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Number 401, November 9, 1998 by Phillip F. Schewe and Ben Stein
INFLUENCE OF COSMIC RAYS ON EARTH'S CLIMATE. Do small changes in solar activity translate into climate change on our planet? One possible linkage is the sun's influence over the local flux of galactic cosmic rays (GCR); as the solar magnetic field gets stronger, fewer cosmic rays are able to penetrate to the inner solar system and Earth. And because the GCR are the biggest ionizer of air molecules in the lower atmosphere, they might play a role in processes like cloud formation. Henrik Svensmark, a physicist now at the Danish Research Institute (011-45-3-536-2475, hsv@dsri.dk), has studied the connection between GCR flux, solar activity, and climate on Earth. He finds that during the past 11-year solar cycle, Earth's cloud cover was more closely correlated with the GCR flux than with other solar activity parameters, such as solar radiance, the main energy emitted by the sun. Svensmark concludes that climate seems to be influenced by solar activity via the GCR-cloud connection. In other words, climate is partly affected by processes in deep space. (H. Svensmark, Physical Review Letters, 30 November 1998; see figure at Physics News Graphics.)
SUREFIRE QUANTUM ENTANGLEMENT, the ability to interlink two quantum particles with practically 100% certainty, has been achieved by a NIST group (Quentin Turchette, 303- 497-3328), advancing hopes for ultrapowerful quantum computers. Previously, physicists obtained entangled particles as a byproduct of some random or probabilistic process, such as the production of two correlated photons that occasionally occurs when a single photon passes through a special crystal. Receiving entangled pairs in this way is fine for tests of quantum nonlocality (Update 399), but entangling a large number of quantum particles--essential for building a practical quantum computer--becomes much less likely if it is dependent on a probabilistic process. In their "deterministic entanglement" process, the NIST researchers trap a pair of beryllium ions in a magnetic field. Using a predetermined sequence of laser pulses, they entangle one ion's internal spin to its external motion, and then entangle the motion to the spin of the other atom. The group believes that it will be able to entangle multiple ions with this process. (Turchette et al., Physical Review Letters, 26 October 1998.)
THE PETAWATT is the name for what is currently the world's most powerful laser, located at Lawrence Livermore National Laboratory. It can produce pulses of 1.3 quadrillion (peta) watts for half a trillionth of a second, more than 1300 times the entire electrical generating capacity of the US, if only for a short time. At the upcoming American Physical Society Division of Plasma Physics meeting, Steve Hatchett of Livermore (925-422-5916) will describe how the laser can produce highly improved, sub-millimeter resolution images of objects through almost 6 inches of lead (papers B1S.06 and B1I2.03). Shining the laser on a gold target, Tom Cowan (925-422-9678) of Livermore and his colleagues have ejected electrons with as much as 100 MeV energy, a new record for electrons coming from a solid (K6F.02). When these electrons were made to decelerate rapidly and release high-energy photons as a result, the researchers observed the photons to induce nuclear fission of uranium-238. Although such "photofission" has been seen before, the Petawatt may allow scientists to do newly detailed studies of nuclear processes. (Meeting program at www.aps.org/BAPSDPP98/) )
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