Lifeboat Foundation

Sawtooth swings—up-and-down ripples found in everything from stock prices on Wall Street to ocean waves—occur periodically in the temperature and density of the plasma that fuels fusion reactions in doughnut-shaped facilities called tokamaks. These swings can sometimes combine with other instabilities in the plasma to produce a perfect storm that halts the reactions. However, some plasmas are free of sawtooth gyrations thanks to a mechanism that has long puzzled physicists.

Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have recently produced complex simulations of the process that may show the physics behind this mechanism, which is called “magnetic flux pumping.” Unraveling the process could advance the development of fusion energy.

Physics

You’re probably sitting still, right? Wrong, absolutely wrong. Not only are you on a spinning orb, but you’re also traveling around 70,000 miles per hour around a star, in a galaxy that, observations imply, is sailing through space at over a million miles per hour.

If the above numbers seem shocking, they shouldn’t be. The laws of physics look and feel the same for any object so long as it’s not accelerating, the way you can’t feel that a car is traveling at a steady 60 miles per hour unless you look out the window. But that also makes our galactic speed hard to measure from here on Earth. The million-plus mile per hour number is based on measurements of how the most distant objects in the Universe appear to move in comparison to us, but scientists want to try to measure our acceleration by looking at more nearby objects.

How large is a neutron star? Previous estimates varied from eight to 16 kilometres. Astrophysicists at the Goethe University Frankfurt and the FIAS have now succeeded in determining the size of neutron stars to within 1.5 kilometres by using an elaborate statistical approach supported by data from the measurement of gravitational waves. The researchers’ report appears in the current issue of Physical Review Letters.

Neutron stars are the densest objects in the universe, with a mass larger than that of our sun compacted into a relatively small sphere whose diameter is comparable to that of the city of Frankfurt. This is actually just a rough estimate, however. For more than 40 years, the determination of the size of neutron stars has been a holy grail in nuclear physics whose solution would provide important information on the fundamental behaviour of matter at nuclear densities.

The data from the detection of gravitational waves from merging neutron stars (GW170817) make an important contribution toward solving this puzzle. At the end of 2017, Professor Luciano Rezzolla, Institute for Theoretical Physics at the Goethe University Frankfurt and FIAS, together with his students Elias Most and Lukas Weih already exploited this data to answer a long-standing question about the maximum mass that neutron stars can support before collapsing to a black hole—a result that was also confirmed by various other groups around the world. Following this first important result, the same team, with the help of Professor Juergen Schaffner-Bielich, has worked to set tighter constraints on the size of neutron stars.

Continue reading “Physicists set limits on size of neutron stars” »

In a breakthrough discovery, University of Wollongong (UOW) researchers have created a “heartbeat” effect in liquid metal, causing the metal to pulse rhythmically in a manner similar to a beating heart.

Their findings are published in the 11 July issue of Physical Review Letters, the world’s premier journal for fundamental physics research.

The researchers produced the heartbeat by electrochemically stimulating a drop of liquid gallium, causing it to oscillate in a regular and predictable manner. Gallium (Ga) is a soft silvery metal with a low melting point, becoming liquid at temperatures greater than 29.7C.

Some go to great lengths to understand the world around us – here are three extraordinary experiments from the history of science.

Small fluctuations in the universe could explain the origins of man.

Robbert Dijkgraaf explains how competing physics theories might explain why life exists.

Renewable resources are great, but they bring a new element of uncertainty to a power grid. This element can lead to failure in surprising ways, according to a new paper.

A team of researchers built a model of power grids that transport electricity from solar and wind power. That means that there are places where the grid receives fluctuating inputs of power, since levels of sunlight and wind and vary.

It would be silly to think we completely understand our universe, given how small the Earth is compared to the vastness of the cosmos. But from here on our tiny planet, it appears that much of the universe is missing. And I’m not just talking about dark matter. Regular stuff seems to be missing, too.

Astronomy fans probably know that as far as humans can tell, the universe is composed mostly of some mysterious, unexplained energy called dark energy that pushes it apart. The remaining piece, about a quarter, is dark matter, another unexplained thing that seems to build the universe’s skeleton. Just 4 percent is the regular matter that we can see: stars, planets, and interstellar and intergalactic gas. But the observed amount of this regular matter still falls perhaps a third short of the amount of stuff that physicists think should exist based on their models of the universe.