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Category: physics

In 1999, the Egyptian chemist Ahmed Zewail received the Nobel Prize for measuring the speed at which molecules change their shape. He founded femtochemistry using ultrashort laser flashes: the formation and breakup of chemical bonds occurs in the realm of femtoseconds.

Now, atomic physicists at Goethe University in Professor Reinhard Dörner’s team have for the first time studied a process that is shorter than femtoseconds by magnitudes. They measured how long it takes for a photon to cross a hydrogen molecule: about 247 zeptoseconds for the average bond length of the molecule. This is the shortest timespan that has been successfully measured to date.

The scientists carried out the time measurement on a hydrogen molecule (H2) which they irradiated with X-rays from the X-ray laser source PETRA III at the Hamburg accelerator facility DESY. The researchers set the energy of the X-rays so that one photon was sufficient to eject both out of the hydrogen molecule.

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A major new milestone has just been achieved in the quest for superconductivity. For the first time, physicists have achieved the resistance-free flow of an electrical current at room temperature — a positively balmy 15 degrees Celsius (59 degrees Fahrenheit).

This has smashed the previous record of −23 degrees Celsius (−9.4 degrees Fahrenheit), and has brought the prospect of functional superconductivity a huge step forward.

“Because of the limits of low temperature, materials with such extraordinary properties have not quite transformed the world in the way that many might have imagined,” physicist Ranga Dias of the University of Rochester said in a press statement.

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The comparison of distant atomic clocks is foundational to international timekeeping, global positioning and tests of fundamental physics. Optica l-fibre links allow the most precise optical clocks to be compared, without degradation, over intracontinental distances up to thousands of kilometres, but intercontinental comparisons remain limited by the performance of satellite transfer techniques. Here we show that very long baseline interferometry (VLBI), although originally developed for radio astronomy and geodesy, can overcome this limit and compare remote clocks through the observation of extragalactic radio sources. We developed dedicated transportable VLBI stations that use broadband detection and demonstrate the comparison of two optical clocks located in Italy and Japan separated by 9,000 km. This system demonstrates performance beyond satellite techniques and can pave the way for future long-term stable international clock comparisons.

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Congratulations from Ogba Educational Clinic.

The 2020 Nobel Prize for Physics has been awarded to Roger Penrose, Reinhard Genzel and Andrea Ghez for their work on black holes.

The prize is worth 10 million Swedish krona (about $1.1 million) and half goes to Penrose, with Genzel and Ghez sharing the other half of the prize.

The Nobel Committee cites Penrose “for the discovery that black hole formation is a robust prediction of the general theory of relativity”, and Genzel and Ghez “for the discovery of a supermassive compact object at the centre of our galaxy”.

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Compressing simple molecular solids with hydrogen at extremely high pressures, University of Rochester engineers and physicists have, for the first time, created material that is superconducting at room temperature.

Featured as the cover story in the journal Nature, the work was conducted by the lab of Ranga Dias, an assistant professor of physics and mechanical engineering.

Dias says developing materials that are superconducting—without electrical resistance and expulsion of magnetic field at room temperature—is the “holy grail” of condensed matter physics. Sought for more than a century, such materials “can definitely change the world as we know it,” Dias says.

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Einstein’s theory of special relativity gave us the speed limit of the Universe — that of light in a vacuum. But the absolute top speed of sound, through any medium, has been somewhat trickier to constrain.

It’s impossible to measure the speed of sound in every single material in existence, but scientists have now managed to pin down an upper limit based on fundamental constants, the universal parameters by which we understand the physics of the Universe.

That speed limit, according to the new calculations, is 36 kilometres per second (22 miles per second). That’s about twice the speed of sound travelling through diamond.

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Could this be the energy source of the future?

The secret to the SPARC reactor is that its magnets will be built from new high-temperature superconductors that require much less cooling and can produce far more powerful magnetic fields. That means the reactor can be ten times more compact than ITER while achieving similar performance.

As with any cutting-edge technology, converting principles into practice is no simple matter. But the analysis detailed in the papers suggests that the reactor will achieve its goal of producing more energy than it sucks up. So far, all fusion experiments have required more energy to heat the plasma and sustain it than has been generated by the reaction itself.

The SPARC reactor is designed to achieve a Q factor of at least two, which means it will produce twice as much energy as it uses, but the analysis suggests that figure might actually rise to ten or more. The papers used the same physics and simulations as the ITER design team and other previous fusion experiments.

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