Physics

The running joke in science has always been that the metric system was invented by the French to combat English predominance culturally - and they got the measurement wrong.

Still, it caught on ( though the French calendar didn't ) and that International System of Units (SI) is used on everything from beer cans to Olympic races. But some of it still isn't entirely accurate, as discussed in Making A More Accurate Kilogram ( along with that same poke at the French ) because man-made objects can change.

The English could have the last laugh. U.K.

For almost 75 years, astronomers have believed that the Universe has a large amount of unseen or ‘dark’ matter, thought to make up about five-sixths of the matter in the cosmos. With the conventional theory of gravitation, based on Newton’s ideas and refined by Einstein 92 years ago, dark matter helps to explain the motion of galaxies, and clusters of galaxies, on the largest scales.

Now two Canadian researchers at the Perimeter Institute for Theoretical Physics suggest that the motion of galaxies in a distant cluster is more easily explained by a Modified Gravity (MOG) theory than by the presence of dark matter.

Sandia National Laboratories’ Z machine, the world’s largest producer of X-rays, shook the ground for several hundred yards in every direction for the first time since July 2006, when the 22-year-old facility was gutted to undergo a complete refurbishment at a total project cost of $90 million.

Z has been overbooked in recent years with requests for experiment time from national labs, universities, and the international community. The facility is in demand because of Z’s capability to subject materials to immense pressures, compress spherical capsules to produce thermonuclear fusion reactions, fire objects much faster than a rifle bullet, and produce data for models of nuclear weapons effects — as well as, more arcanely, the conditions surrounding black holes in space.

The often counterintuitive world of quantum mechanics might appear to be the reserve of theoretical physicists pondering the possibility of parallel universes and cutting-edge experimentalists struggling to build unbreakable encryption devices or computers capable of factoring astronomical numbers in a heartbeat. But here is an experiment demonstrating effects of quantum mechanics that everybody can do at home.

Take a CD. Take an incandescent lightbulb (assuming those are still legal where you live), and look at its reflection in the silvery side of the CD.

A transistor containing quantum dots that can count individual photons (the smallest particles of light) has been designed and demonstrated at the National Institute of Standards and Technology (NIST).

The semiconductor device could be integrated easily into electronics and may be able to operate at higher temperatures than other single-photon detectors—practical advantages for applications such as quantum key distribution (QKD) for “unbreakable” encryption using single photons.

The NIST device, described in a new paper(1) can accurately count 1, 2 or 3 photons at least 83 percent of the time. It is the first transistor-based detector to count numbers of photons; most other types of single-photon detectors simply “click” in response to any small number of photons.

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2007 jointly to Albert Fert, Unité Mixte de Physique CNRS/THALES, Université Paris-Sud, Orsay, France, and Peter Grünberg, Forschungszentrum Jülich, Germany, "for the discovery of Giant Magnetoresistance".

Nanotechnology gives sensitive read-out heads for compact hard disks

This year's physics prize is awarded for the technology that is used to read data on hard disks. It is thanks to this technology that it has been possible to miniaturize hard disks so radically in recent years. Sensitive read-out heads are needed to be able to read data from the compact hard disks used in laptops and some music players, for instance.

Quantum dots have great promise as light-emitting materials, because the wavelength, or color, of light that the quantum dots give off can be very widely tuned simply by changing the size of the nanoparticles. If a single dot is observed under a microscope, it can be seen to randomly switch between bright and dark states. This flickering, or blinking, behavior has been widely studied, and it has been found that a single dot can blink off for times that can vary between microseconds and several minutes. The causes of the blinking, though, remain the subject of intense study.

In order to learn more about the origins of quantum dot blinking, researchers from the U.S.

We are all familiar with raindrops on our wind screens. The small ones stay in place while the big ones roll down the window. This is because surface tension holds the small drops onto the screen until they get to a size where the force of gravity is greater than the surface tension.

We are all familiar with raindrops on our wind screens. The small ones stay in place while the big ones roll down the window.

Einstein's Theory Of General Relativity has been under assault for the better part of a century. No one can really prove it wrong but it's commonly assumed to be wrong.

With atoms and molecules in a gas moving at thousands of kilometres per hour, physicists have long sought a way to slow them down to a few kilometres per hour to trap them.

A group of physicists from The University of Texas at Austin have found a way to slow down, stop and explore a much wider range of atoms than ever before.

Inspired by the coilgun that was developed by the University’s Center for Electromechanics, the group has developed an "atomic coilgun" that slows and gradually stops atoms with a sequence of pulsed magnetic fields.