Atom-Scale Ohmmeter

A highly stable scanning tunneling microscope measures the electrical properties of a metal on a scale smaller than individual atoms.

A gentle touch. The needle-like tip of a scanning tunneling microscope (STM) terminates in a single atom that can touch a surface at different locations, such as on top of an atom (left) or in the “hollow” between three atoms (right). A highly stable STM that touches the surface without damaging it can measure the differences in electrical conductance among several different types of sites.

A gentle touch. The needle-like tip of a scanning tunneling microscope (STM) terminates in a single atom that can touch a surface at different locations, such as on top of an atom (left) or in the “hollow” between three atoms (right). A highly stable STM that touches the surface without damaging it can measure the differences in electrical conductance among several different types of sites.

A scanning tunneling microscope (STM) can make an image of individual atoms on a surface or move single atoms around. Now researchers have pushed the device’s precision and used it to measure the differences in electrical conductance between different locations around a single atom on a lead surface. The results could help elucidate the properties of metals and superconductors and might one day find use in nanotechnology fabrication.

An STM brings a needle-like probe—the tip of which is a single atom—extremely close to a sample surface in a vacuum. When voltage is applied, electrons can jump, or “tunnel,” across the gap, and measuring the resulting current while moving the tip across the surface leads to an image. In another STM technique, the probe tip touches the sample, allowing atoms to chemically bond with it. Researchers have used this method, known as point contact, to move atoms around like toy blocks. The point contact technique would also be appropriate for measuring electrical conductance of a material at the atomic scale, to learn how current flows in the quantum regime, where the classical Ohm’s law fails. Continue reading Atom-Scale Ohmmeter

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Quantum physics: What is really real?

A wave of experiments is probing the root of quantum weirdness.

An experiment showing that oil droplets can be propelled across a fluid bath by the waves they generate has prompted physicists to reconsider the idea that something similar allows particles to behave like waves.

An experiment showing that oil droplets can be propelled across a fluid bath by the waves they generate has prompted physicists to reconsider the idea that something similar allows particles to behave like waves.

Owen Maroney worries that physicists have spent the better part of a century engaging in fraud.

Ever since they invented quantum theory in the early 1900s, explains Maroney, who is himself a physicist at the University of Oxford, UK, they have been talking about how strange it is — how it allows particles and atoms to move in many directions at once, for example, or to spin clockwise and anticlockwise simultaneously. But talk is not proof, says Maroney. “If we tell the public that quantum theory is weird, we better go out and test that’s actually true,” he says. “Otherwise we’re not doing science, we’re just explaining some funny squiggles on a blackboard.”
QM2
It is this sentiment that has led Maroney and others to develop a new series of experiments to uncover the nature of the wavefunction — the mysterious entity that lies at the heart of quantum weirdness. On paper, the wavefunction is simply a mathematical object that physicists denote with the Greek letter psi (Ψ) — one of Maroney’s funny squiggles — and use to describe a particle’s quantum behaviour. Depending on the experiment, the wavefunction allows them to calculate the probability of observing an electron at any particular location, or the chances that its spin is oriented up or down. But the mathematics shed no light on what a wavefunction truly is. Is it a physical thing? Or just a calculating tool for handling an observer’s ignorance about the world?

Read more at http://www.nature.com/news/quantum-physics-what-is-really-real-1.17585

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Type 1a Supernova Animation


Animation showing a binary star system in which a white dwarf accretes matter from a normal companion star. Matter streaming from the red star accumulates on the white dwarf until the dwarf explodes. With its partner destroyed, the normal star careens into space. This scenario results in what astronomers refer to as a Type Ia supernova.
Read also: NASA Spacecraft Capture Rare, Early Moments of Baby Supernovae

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A brief history of physics education in the United States

HS physicsIn order to provide insight into current physics teaching practices and recommended reforms, we outline the history of physics education in the United States—and the accompanying pedagogical issues and debates—over the period 1860–2014. We identify key events, personalities, and issues for each of ten separate time periods, comparing and contrasting the outlooks and viewpoints of the different eras.

This discussion should help physics educators to (1) become aware of previous research in physics education and of the major efforts to transform physics instruction that have taken place in the U.S., (2) place the national reform movements of today, as well as current physics education research, in the context of past efforts, and (3) evaluate the effectiveness of various education transformation efforts of the past, so as better to determine what reform methods might have the greatest chances of success in the future…
… Read more at physicseducation.net

The Unruh effect and oscillating neutrinos

Dharam Vir Ahluwalia, Lance Labun, Giorgio Torrieri
We point out that neutrino oscillations imply an ambiguity in the definition of the vacuum and the coupling to gravity, with experimentally observable consequences due to the Unruh effect.
In an accelerating frame, the detector should see a bath of mass Eigenstates neutrinos. In inertial processes, neutrinos are produced and absorbed as charge Eigenstates.
The two cannot be reconciled by a spacetime coordinate transformation. This makes manifestations of the Unruh effect in neutrino physics a promising probe of both neutrinos and fundamental quantum field theory.
In this respect, we suggest p→n+ℓ+ (ℓ+=e+++) transitions in strong electromagnetic fields as a promising avenue of investigation.
In this essay we discuss this process both in the inertial and comoving frame, we briefly describe the experimental realization and its challenges, and close by speculating on possible results of such an experiment in different scenarios of fundamental neutrino physics…
… Read more at http://arxiv.org/pdf/1505.04082v1.pdf

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Nuclear War from a Cosmic Perspective

 We humans have invested great resources and ingenuity in building the Spectacular  Thermonuclear Unpredictable Population Incineration Device, (acronym S.T.U.P.I.D.), whose two adjustable knobs determine its explosive power X and the probability P that it goes off spontaneously in any given year.

We humans have invested great resources and ingenuity in building the Spectacular Thermonuclear Unpredictable Population Incineration Device, (acronym S.T.U.P.I.D.), whose two adjustable knobs determine its explosive power X and the probability P that it goes off pontaneously in any given year.

Max Tegmark
I discuss the impact of computer progress on nuclear war policy, both by enabling more accurate nuclear winter simulations and by affecting the probability of war starting accidentally. I argue that from a cosmic perspective, humanity’s track record of risk mitigation is inexcusably pathetic, jeopardizing the potential for life to flourish for billions of years.
Read more at http://arxiv.org/pdf/1505.00246v1.pdf

Found: giant spirals in space that could explain our existence

fermiGiant magnetic spirals in the sky could explain why there is something rather than nothing in the universe, according to an analysis of data from NASA’s Fermi space telescope.

Our best theories of physics imply we shouldn’t be here. The Big Bang ought to have produced equal amounts of matter and antimatter particles, which would almost immediately annihilate each other, leaving nothing but light.

So the reality that we are here – and there seems to be very little antimatter around – is one of the biggest unsolved mysteries in physics. Continue reading Found: giant spirals in space that could explain our existence