A precision measurement of the gravitational redshift by the interference of matter waves

One of the central predictions of metric theories of gravity, such as general relativity, is that a clock in a gravitational potential U will run more slowly by a factor of 1 + U/c², where c is the velocity of light, as compared to a similar clock outside the potential1.

This effect, known as gravitational redshift, is important to the operation of the global positioning system, timekeeping, and future experiments with ultra-precise, space-based clocks ( such as searches for variations in fundamental constants ).

The gravitational redshift has been measured using clocks on a tower, an aircraft and a rocket, currently reaching an accuracy of 7×10^-5.

Here we show that laboratory experiments based on quantum interference of atoms enable a much more precise measurement, yielding an accuracy of 7×10^-9.

Our result supports the view that gravity is a manifestation of space-time curvature, an underlying principle of general relativity that has come under scrutiny in connection with the search for a theory of quantum gravity.

Improving the redshift measurement is particularly important because this test has been the least accurate among the experiments that are required to support curved space-time theories.

Paul Krugman: Good and Boring ("Right now, Canada is a very important role model")

First, some background. Over the past decade the United States and Canada faced the same global environment. Both were confronted with the same flood of cheap goods and cheap money from Asia. Economists in both countries cheerfully declared that the era of severe recessions was over.
But when things fell apart, the consequences were very different here and there.

In the United States, mortgage defaults soared, some major financial institutions collapsed, and others survived only thanks to huge government bailouts. In Canada, none of that happened. What did the Canadians do differently ?

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NIST’s Second ‘Quantum Logic Clock’ Based on Aluminum Ion is Now World’s Most Precise Clock

Physicists at the National Institute of Standards and Technology (NIST) have built an enhanced version of an experimental atomic clock based on a single aluminum atom that is now the world’s most precise clock, more than twice as precise as the previous pacesetter based on a mercury atom. The new aluminum clock would neither gain nor lose one second in about 3.7 billion years, according to measurements to be reported in Physical Review Letters ( preprint ). The new clock is the second version of NIST’s  quantum logic clock , so called because it borrows the logical processing used for atoms storing data in experimental quantum computing, another major focus of the same NIST research group. ( The logic process is described at http://www.nist.gov/public_affairs/releases/logic_clock/logic_clock.html#background ) The second version of the logic clock offers more than twice the precision of the original.

The Quantum Physics of Photosynthesis

By hitting single molecules with quadrillionth-of-a-second laser pulses, scientists have revealed the quantum physics underlying photosynthesis, the process used by plants and bacteria to convert light into energy, at efficiencies unapproached by human engineers. The quantum wizardry appears to occur in each of a photosynthetic cell’s millions of antenna proteins. These route energy from electrons spinning in photon-sensitive molecules to nearby reaction-center proteins, which convert it to cell-driving charges Almost no energy is lost in between. That’s because it exists in multiple places at once, and always finds the shortest path.

Read More in
http://www.wired.com/wiredscience/2010/02/quantum-photosynthesis/#ixzz0eVrEvcho

Pablo Antillano: "Tomás Eloy Martínez cambió el Periodismo Venezolano"

En mi generación casi nadie discute que Tomás Eloy Martínez partió en dos la historia de nuestro periodismo. En la época que él llegó al país, los periodistas de El Nacional asumían como maestros a Moradell y a Mario Delfín Becerra, y se sentían herederos de Miguel Otero Silva y Federico Álvarez, de Sergio Antillano y Héctor Mujica, de Arístides Bastidas y Pascual Venegas Filardo, de Antonio Arráiz y Jesús Sanoja. Se hacía un periodismo correcto, devoto de la noticia, el tubazo, el objetivismo y la pirámide invertida. Aunque simpatizaban, en su mayoría, con causas de izquierda suscribían las normas clásicas del diarismo norteamericano.

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