Archive for the ‘Physics’ Category

National Ignition Facility recreates the interior of heavy stars

August 7th, 2017

Enlarge (credit: Lawrence Livermore National Lab)

In a lot of ways, stars are our model for creating nuclear fusion here on Earth, with fusion power often promoted as “harnessing the power of the Sun.” For all that, however, we have some surprising gaps in our understanding of what’s going on inside stars. That’s partly because we must infer what’s going on there based on the elements and particles that reach the solar surface, and partly because finding ways to test our theoretical models of fusion reactions is so difficult.

So there’s a certain appealing symmetry about a paper that was released by Nature Physics today. In it, researchers describe using the National Ignition Facility, built to study fusion using a giant laser, as a model for the interior of heavy stars. The results show that, despite their limitations, our earlier efforts to understand stellar fusion were on the right track.

Cross checking the cross-section

On a simple level, most stars fuse hydrogen to form helium. But things are obviously more complex than that. Most of the hydrogen in our Sun is the lightest form, with just a single proton as its nucleus. The helium produced in stars has two protons and two neutrons. Obviously, making helium from only protons requires a series of nuclear reactions, each with distinct probabilities of occurring that depend in part on the conditions inside the star. Complicating matters further, there are some other possible reactions that don’t lead directly to helium but can still occur inside a star, producing things like heavier isotopes of hydrogen.

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After 43 years, gentle touch of a neutrino is finally observed

August 3rd, 2017

Enlarge / The neutron source at Oak Ridge National Lab. (credit: Oak Ridge National Lab)

Neutrinos are noted for being extremely reluctant to interact with other matter. While it’s possible to build hardware that will detect them, these detectors tend to be enormous in order to provide sufficient material for the neutrinos to interact with. Those interactions also take the form of energetic events that transform the identity of particles (for example, converting protons to neutrons).

Given the neutrino’s low mass and tendency not to interact, the idea of detecting one simply bumping into another particle seems almost ludicrous. But that’s what scientists from Oak Ridge National Lab are reporting today. They’ve seen brief flashes as atoms get nudged by a neutrino, which imparts a tiny bit of its tiny momentum to the atom’s nucleus.

Oak Ridge National Lab is home to some hardware called the Spallation Neutron Source. This accelerates a beam of protons and smashes them into a tank of mercury. This creates debris that includes lots of neutrons, which are used for a variety of scientific purposes. But the debris also includes some neutrinos that are otherwise lost in the spray of particles that comes flowing out of the collisions.

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Taking quark-gluon plasma for a spin may un-break a fundamental symmetry

August 2nd, 2017

Enlarge / The STAR detector, with a bunch of physicists thrown in for scale. (credit: Brookhaven National Lab)

Researchers at Brookhaven National Laboratory’s RHIC particle accelerator have determined that an exotic form of matter produced in their collisions is the most rapidly spinning material ever detected. The material is called a quark-gluon plasma, and it provides us an opportunity to study the state that all matter was in immediately after the Big Bang.

The fact that the quark-gluon plasma spins provides us with an opportunity to study some theoretical ideas about the behavior of the strong force, one of the fundamental forces of nature that’s responsible for holding together the matter that we see around us.

The force is strong in these collisions

Brookhaven’s Relativistic Heavy Ion Collider (RHIC) and CERN’s Large Hadron Collider are the only facilities that can reach energies high enough to produce a quark-gluon plasma. Quarks are the building blocks of the heavier components of atoms; both protons and neutrons consist of three quarks bundled together. Gluons are the particles that hold them together in that bundle. Their interactions are governed by the strong force, and the rules of those interactions are described by a theory called quantum chromodynamics (often simply called QCD).

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Posted in gluons, particle physics, Physics, quantum chromodynamics, quarks, science, symmetries | Comments (0)

Cartoons from XKCD creator will appear in high school science textbooks

March 23rd, 2016

(credit: Randall Munroe)

Randall Munroe, creator of popular webcomic XKCD, recently published a new book called Thing Explainer: Complicated Stuff in Simple Words, in which he uses only the thousand most common words in the English language to explain how a variety of things work, from locks to nuclear bombs. Monroe’s publisher, Houghton Mifflin Harcourt, also publishes textbooks, and when editors in the textbook division saw proofs of Monroe’s Thing Explainer, they realized that his simple explanations could be used to augment high school textbooks.

You know, the old strategy employed ineffectively by dad joke-tellers everywhere: get the #teens on your side with humor.

(credit: Randall Munroe)

Luckily, Munroe’s Thing Explainer comics are absurd enough in their hyper-simplicity that they have a shot at breaking down the walls of sarcasm and ennui encircling the most eye-rolling of high school students.

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Posted in Biology, chemistry, Physics, textbooks, The Multiverse, thing explainer, xkcd | Comments (0)