This Week in Physics History: April 21 – 27

This Week in Physics History: April 21 – 27 April 27, 2008 • Apr. 23, 1858- German physicist & Nobel laureate Max Planck is born. Planck is credited as the father of quantum physics, because his solution to the ultraviolet catastrophe in blackbody radiation involved assuming that energy traveled in discrete packets, which he termed quanta. He derived a value, later called Planck's constant, which is crucial to performing quantum physics calculations. Out of this finding, Albert Einstein was able to explain the photoelectric effect and, subsequently, the field of quantum physics was born. He received the 1918 Nobel Prize in Physics for this work. • Apr. 25, 1900 - Austrian physicist Wolfgang Ernst Pauli is born. Pauli is best known for discovering the "Pauli Exclusion Principle" and extensive work in the concept of spin in particle physics and chemistry. He received the 1945 Nobel Prize in Physics for this work, having been nominated for it by Albert Einstein. • Apr. 22, 1904 - American physicist J. Robert Oppenheimer was born. Oppenheimer is sometimes called "the father of the atomic bomb" because he was the director of the Manhattan Project to develop the first nuclear bomb. • Apr. 25, 1953 - Francis Crick & James D. Watson publish their paper describing the double helix structure of DNA, which was determined largely with the use of x-ray crystallography. • Apr. 24, 1960 - German physicist & Nazi oppositionist Max von Laue died in Berlin. He was awarded the Nobel Prize in Physics in 1914 for his work in discovering the crystial diffraction of x-rays. • Apr. 21, 1994 - Astronomer Alexander Wolszczan announces the first discoveries of extrasolar planets (i.e. planets circling stars other than our Sun). • Apr. 26, 1994 - Physicists announce the first evidence of the top quark, a previously theoretical subatomic particle

Atomic Clock

Atomic Clock The mechanical clock served the needs of people for many centuries. Most people were satisfied with reckonings of time that gained or lost only a minute or two each day, and more accurate timepieces were available where greater precision was necessary, as with the operation of railroads or the determination of longitude at sea. In the course of the 20th century, however, the need for much greater accuracy arose. At the same time, recently discovered scientific principles made possible the building of clocks with almost unimaginable accuracy. In the 1920s, the rapidly expanding radio industry generated a need for the precise allocation of broadcast frequencies. Since frequency is by definition the number of cycles per second, the ability to broadcast on an exact frequency required an exact division of time. In the United States, the task of assigning radio frequencies was given to the National Bureau of Standards (NBS), an agency of the federal government's Department of Commerce. In response to the need for better time measurement, in the 1920s the NBS invented a clock based on a quartz crystal. When electrically stimulated, a quartz crystal vibrates at a fixed rate determined by its size and shape. This attribute allowed the construction of timepieces that were accurate to 1 second every 3 years. Quartz-crystal clocks were used to set radio frequency standards for 3 decades, but they suffered from a serious defect: Each clock ran at a slightly different rate. For most applications the differences were so small as to be irrelevant, but for others they were of crucial importance. Much more accurate clocks became possible in the late 1940s as a result of fundamental discoveries regarding the behavior of atoms. In particular, quantum physics had determined that atoms absorbed and emitted energy only at certain frequencies. In 1948, three physicists at the NBS—Harold Lyons, Benjamin Husten, and Emory Heberling—used this principle to build the first atomic clock. The clock used microwaves that were directed into ammonia gas. When the microwave frequency (about 24 billion hertz) was the same as the natural frequency of the hydrogen atoms in the ammonia, the atoms absorbed them. If the frequency was different, the microwaves hit a detector that triggered an electrical current. The current in turn adjusted the microwave frequency, which was then used to keep a crystal vibrating at a uniform rate. The clock was accurate to 1 second every 8 months. This was not as good as the best conventional quartz crystal clock, but there was ample room for further development. The next generation of atomic clocks was built around the element cesium. These clocks used vaporized cesium that had been magnetically divided so that one beam of atoms had identical energy states. When a microwave signal matched a cesium atom's natural frequency, it changed the atom's energy state. The atoms with a changed energy state were magnetically segregated and sent to a detector. As with the first atomic clock, the signal from the detector was used to stabilize the vibration frequency of a quartz crystal. In this way, it became possible to tell time that was accurate by 1 second every 300 hundred years. Development continued, and by 1970 the latest cesium clock operated with an accuracy of 1 second in 6,000 years. This made it more accurate than our natural timepiece, the Earth, which spins erratically due to axial wobbling caused by tides, the movement of the interior molten core, and even heavy snowfalls. Because atomic time slowly gets out of synch with Earth time, the Paris-based International Bureau of Time occasionally has to add or subtract a "leap second" to bring the two back together. Atomic clocks gain or lose only a few millionths of a second annually, yet the quest for even more accurate clocks continues. Increasingly accurate clocks are vital to a variety of scientific and technological ventures. Elementary-particle physicists are concerned with the detection of subatomic particles that may exist for a fraction of a nanosecond (a nanosecond is 10-9 seconds), while geologists study tiny movements of the Earth's tectonic plates in order to learn more about the cause of earthquakes. Television and radio broadcasting still require precise reckonings of time, especially as the airwaves get increasingly crowded and frequencies have to be kept within very narrow limits. Atomic clocks are also vital to the operation of sophisticated navigation technologies, where an error of a fraction of a second can throw an airplane several miles off course. References: 1.Margaret Coel, "Keeping Time by Atom," American Heritage of Invention and Technology, (1988)

Timeline: Physics[2007]

Timeline: Physics[2007] January 11: Scientists find three black holes in close proximity to each other.Astronomers spot a rare phenomenon: a trio of black holes. The black holes, called quasars, are about 10.5 billion light years from Earth and about 100 thousand light years from each other, about the width of our Milky Way Galaxy—a rare astronomical discovery. Each quasar emits more light than an average galaxy. Light now reaching Earth from the quasars is nearly as old as the universe; researchers hope to learn more about the chaotic nature and composition of the early universe by studying these quasars. February 2: Physicists discover way to measure extra dimensions, which provides evidence for string theory.A group of theoretical physicists have found that by looking at the universe moments after the big bang, they may find evidence to support string theory and the existence of extra dimensions. In addition to three dimensions of space and the fourth dimension of time, string theory proposes that there are six additional dimensions that make up the universe. It is thought that these six extra dimensions are hidden within the tiny strings that make up all matter and energy in the universe. The concept is difficult for most people to visualize, and until now, experimentally proving string theory was thought to be impossible. By comparing detailed measurements of cosmic background radiation—faint energy traces left over from the big bang—and comparing it to results predicted by string theory, researchers are hoping to discover the shape and nature of the six unseen dimensions within the tiny strings. February 14: Engineering professor resolves Einstein's twin paradox.Subhash Kak, an engineering professor from Louisiana State University, finds a solution to the twin paradox, a problem introduced in 1905 with the publication of Albert Einstein's theory of relativity. The paradox attempts to answer questions that arise when traveling at near the speed of light. The paradox is as follows: one twin leaves Earth on a spaceship traveling near the speed of light. The ship travels several light years away. When the ship returns to Earth, because of the phenomenon of time dilation—a consequence of relativity—the twin left behind on Earth is now older than his brother. The paradox is that, in this situation, it is the earthbound twin who is considered to be in motion relative to the spaceship and thus should be the one aging more slowly (which is not the case). Kak solved the paradox by measuring the motion of the Earth and the spaceship against a third, fixed point, rather than against each other. By employing high level mathematics, Kak also assumed that the spaceship travels through an anisotropic universe to come to his conclusion. The long-standing paradox here is resolved so that after the flight, there is no age difference between the twins. March 1: Scientists create coating made of nanoparticles that reflects virtually no light.Researchers have developed the world's most nonreflective material. The new coating has a refractive index, which controls how much light a material reflects, of 1.05, which is comparable to that of air. To achieve the low reflectivity state, the silica nanorods are placed on a coating of aluminum nitride at an angle of about 45°. Physicists are hoping to use the new antireflective coating to improve performance of light emitting diodes (LEDs), solar cells, and other optical hardware. 2007 April 2: NASA mission proves one of Einstein's relativity predictions.Astronomers determine that data collected from NASA's Gravity Probe B satellite proves that one of Albert Einstein's predictions about curved space is correct to within 1 percent. In his theory of relativity, Einstein predicted the geodesic effect, in which space is curved by the mass of an object. The effect is often illustrated by placing a heavy ball on a sheet of rubber. The depression that the ball makes in the sheet represents the distortion created by the Earth's mass on the space beneath it. Gravity Probe B is currently testing another of Einstein's predictions, called frame-dragging, in which a massive spinning object, such as the Earth, would drag the surrounding space and time with it as it rotates, just as the ball on the rubber sheet would drag the rubber if it were twisted. April 4: Scientists measure details of electrons tunneling out of atom.Researchers at the Max Planck Institute in Germany have performed experiments that measure the time it takes for an electron to "tunnel" out of an atom. Tunneling occurs when an electron escapes from the atom without additional energy, a feat that would be impossible if electrons obeyed the rules of classical physics. Electrons, however, follow the rules of quantum mechanics. The tunneling was measured to take less than 400 attoseconds, or 4 × 10−16 seconds. Scientists hope that the finding could be used to improve the X-ray laser, which would be instrumental in the early diagnosis of cancer. April 16: The highest frequency signal ever is produced.Engineers at UCLA produce the highest frequency electromagnetic signal ever produced: 324 gigahertz, or 324 billion cycles per second, 70 percent faster than previously attained. The device that created the record-breaking signal is a complementary metal oxide semiconductor (CMOS) device similar to the type used in computer processors. This range of frequencies, called "submillimeter" because the wavelength is just under one millimeter (0.04 inch), can be used to see through clouds and fog, and also in high-resolution sensors on spacecraft. Engineers also hope to use the higher frequency limit to increase available bandwidth of communication systems, which would lead to speedier and more efficient voice, data, and video transmissions. May 3: Mercury's core may be liquid.The results of a five-year study reveal Mercury has a liquid core of molten iron, rather than a solid core, as previously believed. By bouncing radio signals sent from a ground telescope in California off of the planet, then receiving them again at a facility in West Virginia, astronomers were able to measure small twists in Mercury's rotation that were twice as high as expected for a planet with a solid core. This supports data taken by Mariner 10 in 1974, which measured a weak magnetic field on Mercury's surface—a key indicator of a liquid core. May 15: Hubble Telescope detects ring of dark matter.NASA's Hubble Space Telescope has detected a ripple around two collided galaxies that adds compelling evidence for the existence of dark matter. Astronomers believe that dark matter makes up a majority of the matter in the universe. The ring is 2.6-million-light-years wide and bends the light around it to create a ripple effect, which researchers claim is dark matter's "calling card." The ring surrounds cluster ZwCl0024+1652, which comprises the remnants of two galaxies that collided over a billion years ago. May 21: Researchers find new production method for hydrogen fuel.A new type of fuel, in the form of aluminum and gallium pellets, may offer an efficient way to produce and store hydrogen, which many scientists hope is the clean fuel that will replace gasoline and oil. Until now, the major roadblock to producing hydrogen-powered cars has been the absence of an efficient method of producing hydrogen. In the new procedure, gallium is added to aluminum pellets causing the aluminum to react with water. This splits the hydrogen and oxygen in the water, releasing pure hydrogen. The pellets are easily stored and transported and researchers say the cost of the new fuel would be competitive with that of gasoline. June 12: Scientists demonstrate quantum communication with light.Scientists working at the European Space Agency (ESA) have shown that a strange property of light, called quantum entanglement, can be used for communications over long distances. In the study, a laser beam was transmitted across a distance of 89 miles (144 km) to a remote satellite. Quantum entanglement hinges on the fact that when light is emitted from one source, such as a laser, it retains information about all of the photons that it interacted with, so if two photons are separated after they interact, they can retain information about the other, even if they are miles apart. Quantum entanglement held steady even through Earth's atmosphere. Researchers also showed that making a measurement anywhere along the path of the signal will be noticed, so eavesdroppers would be detected. Therefore, these lines of communications would be perfect for sending and receiving confidential information. June 28: Nano-sized light source invented.Researchers at the University of California at Berkeley have invented a nano-sized light source able to emit light across the visible spectrum. This light source could have profound implications in the development of nanophotonic technology, bioimaging, and cybercryptography. July 12: New lens device will shrink huge light waves to pinpoints.University of Michigan scientists have constructed a new lens that can break light waves into much smaller points than is possible with a standard lens. This new technology could be used to increase data storage on media such as CDs, which are currently limited by the size of the electromagnetic wave (and thus the number of bits they can hold). September 12: Spin measured on individual atoms.Scientists at the University of California, Berkeley, succeed in measuring the spin of individual iron atoms place atop a film of copper atoms. While scientists have long known that the electrons of individual atoms have one of two spin qualities ("up" or "down"), until recently these have only been measured in a film of orderly arranged atoms. Researchers hope that someday atomic spin could be used as a digital switch in smaller, more efficient computers. September 12: New particle created by uniting matter and antimatter.A team of scientists from the University of California creates molecules of di-positronium, a particle predicted in 1946, by bonding electrons with positrons. The particles have remained elusive due to the scarcity of antimatter positrons in the universe. Scientists solved this problem by trapping and gradually accumulating 20 million positrons, before releasing them into a silica sponge. Before annihilating, many positrons bonded to electrons, forming di-positronium molecules. The molecules also annihilated within a quarter of a nanosecond (one billionth of a second). The team speculates that the new molecule could possibly be incorporated into the design of a powerful gamma ray laser. September 12: Russians test fuel-air bomb.The Russian air force tests a fuel-air bomb, claiming that it is larger than the American MOAB (Massive Ordinance Air Burst) bombs. If claims are correct, the fuel-air bomb is the largest non-nuclear bomb in the world. The fuel-air bomb operates in two stages. First, a primary charge disperses ignitable material into the surrounding atmosphere, which is then exploded by a larger, secondary charge. Russia has stated that the explosion has the force of 44 tons of TNT, sufficient to demolish a four-story building at the test site. September 24: An experiment aboard the European Space Agency's Foton satellite confirms liquid fluctuation.An experiment on board the European Space Agency's Foton satellite has confirmed scientific theories about fluid fluctuation. Fluctuations in temperature and concentration are an intrinsic property of liquids, but the changes are so small as to be difficult to observe using traditional methods. In microgravity's strong temperature gradient—great differences across a small distance—the satellite is able to photograph visible fluctuations and transmit the images to Earth, less than a week after launch. October 2: Scientists develop a two-dimensional, microscopic "invisibility cloak."A team of physicists from the United States have created a visible light "invisibility cloak" 10 micrometers in diameter. By injecting polarized cyan light onto a film of gold, the light is transformed into plasmons that redirect light around the gold, effectively making it invisible in two dimensions. Another American team created a three-dimensional microwave invisibility cloak in October 2006. In the visual light cloak, dimensionality was decreased to accommodate the much smaller wavelength. October 22: Microscopic nanoantenna laser developed.Engineers at Harvard have designed a laser capable of producing detailed images on a nanometric scale. The laser, called a quantum cascade laser nanoantenna, is comprised of two gold rods separated by a gap of one nanometer. By focusing light of a certain spectrum through the gap, the laser is able to scan across samples at a resolution much higher than that of the wavelength of the light itself. The new technology enables researchers to see, in great detail, the chemical composition of the interiors of cells and other nanoscopic materials. October 29: Magnetic separation technique developed.A new magnetic separation technique called magnetophoresis has been developed by a joint team of researchers at Duke University and Perdue University. The process involves using a magnetic field and microchip to separate and sort magnetic beads according to size. The beads could be attached to a substance, such as a suspected pathogen, and then separated from the sample by the magnet. The technique could have applications in medicine, as a method for testing for multiple pathogens at once. October 31: Scientists develop functioning nanoradio.A team of researchers from the University of California Berkeley and the Lawrence Berkeley National Laboratory has developed a working radio from a single fiber of carbon nanotube less than one micrometer long. The device is powered by a battery and functions by running a stream of electrons along the tube and across a vacuum to a negatively charged copper anode. Radio waves disrupt the flow of electrons, and the signal is relayed and broadcast through a speaker. The technology could have broad applications, since any system in which a nanoradio is embedded could potentially be controlled by radio. November 12: Scientists discover a new method for storing hydrogen.Scientists at the University of Virginia have found a new class of materials for storing hydrogen. The material doubles, from seven to fourteen percent, the storage capacity by weight for hydrogen. Earlier materials required extremely low temperatures for storage while the new material is functional at room temperature. The technology could have applications in energy storage and transportation. December 7: New oil-repelling technology allows for the creation of self-cleaning materials. Researchers from MIT and the U.S. government have designed a material that is repellent to oils. This new material is known as superoleophobic because oil bounces off, making it essentially self-cleaning. Oleophobic materials are much more complicated than water-repellant materials as oil tends to spread quickly and cling to surfaces. Possible applications are self-cleaning displays on cell-phones. December 7: Scientists gain new insight on solar wind. Information recorded by the NASA telescope Hinode provides a clearer picture as to the effect of magnetic waves called Alfvén waves, on solar winds. The understanding of solar winds is important, as they can disrupt power grids and satellite communications. December 13: Physicists discover "rogue" optical waves. Scientists, using waves of light to understand aquatic waves, have pinpointed the cause of rogue waves. Rogue waves are large oceanic waves that seem to happen irrespective of tides. The effect was reproduced in a lab by hitting a light wave with sound in what scientists are calling a "sweet spot." Further investigation will follow on the effects of sound on aquatic waves.

'Power shirt' generates watts as you walk

'Power shirt' generates watts as you walk Two sets of zinc oxide nanowires meet teeth-to-teeth, allowing the gold-coated microfibres to scrub those not coated with gold. This generates electricity by the so-called piezoelectric effect, the fundamental concept behind a 'power shirt' A microfibre fabric that generates enough of its own electricity to recharge a mobile phone or ensure that an mp3 player never runs out of power has been developed by US scientists. If made into a shirt, the fabric could harness power from its wearer simply walking around or even from a slight breeze, they report today in the journal Nature. "The fibre-based nanogenerator would be a simple and economical way to harvest energy from the physical movement," says Professor Zhong Lin Wang of the Georgia Institute of Technology, who led the study. The nanogenerator takes advantage of the semiconductive properties of zinc oxide nanowires, tiny wires 1000 times smaller than the width of a human hair, embedded in the fabric.The wires are formed into pairs of microscopic brush-like structures, shaped like a baby-bottle brush. One of the fibres in each pair is coated with gold and serves as an electrode. As the bristles brush together through a person's body movement, the wires convert the mechanical motion into electricity. "When a nanowire bends it has an electric effect," Wang says. "What the fabric does is it translates the mechanical movement of your body into electricity." Coating the fibres His team made the nanogenerator by first coating fibres with a polymer and then a layer of zinc oxide. They then dunked this into a warm bath of reactive solution for 12 hours. This encouraged the wires to multiply, coating the fibres. "They automatically grow on the surface of the fibre," Wang says. "In principle, you could use any fibre that is conductive." They then added another layer of polymer to prevent the zinc oxide from being scrubbed off. And they added an ultra-thin layer of gold to some fibres, which works as a conductor. Could it be static? To ensure all that friction was not just generating static electricity, the researchers conducted several tests. The fibres produced current only when both the gold and the zinc oxide bristles brushed together. So far, Wang says the researchers have demonstrated the principle and developed a small prototype. "Our estimates show we can have up to 80 milliwatts per square metre of this fabric. This is enough to power a little iPod or charge a [mobile] phone battery," he says. "What we've done is demonstrate the principle and the fundamental mechanism

Recent Physics News

Recent Physics News [2008] January 8: Scientists create the most light-absorbent material yet. Scientists have created a material that absorbs more than 99.9 percent of light. It is composed of tiny carbon tubes standing on end and is more than three times darker than the current record holder (a nickel-phosphorous alloy), and 30 times darker than the current benchmark, which is also made of carbon. Practical applications include usage on solar panels. January 9: Researchers use silicon nanowires to convert heat into electricity. U.S. scientists have discovered that by using rough, rather than smooth, nanowires they can more efficiently turn heat into electricity. Scientists hope to eventually be able to build on this technology to improve the efficiency of energy production. February 13: Scientists create a theoretical "periodic table" of black hole orbit patterns.The shape of the orbital pattern an object traces is largely influenced by its proximity to the black hole. The farthest objects trace standard elliptical paths, whereas the nearest objects trace more complex paths that could be essentially different each time. The table of patterns was compiled using computational models of idealized situations and will be used

Physicists create superinsulators

Physicists create superinsulators U.S. and European scientists have discovered a fundamental state of matter that they say opens new directions of inquiry in condensed matter physics. Researchers at the U.S. Department of Energy's Argonne National Laboratory, in collaboration with several European institutions, have created superinsulators that they say might result in a new generation of microelectronic devices. Led by Argonne senior scientist Valerii Vinokur and Russian scientist Tatyana Baturina, the researchers from Belgium, Germany, Russia and the United States fashioned a thin film of titanium nitride that they then chilled to near absolute zero. When they tried to pass a current through the material, the researchers noticed its resistance suddenly increased by a factor of 100,000 once the temperature dropped below a certain threshold. The same sudden change also occurred when the researchers decreased the external magnetic field. Like superconductors, which have applications in many different areas of physics, the scientists say superinsulators could eventually find their way into a number of products, including circuits, sensors and battery shields.

Optical Illusions & Visual Phenomena These pages demonstrate visual phenomena, and »optical« or »visual illusions«. The latter is more appropriate, because most effects have their basis in the visual pathway, not in the optics of the eye. http://www.michaelbach.de/ot/

Flash Animations for Physics Flash animations for illustrating Physics content. This page provides access to those animations which may be of general interest. The animations will appear in a separate window. http://www.upscale.utoronto.ca/GeneralInterest/Harrison/Flash

Making Sound: Voice Coil The voice coil is a basic electromagnet. An electromagnet is a coil of wire, usually wrapped around a piece of magnetic metal, such as iron. Running electrical current through the wire creates a magnetic field around the coil, magnetizing the metal it is wrapped around. The field acts just like the magnetic field around a permanent magnet: It has a polar orientation -- a "north" end and and a "south" end -- and it is attracted to iron objects. But unlike a permanent magnet, in an electromagnet you can alter the orientation of the poles. If you reverse the flow of the current, the north and south ends of the electromagnet switch. This is exactly what a stereo signal does -- it constantly reverses the flow of electricity. If you've ever hooked up a stereo system, then you know that there are two output wires for each speaker typically a black one and a red one. http://electronics.howstuffworks.com/speaker5.htm

SPEAKER-PHONE Got some old boom box, computer or stereo speakers? The RECYCLED SPEAKERS PHONE is an easy to make intercom. http://www.sciencetoymaker.org/SpeakPhone/index.html

The Floating Water Bridge

J. Phys. D: Appl. Phys. 40 P.6112-61149(2007)

Water undoubtedly is the most important chemical substance in the world.When two beakers (100 mL) set on an even plane, one was fixed,the other movable and controlled by a step motor, and both beakers were separated by 1 mm. The beakers were filled with triply deionized water such that the water surface was about 3mm below the beaker’s edge.Now one electrode was charged with 15 kV, the other was set to ground potential.Since the voltage generators provide a limited current output was stable at 0.5 mA. After a short electric discharge, which was build up between the two water surfaces,a water connection formed spontaneously between the two beakers; the water moved up the glass walls and built a water bridge.