has taken time to travel to us, so we see the galaxies as they were between three and five billion years ago.

Galaxies at this stage of the Universe’s life appear to contain considerably more molecular hydrogen gas than comparable galaxies in today’s Universe, the research team found.

Stars form from clouds of molecular hydrogen. The less molecular hydrogen there is, the fewer stars will form.

The research team’s paper is in press in Monthly Notices of the Royal Astronomical Society.

Astronomers have known for at least 15 years that the rate of star formation peaked when the Universe was only a few billion years old and has declined steeply ever since.

“Our result helps us understand why the lights are going out,” Dr Braun said.

“Star formation has used up most of the available molecular hydrogen gas.”

After stars form, they shed gas during various stages of their lives, or in dramatic events such as explosions (supernovae).

This returns some gas to space to contribute to further star formation.

“But most of the original gas — about 70% — remains locked up, having been turned into things such as white dwarfs, neutron stars and planets,” Dr Braun said….. Read the rest of this entry »

Written by physicsgg

August 22, 2011 at 7:46 pm

Researchers Develop Technique for Dynamically Controlling Plasmonic Airy Beams

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The movie shows the computer-based dynamical control of the trajectory and peak intensity position of plasmonic Airy beams achieved by Berkeley Lab’s Xiang Zhang.

One of the earliest lessons in science that students learn is that a ray or beam of light travels in a straight line. Students also learn that light rays fan out or diffract as they travel. Recently it was discovered that light rays can travel without diffraction in a curved arc in free space. These rays of light were dubbed “Airy beams,” after the English astronomer Sir George Biddell Airy, who studied what appears to be the parabolic trajectory of light in a rainbow.
Now, scientists with the Lawrence Berkeley National Laboratory (Berkeley Lab) have demonstrated the first technique that provides dynamic control in real-time of the curved trajectories of Airy beams over metallic surfaces. This development paves the way for fast-as-light, ultra-compact communication systems and optoelectronic devices,and could also stimulate revolutions in chemistry, biology and medicine.

The key to the success of this work was their ability to directly couple free-space Airy beams – using a standard tool of optics called a “grating coupler” – to quasi-particles called surface plasmon polaritons (SPPs). Directing a laser beam of light across the surface of a metal nanostructure generates electronic surface waves – called plasmons – that roll through the metal’s conduction electrons (those loosely attached to molecules and atoms). The resulting interaction between plasmons and photons creates SPPs. By directly coupling Airy beams to SPPs, the researchers are able to manipulate light at an extremely small scale beyond the diffraction limit…… Read the rest of this entry »

Written by physicsgg

August 12, 2011 at 7:42 am

Rotating cylinder puts a new spin on slow light

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Light that has shone through a rotating ruby cylinder is rotated either clockwise or anti-clockwise depending upon the rotation of the cylinder

Physicists in the UK and Canada claim to have demonstrated for the first time how a spinning medium can rotate a transmitted image. According to the researchers, the phenomenon could be used to encode images with extra data.
It has long been known that a moving medium can shift the position of passing light. The reason is that the light’s photons can be absorbed by the medium’s atoms, which jump into a higher energy state as a result. A moment later, these atoms return to their original state, re-emitting the photons. But by this time the atoms have moved slightly, so the photons continue their path from that new position…… Read the rest of this entry »

Written by physicsgg

July 6, 2011 at 8:47 am

Posted in Materials Science, QUANTUM PHYSICS

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