“Volumes” is an experimental art film by Maxim Zhestkov using physics-based particle animation. Waves and unseen forces send billions of color-changing particles aloft in the film. The motions – especially the way the particles seem to tear themselves – are reminiscent of a complex fluid, like yogurt. These substances have both liquid-like (viscous) and solid-like (elastic) properties depending on the forces they experience. Zhestkov’s particles are similar; they move like a fluid but tear more like a solid.

Watch the video:
https://vimeo.com/257761811

#fluiddynamics #science #physics #granularmotion #complexfluids #nonNewtonianfluids #viscoelasticity

How Does Magnetic Putty Work?
Magnetic putty becomes magnetic when iron oxide particles are added to silly putty. The iron oxides magnetize the putty making it a million times more fun and entertaining than regular putty. When magnets are within range of the influence of its magnetic field, the putty will slowly swallow them. Because the magnetic field of the putty is strongest at the center of the blob, the magnets are engulfed. The putty slowly sucks magnets in until they reach the strongest point of the magnetic field.

Good to know:
https://nationalmaglab.org/education/magnet-academy/plan-a-lesson/magnetic-putty

Video:
https://www.youtube.com/watch?v=jIVplzQ3xIA

#physics #magneticputty #science #experiments

Neutrino experiment at Fermilab delivers an unprecedented measurement
Tiny particles known as neutrinos are an excellent tool to study the inner workings of atomic nuclei. Unlike electrons or protons, neutrinos have no electric charge, and they interact with an atom's core only via the weak nuclear force. This makes them a unique tool for probing the building blocks of matter. But the challenge is that neutrinos are hard to produce and detect, and it is very difficult to determine the energy that a neutrino has when it hits an atom.

This week, a group of scientists working on the MiniBooNE experiment at the Department of Energy's Fermilab reported a breakthrough: They were able to identify exactly-known-energy muon neutrinos hitting the atoms at the heart of their particle detector. The result eliminates a major source of uncertainty when testing theoretical models of neutrino interactions and neutrino oscillations.

"The issue of neutrino energy is so important," said Joshua Spitz, Norman M. Leff assistant professor at the University of Michigan and co-leader of the team that made the discovery, along with Joseph Grange at Argonne National Laboratory. "It is extraordinarily rare to know the energy of a neutrino and how much energy it transfers to the target atom. For neutrino-based studies of nuclei, this is the first time it has been achieved."

To learn more about nuclei, physicists shoot particles at atoms and measure how they collide and scatter. If the energy of a particle is sufficiently large, a nucleus hit by the particle can break apart and reveal information about the subatomic forces that bind the nucleus together.

But to get the most accurate measurements, scientists need to know the exact energy of the particle breaking up the atom. That, however, is almost never possible when doing experiments with neutrinos.

Like other muon neutrino experiments, MiniBooNE uses a beam that comprises muon neutrinos with a range of energies. Since neutrinos have no electric charge, scientists have no "filter" that allows them to select neutrinos with a specific energy.

MiniBooNE scientists, however, came up with a clever way to identify the energy of a subset of the muon neutrinos hitting their detector. They realized that their experiment receives some muon neutrinos that have the exact energy of 236 million electronvolts (MeV). These neutrinos stem from the decay of kaons at rest about 86 meters from the MiniBooNE detector emerging from the aluminum core of the particle absorber of the NuMI beamline, which was built for other experiments at Fermilab.

Energetic kaons decay into muon neutrinos with a range of energies. The trick is to identify muon neutrinos that emerge from the decay of kaons at rest. Conservation of energy and momentum then require that all muon neutrinos emerging from the kaon-at-rest decay have to have exactly the energy of 236 MeV.

Source & further reading: https://phys.org/news/2018-04-neutrino-fermilab-unprecedented.html#jCp

Journal article:
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.141802

#physics #neutrinos #Fermilab #science

Asteroseismology reveals the structure of a white dwarf
Using asteroseismology, scientists can analyze stars' intrinsic pulsations to tease out the physical properties of stellar interiors. Now scientists have applied asteroseismology to unmask a white dwarf—a star in the slow cooling phase that marks the end of the life cycle of all but the most massive stars. The results confirm the broad contours of stellar evolution theory but significantly challenge the particulars.

Article:
https://physicstoday.scitation.org/doi/10.1063/PT.3.3862

Photo:
A white dwarf undergoing a nova explosion, as observed by NASA’s Chandra X-Ray Observatory.

#physics #science #research #asteroseimology

A Tantalizing Signal From the Early Universe
The astronomy community is buzzing over radio telescope measurements that could indicate radiation from the universe's first stars, a mere 180 million years after the Big Bang. The signal, detected by radio antennae situated in the Australian desert, does not match theoretical predictions of what those early stellar signatures would look like.

That's both exciting and worrying: It could mean that hydrogen atoms in the early universe were interacting with cold, lightweight particles of dark matter. But it also could mean that the signal is the result of instrument calibration errors or other factors. Other radio observatories should be able to chime in over the next couple of years to confirm or refute the new results.

Source:
https://www.insidescience.org/news/astronomers-catch-faint-message-universe%E2%80%99s-first-stars

Journal article (under paywall):
https://www.nature.com/articles/nature25792

Image:
This handout photo released by Nature on February 28, 2018 shows a timeline of the universe, updated to show when the first stars emerged reflecting a recent discovery by researchers at Arizona State University that the first stars emerged by 180 million years after the Big Bang.

#physics #universe #BigBang #science #astronomy #research

Remembering Joe Polchinski the modest physicist who conceived a multiverse
Creativity and modesty are two of the qualities that made Joe Polchinski an extraordinary theoretical physicist. The early pioneer of string theory died this month at age 63.

Polchinski was an early pioneer of string theory, the mathematical apparatus picturing the basic particles of matter and force as supertiny wriggling strands of energy known as superstrings. His contributions to the field were immense. As a young professor at the University of Texas at Austin in the 1980s, he developed a branch of superstring theory involving objects called supermembranes.

Superstrings are one-dimensional objects (like lines, hence “strings”) vibrating like rubber bands in multidimensional space. (String math presupposed more dimensions than the usual three.) Polchinski explored the possibility that those multiple dimensions could contain two-dimensional membranes, kind of like the film forming the surface of a soap bubble. He and his students derived the math describing such supermembranes living in 11 dimensions (10 of space, one of time).

Maybe, string/brane/M theory would explain the amount of that mysterious “dark” energy in space and all would be well. But no. Working with physicist Raphael Bousso, Polchinski found that string theory did not specify how much energy the vacuum of space contained. Instead the theory predicted a virtually countless number of vacuum states, with nearly any amount of repulsive energy you could imagine. In other words, string theory described a multiverse.

Polchinski’s modesty manifested itself in his reaction to this situation. He hated the idea of a multiverse, because it implied that some questions had no answers that physicists could calculate. No equation could specify the amount of dark energy; it would just be luck — determined by which universe had the right amount of dark energy to make it hospitable to life (an idea known as the anthropic principle).

Interesting Article:
https://www.sciencenews.org/blog/context/remembering-joe-polchinski-modest-physicist-who-conceived-multiverse

#physics #JoePolchinski #stringtheory

Experiments support theory of cosmic magnetic field growth
Researchers have measured the amplification of a magnetic field in a turbulent laboratory plasma, providing the first physical demonstration of a mechanism that is thought to enhance fields in galaxies and galaxy clusters.

Source & further reading:
http://physicstoday.scitation.org/do/10.1063/PT.6.1.20180222a/full/

#physics #plasma #science #magneticfield #space

Beatrice Tinsley
Born on 27 January in 1941, Beatrice Tinsley was an astronomer and cosmologist who made fundamental contributions to our understanding of galaxy formation and evolution. She was born in Chester, England, but grew up in New Zealand and studied math and physics at Canterbury University. She married fellow physics student Brian Tinsley in 1961, and the couple moved to the US in 1963 when Brian accepted an appointment at the University of Texas at Dallas.

As a married woman with career aspirations, Beatrice struggled against gender bias in the male-dominated field of astronomy. Despite earning a PhD in 1967 and performing groundbreaking astronomical research, Beatrice was never able to secure a professorship at UT Dallas. In 1975 Beatrice divorced Brian and took a position at Yale University, where she became the school’s first female astronomy professor in 1978.

Among Tinsley’s many achievements was her synthesis of vast amounts of newly generated space telescope data to model galaxies and chart how they evolve over time. Her work was cut short, however, when she died of cancer at age 40 on 23 March 1981. By that time, Tinsley had published more than 100 scientific papers and become one of the most distinguished astronomers in the US.

In 1986 the American Astronomical Society created the Beatrice M. Tinsley Prize for outstanding creative contributions to astronomy or astrophysics.

Photo credit: AIP Emilio Segrè Visual Archives, gift of Edward Hill
You can read the Physics Today obituary written by Sandra Faber:
http://physicstoday.scitation.org/doi/abs/10.1063/1.2914734

#history #womeninSTEM #science #BeatriceTinsley

Liquids that are less dense than an ideal gas
A water droplet has structural integrity because of attractive forces between water molecules. If the molecules get close enough, however, the intermolecular forces are repulsive; water molecules can pack only so tightly. In quantum systems, intrinsically quantum fluctuations can stabilize a cluster of atoms against collapse. As a result, quantum droplets can have extraordinarily low densities.

Using Bose-Einstein condensates, researches created liquids that have extraordinarily low densities - five orders of magnitude below that of an ideal gas at room temperature and pressure.

Journal article:
http://science.sciencemag.org/content/early/2017/12/13/science.aao5686

Source:
http://physicstoday.scitation.org/do/10.1063/PT.6.1.20180111a/full/

#physics #science #research #quantumdroplets

What If the Big Bang Wasn't the Beginning? New Study Proposes Alternative
Was the universe created with a Big Bang 13.7 billion years ago, or has it been expanding and contracting for eternity? A new paper, inspired by alternative explanations of the physics of black holes, explores the latter possibility, and rejects a core tenant of the Big Bang hypothesis.

The universal origin story known as the Big Bang postulates that, 13.7 billion years ago, our universe emerged from a singularity — a point of infinite density and gravity — and that before this event, space and time did not exist (which means the Big Bang took place at no place and no time).

However, there is no direct evidence of the original singularity. (Collecting information from that first moment of expansion is impossible with current methods.) In the new paper, Brazilian physicist Juliano Cesar Silva Neves argues that the original singularity may never have existed.

Read the article:
https://www.space.com/38982-no-big-bang-bouncing-cosmology-theory.html
http://agencia.fapesp.br/before_the_big_bang/26684/

#physics #BigBang #science #blackhole #universe