Posts Tagged ‘light’
FYI: Can Anything Move Faster Than Light?
Take Hydra, a cluster of galaxies about three billion light years away. Astronomers have measured the distance from the Earth to Hydra by looking at the light coming from the cluster. Through a prism, Hydra’s hydrogen looks like four strips of red, blue-green, blue-violet and violet. But during the time it takes Hydra’s light to reach us, the bands of color have shifted down toward the red end—the low-energy end—of the spectrum. On their journey across the universe, the wavelengths of light have stretched. The farther the light travels, the more stretched it gets. The farther the bands shift toward the red end, the farther the light has traveled. The size of the shift is called the redshift, and it helps scientists figure out the movement of stars in space. Hydra isn’t the only distant cluster of galaxies that displays a redshift, though. Everything is shifting, because the universe is expanding. It’s just easier to see Hydra’s redshift because the farther a galaxy is from our own, the faster it is moving away.
There is no limit to how fast the universe can expand, says physicist Charles Bennett of Johns Hopkins University. Einstein’s theory that nothing can travel faster than the speed of light in a vacuum still holds true, because space itself is stretching, and space is nothing. Galaxies aren’t moving through space and away from each other but with space—like raisins in a rising loaf of bread. Some galaxies are already so far away from us, and moving away so quickly, that their light will never reach Earth. “It’s like running a 5K race, but the track expands while you’re running,” Bennett says. “If it expands faster than you can run, you’ll never get where you’re going."
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In A Quantum First, Light Is Created From A Vacuum
According to quantum theory, empty space is, well, not that empty after all. Rather it is full of virtual particles – particles that quickly blip in and out of existence. Theory states that a mirror can absorb energy from some of these virtual photons, and re-emit it as actual photons. Of course, this only works if the mirror is traveling through the vacuum at nearly the speed of light, making it difficult to prove, to say the least.
Per Delsing and his team of physicists worked around this by using something called a superconducting quantum interference device, or SQUID. The SQUID, which is very sensitive to magnetic fields, acted as a mirror in the researchers’ superconducting circuit. They passed a magnetic field through the SQUID, switching the field’s direction a few billion times per second, which caused the SQUID to move back and forth at about 5 percent of the speed of light. Microwave photons were then observed. Consistent with the theory, the frequency of the released photons was about half the frequency of the mirror’s wiggling.
The researchers aren’t talking about their findings until their work has been peer-reviewed, but they will be presenting at a workshop next week in Italy.
[Nature]
Infrared Light Pulses Could Make Better Bionics for Deafness, Blindness and More
The team also used light to make heart cells contract. Their findings could someday be used to improve inner-ear implants for deafness and movement disorders; retinal implants that could use infrared pulses to stimulate the optic nerve; and even light-based pacemakers.
Infrared light can penetrate tissue, so optical implants would not have to touch the brain or connect directly to nerves, according to Richard Rabbitt, a bioengineering professor and senior author of the heart-cell and inner-ear-cell studies. “You will be able to implant optical devices and leave them there for life,” he said in a University of Utah news release.
In one study, Rabbitt and his colleagues used infrared light to make heart rat cells contract, and in another, they made toadfish inner-ear cells send signals to auditory nerve cells, which transmitted them to the brain. This worked because the infrared light affected the flow of calcium ions in and out of the cells’ power centers, which in turn affected how the heart cells contracted and how the ear cells released neurotransmitters, they found. In the heart cell study, an infrared pulse lasting one-5,000th of a second made the heart cells contract.
Optical pacemakers are unlikely to replace electrical ones anytime soon, Rabbitt acknowledges. But the ear studies could lead to better , he said.
Existing cochlear implants convert sound into electrical signals, which are transmitted to electrodes in the inner ear. Most have eight electrodes, but that means they only deliver eight frequencies of sound — and a healthy human can hear more than 3,000 frequencies, according to the University of Utah. But varied wavelengths of infrared light could correspond to various frequencies, potentially enabling inner-ear implants with hundreds or thousands of frequencies.
The research was published this month in The Journal of Physiology.
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Video: In Groundbreaking Demonstration of Flying Lightfoil, Laser Beam Generates Lift
Lift occurs when a push in one direction causes an object to move perpendicularly to that push. In the new lightfoil, light takes the place of the typical air or water to create that flow on a small scale. The team, led by Grover Swartzlander, fashioned micro-rods in the shape of an airplane wing (one side flat, one side rounded) and submerged them in water. Then they shot these lightfoils with 130 milliwatts of light, creating, for the first time optical lift. The rods moved up and to the side, as can be seen in the video below.
Compared with aerodynamic lift created by airfoils, this optical lift has an extremely steep angle – about 60 degrees. Light is refracted differently within the rod depending on its point of entry, and the bending of the beam causes lift.
While optical lift probably isn’t going to be used to fly 747s anytime soon, it could prove useful in powering micromachines or transporting nanoparticles. Swartzlander says he also believes that optical lift could be used to steer solar-sail-powered craft like IKAROS, which currently can only move straight in the direction the sun pushes it, and requires external forces, like jets of gas, to change direction.
Working Tractor Beam Can Move Objects 5 Feet With Just Light
Using only light, Australian researchers say they are able to almost five feet through the air. It’s more than 100 times the distance achieved by existing optical “tweezers,” the researchers say.
Not quite a simple grabby tractor beam, the new system works by shining a hollow laser beam at an object and taking advantage of air-temperature differences to move it around.
Moving objects with powerful light is not new — researchers have long been using optical tweezers to pluck bacteria-sized particles and move them a few millimeters. The U.S. Secretary of Energy, Steven Chu, won his Nobel Prize for work with optical tweezers. But Andrei Rhode and colleagues at the Australian National University say their new laser device can move glass objects hundreds of times bigger than bacteria, and shove them a meter and a half (5 feet) or more. Rhode says the 1.5-meter limit was only because of the size of the table where he placed his lasers — he thinks he can move objects up to 10 meters, or about 30 feet.
It works by shining a hollow laser beam around small glass particles, as Inside Science explains. The air around the particle heats up, but the hollow center of the beam stays cool. The heated air molecules keep the object balanced in the dark center. But a small amount of light sneaks into the hollow, warming the air on one side of the object and nudging it along the length of the laser beam. Researchers can change the speed and direction of the glass object by changing the lasers’ brightness.
The system needs heated air or gas to work, so in its present incarnation it wouldn’t work in space — sorry, Star Wars fans. But it could be used for a variety of purposes on Earth, like biological research or movement of hazardous materials.
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Nanoribbons Moved by Light: Could Propel Cell-Sized Submarines, Create Cloaking Devices, New Microchips
Originally, the researchers were investigating "superchiral" particles, which focus light into even smaller wavelengths than usual. However, the scientists realized that rather than just altering the light, the light also began to organize the superchiral nanoparticles. After a day of light exposure, the particles had formed into ribbons, and after three days the ribbons had woven themselves into nano-rope.
As soon as the researchers overcame their disbelief, they began exploring the applications of their discovery. One scientist is working on getting the nanoribbons to spin in the presence of light, essentially creating an artificial flagellum that could drive a nanosub. Another speculated that the light-warping effects of superchiral particles to create a cloaking device. And yet another wants to use the ribbons self-assembling power as a way to make microchips and other nanomachines.
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