Quantum Method Closes in on Gravitational Constant - Scientific American

Quantum Method Closes in on Gravitational Constant - Scientific American; Researchers have been unable to identify the source of errors causing the disagreement in the conventional measurements. The set-up of the latest measurement is unlikely to contain the same errors as the torque method...

In the experiment described by Tino’s team, pulses of laser light tickle a cloud of rubidium atoms cooled to nearly absolute zero, driving the atoms to rise and fall like a fountain under the influence of gravity. The pulses split the 'matter wave' associated with each atom into a superposition of two energy states, each of which has a different velocity and reaches a different height — 60 or 90 centimeters — before falling back. The matter wave that rises farthest has a greater separation from the tungsten cylinders, and thus senses a slightly different gravitational pull. The difference in force imparts a measurable shift in the final state of the two matter waves when they recombine, creating an interference pattern.

New Measurement of Gravitational Constant Comes Up Higher Than Expected - Wired Science

New Measurement of Gravitational Constant Comes Up Higher Than Expected - Wired Science: The team, led by Terry Quinn, the former director of the International Bureau of Weights and Measures in France, used an updated version of Cavendish’s setup for one experiment. But they conducted an additional experiment, using a servo to counteract the twisting of the wire and figuring out the gravitational constant based on the voltage required to keep their apparatus from moving. Taken together, their tests yielded a new G value of 6.67545 × 10−11 m3⁄kg s2, which is higher than the current accepted value by about 240 parts per million.

Most accurate measurement of Boltzmann constant yet

Most accurate measurement of Boltzmann constant yet: In this study, the researchers... used acoustic thermometry to make the measurement by building an acoustic resonator and making amazingly precise measurements of the speed of sound in argon gas.
The researchers first cooled the resonator to the temperature of the triple point of water so they knew the temperature exactly in the current definition and filled it with argon gas...
Then they used the speed of sound measurement to calculate the average speed of the argon molecules and hence the average amount of kinetic energy that they had – from this they were able to calculate the Boltzmann constant with an extremely high accuracy.

Precise atomic clock may redefine time : Nature News & Comment

Precise atomic clock may redefine time : Nature News: First, like trapped-ion clocks, they measure the frequency of visible light, with a frequency tens of thousands of times higher than that of microwaves. Second, they measure the average emission frequency from several thousand trapped atoms rather than just one, and so the measurement statistics are better. The atoms are trapped in an optical lattice, rather like an electromagnetic egg box for holding atoms.

If OLCs are to succeed, however, researchers must show that one such clock ticks at exactly the same rate as another prepared in an identical way. This is what Lodewyck and colleagues have shown. They prepared optical lattices that each held about 10,000 atoms of the isotope strontium-87, and have shown that the two clocks stay in synchrony to within a precision of at least 1.5 × 10−16, which is as accurately as the experiment could measure.

Scientists examine nothing, find something - CSMonitor.com

Scientists examine nothing, find something - CSMonitor.com: They suggest that the impedance of a vacuum – another electromagnetic 'constant' whose value depends on the speed of light – itself depends only on the electric charge of the particles in the vacuum, and not their masses.

If their hypothesis is correct, it answers our question of where the speed of light comes from: It emerges from the total number of charged particles in the universe.

[1203.0102] GPS test of the local position invariance of Planck's constant

[1203.0102] GPS test of the local position invariance of Planck's constant: Publicly available clock correction data from the Global Positioning System was analyzed and used in combination with the results of terrestrial clock comparison experiments to confirm the local position invariance (LPI) of Planck's constant within the context of general relativity. The results indicate that h is invariant within a limit of |beta_h|<0.007, where beta_h is a dimensionless parameter that represents the extent of LPI violation.

Fundamental Constant May Depend on Where in the Universe You Are - ScienceNOW

Fundamental Constant May Depend on Where in the Universe You Are - ScienceNOW: Light from the quasars must pass through clouds of gas on its several-billion-year journey to Earth, and the atoms in the gas absorb light of specific wavelengths. So the spectrum of the light reaching Earth is missing these wavelengths and looks a bit like a bar code. The overall shift of the lines tells researchers how far away a gas cloud is and, hence, how long ago the light passed through it. The relative spacing of the lines lets them estimate the fine-structure constant at that time. Analyzing such data, Webb and colleagues argued that the fine-structure constant was about 1 part in 100,000 smaller 12 billion years ago than it is today...
Now Webb and his colleagues have scoured the southern sky themselves using the VLT. Their 153 clouds suggested a difference of 1 part in 100,000 in the fine-structure constant 12 billion years ago. Except in the southern sky, the constant seems to be larger. Connecting the two extremes with a line, the team found that absorption patterns in the clouds along that line are consistent with the fine-structure constant changing slowly through space—smaller in the distant northern sky and larger on the southern side.

NIST Posts Adjusted Values of the Physical Constants, Tweaking Gravity to Make Science More Precise | Popular Science

NIST Posts Adjusted Values of the Physical Constants, Tweaking Gravity to Make Science More Precise | Popular Science: The real news here isn’t really that we’ve discovered anything new but that science on the whole has reduced uncertainty, and that in turn impacts all physical science going forward. For instance, uncertainty in the constant alpha (that’s the fine-structure constant or the electromagnetic constant) has been reduced by 0.3 parts per billion, or cut in half based on the last evaluation of the constants in 2006.
Going forward, this adjustment to alpha will make a difference in (and--if the adjustment is correct--reduce the uncertainty of) all kinds of physics. The same is true for various other constants (there’s a nice overview of the heavy hitters here) like the radius of a proton or the Rydberg constant (relating to the atomic spectra in spectroscopy and thus far the most accurately measured fundamental constant--we think), whose values are still not completely “certain” but have been sharpened to introduce less and less uncertainty over the years.

Evidence Emerges That Laws of Physics Are Not Fine-Tuned For Life - Technology Review

Evidence Emerges That Laws of Physics Are Not Fine-Tuned For Life - Technology Review: "So what value of the cosmological constant best encourages galaxy and star formation, and therefore the evolution of life? Page says that a slightly negative value of the constant would maximise this process. And since life is some small fraction of the amount of matter in galaxies, then this is the value that an omnipotent being would choose.
In fact, he says that any positive value of the constant would tend to decrease the fraction of matter that forms into galaxies, reducing the amount available for life.
Therefore the measured value of the cosmological constant, which is positive, is evidence against the idea that the constants have been fine-tuned for life."

Variations in fine-structure constant suggest laws of physics not the same everywhere

Variations in fine-structure constant suggest laws of physics not the same everywhere: By measuring the quasar spectra, the researchers could gather data on the frequency of the electromagnetic radiation emitted by quasars at high redshifts, corresponding to a time about 10 billion years ago. During the time the light traveled through space to reach the telescopes, some of it was absorbed at specific wavelengths by very old gas clouds that today can reveal the chemical composition of the clouds...

The cloud compositions could help the scientists determine the fine-structure constant in those areas of the universe at that time, since alpha is a measure of the strength of the electromagnetic force between electrically charged particles...

By combining the data from the two telescopes that look in opposite directions, the researchers found that, 10 billion years ago, alpha seems to have been larger by about one part in 100,000 in the southern direction and smaller by one part in 100,000 in the northern direction...

The results also violate the Einstein Equivalence Principle, and suggest that the universe may be much larger than currently thought - or even infinite in size.

Radioactive decay rates vary with the sun's rotation: research

Radioactive decay rates vary with the sun's rotation: "The fluctuations we're seeing are fractions of a percent and are not likely to radically alter any major anthropological findings," Fischbach said. "One of our next steps is to look into the isotopes used medically to see if there are any variations that would lead to overdosing or underdosing in radiation treatments, but there is no cause for alarm at this point. What is key here is that what was thought to be a constant actually varies and we've discovered a periodic oscillation where there shouldn't be one."

Jenkins and Fischbach suggest that the changes in the decay rates are due to interactions with solar neutrinos, nearly weightless particles created by nuclear reactions within the sun's core that travel almost at the speed of light.