Page 1914 – Physics World

Home » Page 1914

Newton tops PhysicsWeb poll

Almost 400 people took part in the PhysicsWeb poll, each one naming their top-five physicists. The votes for each physicist were added up and weighted according to how they were ranked by individual voters. This meant that Newton received a higher score than Einstein even though more people voted for the twentieth century physicist. In contrast, a Physics World poll of the world’s leading physicists, in which individuals were not asked to rank their choices, put Einstein in the number one spot.

One surprise in both surveys was the large number of theorists in the top ten. And in the PhysicsWeb poll a lot of people voted for Stephen Hawking (who came 16th), while very few voted for nuclear physicist Hans Bethe. In contrast, the Physics World respondents gave Bethe the highest number of votes for a living physicist.

The list below contains all the physicists who scored more than 10 points in the PhysicsWeb survey (where a voter’s first choice received five points, their second choice four points, and so on).

PhysicsWeb survey	1	Albert Einstein
Albert Einstein	3	James Clerk Maxwell
Galileo Galilei	5	Werner Heisenberg
Niels Bohr	7	Richard Feynman
Richard Feynman	9
Erwin Schrödinger	>10

Clouds puzzles astronomers

Astronomers have argued about high-velocity clouds for over thirty-five years. Wakker and colleagues detected ionized sulphur in one such cloud using the Hubble Space Telescope. According to their calculations, the abundance of heavy elements in the cloud is only 9% of that found in the Sun. This, says Wakker, strongly suggests that the clouds replenish galaxies with hydrogen.

The discovery of molecular hydrogen by Richter’s team disputes this argument. Molecular hydrogen is usually created on dust grains composed of heavy elements such as iron. However, these grains could be debris from the nearby Magellanic Clouds – a set of ‘mini’ galaxies orbiting the Milky Way. This implies that the clouds studied by Richter’s team are not typical of high-velocity clouds in general.

The only answer is to make more measurements from other clouds says Robert Braun of the Netherlands Foundation for Research in Astronomy.

Physicists look to neutrino factory

When charged particles move in a circle they lose energy through synchrotron radiation. However, muons lose much less energy that electrons or positrons because they are 200 times heavier. This reduces the power needed to maintain the beam against energy loss.

The muons would be created from the decay of the pions produced when a megawatt proton beam strikes a metal target. According to the team’s current design, the muons would then be trapped by a magnetic field and channelled into a storage ring. The neutrinos would be produced when the muons decay. The well-defined beam produced by the neutrino factory could be used in a variety of experiments to probe beyond the standard model of particle physics.

Too many journals in China

The number of papers published by Chinese scientists in journals monitored by the US-based Institute for Scientific Information has grown from 3475 in 1983 to 10 033 in 1997. However, the proportion published in Chinese journals has dropped from 43.2% to 17% over the same period. The reason, say Ren and colleagues, is that Chinese journals have low prestige and that publishing in journals outside China has financial benefits for Chinese researchers. For example, Chinese scientists must publish papers in journals with impact factors of 2 or higher if they want to be promoted or have their grants renewed. However, no Chinese journal has an impact factor of higher than 0.5. Researchers also receive a 200 000 yen ‘bonus’ when they publish a paper in Science or Nature.

As well as cutting the number of journals from almost 4300 to under 3000, Ren and colleagues suggest that China should become more involved with online eprint servers. “This would efficiently enlarge the visibility of Chinese scientific reports and journals in the international scientific community,” they say.

New upper limit to neutrino mass

The team studied the radioactive decay of germanium 76, which cannot occur by normal beta decay in which one electron and one antineutrino would be emitted. The nucleus can, however, undergo double beta decay, which is extremely rare. This “neutrinoless” mode is only possible if the neutrino has mass and is its own antiparticle.

The experiment uses 11.5 kg of enriched germanium-76 in form of five high-purity Ge-detectors. The signature of neutrinoless double beta decay would be a peak in an energy spectrum at the Q-value of the reaction. Finding such a peak would be the first evidence that the neutrinos emitted in nuclear decays have mass. Neutrinos come in three types – electron neutrinos, muon neutrinos and tau neutrinos – which all could contribute to the double beta decay.

Last year, so-called neutrino oscillation experiments at the SuperKamiokande detector in Japan reported the first clear evidence for non-zero neutrino masses. However, such experiments can only measure mass differences between different neutrino mass eigenstates, while double beta decay could help to fix the absolute mass scale.

Brookhaven neutron source to close

The HFBR had become trapped in a economic and political battle between the Department of Energy and the US congress, with the latter refusing to release funds to restart the reactor. Moreover, it was costing $23 m per year to keep the reactor in standby mode. The high cost of restarting the reactor, and the cost of paying for upgrades to other neutron sources in the US, led to the decision to permanently close the reactor. “While I don’t believe the Brookhaven reactor is a threat to the public or the environment, we need to focus our limited resources on productive research,” said Bill Richardson, head of the DOE.

Mountain waves seen from space

Eckermann and Preusse analysed data from the cryogenic infrared spectrometer and telescope for the atmosphere (CRISTA), which was flown on the Space Shuttle Atlantis in 1994. They discovered that the gravity waves caused by the flow of air over mountains can exist as high as 45 km, which is well into stratosphere (Science 286 1534). The CRISTA instrument mapped the waves by measuring temperature fluctuations in the stratosphere. The results revealed gravity waves connected to the Andes, the Alps and central Eurasia – some of the largest mountain chains in the world.

“It is exciting that they have found experimental evidence of what we have only previously predicted,” said James Denholm-Price, a climate modeller from Kingston University in the UK. The research also has implications for global climate models and weather forecasting.

Eclipse confirms extrasolar planet

According to calculations by Marcy and colleagues, the planet has 63 percent of the mass of Jupiter and orbits the star every 3.5 days. On Thursday, the next time the star is eclipsed, more telescopes will be turned towards the star to confirm the findings. By combining data from both sets of observations, planet was found to have a diameter some 60 percent larger than that of Jupiter.

The results suggest that the density of the planet is about one-fifth that of liquid water, which would make it a gas giant. However, the planet is just over five million kilometres away from the star, which is only one-tenth the distance between Mercury and the Sun. As giant planets do not form close to stars, the data suggest that the planet drifted in from the outer edges of its star system.

Hubble Space Telescope shuts down

This is only the third time Hubble has been shut down since its launch in 1990. Three weeks of scientific data will be lost. During the repair mission, astronauts will replace all six gyroscopes, a fine guidance sensor, a transmitter, a spare solid-state recorder and a device that prevents batteries overheating. The crew will also install an advanced computer. A further servicing mission is planned for 2001.

E-beams tackle E. coli

For over a century milk has been pasteurised by heating it to 65 degrees Celsius for 30 minutes and then rapidly cooling it to below 10 degrees Celsius for storage. The new technique relies on energetic electrons from a linear accelerator. When the electron beam hits the E. coli, it deactivates the microbe’s DNA. “The whole process takes only a few seconds,” said Nan Unklesbay from the University of Missouri. “E. coli is one of the nastiest bacteria we know about and it can survive temperatures and acidic conditions that others cannot. We know that if we can kill E. coli, we can kill everything else too.”

The pasteurisation process also retains the colour, texture and flavour of the meat, unlike other preservative measures. So far the need to ensure an even distribution of the electrons means that the process is limited to liquids and products of a uniform consistency and shape.

Browse articles by content type