Physics prediction finally confirmed

City College of New York Assistant Professor of Physics Cory Dean, who recently arrived from Columbia University where he was a post-doctoral researcher, and research teams from Columbia and three other institutions have definitively proven the existence of an effect known as Hofstadter’s Butterfly.

The phenomenon, a complex pattern of the energy states of electrons that resembles a butterfly, has appeared in physics textbooks as a theoretical concept of quantum mechanics for nearly 40 years. However, it had never been directly observed until now. Confirming its existence may open the door for researchers to uncover completely unknown electrical properties of materials…

Douglas Hofstadter, a physicist and Pulitzer Prize-winning author, first predicted the existence of the butterfly in 1976, when he imagined what would happen to electrons subjected to two forces simultaneously: a magnetic field and the periodic electric field.

The energy spectrum, or pattern of energy levels, that these dueling forces create is said to be “fractal,” that is, infinitely smaller versions of the pattern appear within the main one. This effect is common in classical physics, but rare in the quantum world.

“When you plot the spectrum, it takes on the form of a butterfly. Zoom in on the spectrum and you see the butterfly again, zoom in and see butterfly again,” said Professor Dean. The light and dark sections of the pattern, respectively, correspond to light “gaps” in energy level that electrons cannot cross and dark areas where they can move freely.

“The existence of gaps changes the way electrons move through a material. Copper for example, has no gaps, whereas an insulator, like glass, has very large gaps,” explained Professor Dean. “The relationship between energy and how dense the electrons are in a material – energy density – determines all electrical properties. That’s why copper conducts, glass or ceramic doesn’t, and other materials weakly conduct, like semiconductors.”

“What you see in a Hofstadter spectrum is a very complicated structure of gaps arranged in a fractal pattern,” he continued, which suggests as yet unknown electrical properties.

The team produced the effect by sandwiching together flat sheets of graphene – a single-atom-thickness of carbon – and another material, called boron nitride, and twisting them against each other to create what is called a superlattice. “Graphene has hexagonal chicken wire structure and boron nitride does too,” he said. “It is as if you take screen door material and put one sheet on top of other. As you rotate it you see a periodic pattern appear. You get an interference effect – a ‘moiré’ pattern.” In the case of the chicken-wire structure of graphene and boron nitride, the pattern forms a fractal butterfly of energy states.

Moire patterns drive me nuts. Sometimes I think there must be some pre-industrial part of my brain stuck into dizziness by the phenomenon.

E-readers get heavier with each book – WTF?

E-readers are meant to let bookworms carry their entire libraries with them without any additional weight – but the devices actually get heavier every time a new text is downloaded.

The weight difference is unlikely to make much difference to holidaymakers’ baggage allowances, however, because each new tome is about as heavy as a single molecule of DNA. Filling a 4GB Kindle to its storage limit would increase its weight by a billionth of a billionth of a gram

Prof John Kubiatowicz a computer scientist at the University of California, Berkeley, explained…that storing new data involves holding electrons in a fixed place in the device’s memory.

Although the electrons were already present, keeping them still rather than allowing them to float around takes up extra energy – about a billionth of a microjoule per bit of data.

Using Einstein’s E=mc² formula, which states that energy and mass are directly related, Prof Kubiatowicz calculated that filling a 4GB Kindle to its storage limit would increase its weight by a billionth of a billionth of a gram, or 0.000000000000000001g…

E-readers could also become slightly heavier in the summer, because they would take on more energy from their exposure to sunlight, scientists explained.

Graeme Ackland, of Edinburgh University, told the Guardian: “If Prof Kubiatowicz is really struggling with the extra weight, he is welcome to come to Edinburgh where it’s cooler, and the lack of thermal energy in his Kindle will more than compensate.”

Of course, if we’re going to make comparisons based on geography we should compensate for weight differences between, say, Edinburgh – which probably could grow mildew on stainless steel – and my neck of the prairie with a current annual rainfall less than 7 or 8 inches.

Some of those water molecules may prefer to attach themselves to some plot lines rather than others. 🙂

Bosons aren’t fermions – not even a little bit

Of all the assumptions underlying quantum mechanics and the theory that describes how particles interact at the most elementary level, perhaps the most basic is that particles are either bosons or fermions. Bosons, such as the particles of light called photons, play by one set of rules; fermions, including electrons, play by another.

Seven years ago, University of California, Berkeley, physicists asked a fundamental and potentially disturbing question: Do bosons sometimes play by fermion rules? Specifically, do photons act like bosons all the time, or could they sometimes act like fermions?

Based on the results of their experiment to test this possibility, published June 25 in the journal Physical Review Letters, the answer is a solid “no.”

The theories of physics – including the most comprehensive theory of elementary particles, Quantum Field Theory, which explains nature’s electromagnetic, weak and strong nuclear forces (but not gravity) — rest on fundamental assumptions, said Dmitry Budker, UC Berkeley professor of physics. These assumptions are based on how the real world works, and often produce amazingly precise predictions. But some physicists would like to see them more rigorously tested.

“Tests of (these assumptions) are very important,” said Budker. “Our experiment is distinguished from most other experimental searches for new physics in that others can usually be incorporated into the existing framework of the standard model of particles and forces. What we are testing are some of the fundamental assumptions on which the whole standard model is based…”

“We have this all-important symmetry law in physics, one of the cornerstones of our theoretical understanding, and a lot depends on it,” said Budker, who is also a faculty scientist at Lawrence Berkeley National Laboratory (LBNL). “But we don’t have a simple explanation; we have a complex mathematical proof. This really bothered a lot of physicists, including the late Nobel laureate Richard Feynman.”

“It’s a shame that no simple explanation exists,” said Budker, because it ties together basic assumptions of modern physics. “Among these assumptions are Lorentz invariance, the core tenet of special relativity, and invariance under the CPT (charge-parity-time) transformation, the idea that nature looks the same when time is reversed, space is reflected as in a mirror, and particles are changed into antiparticles. Lorentz invariance results from the entanglement of space and time, such that length and time change in reference frames moving at constant velocity so as to keep the speed of light constant…

Spacetime, causality, and Lorentz invariance are safe,…for now,” English said.

And we know that if there’s one thing most people require, it’s simple explanations.

It’s easier for us to deny something exists or is happening – than to follow a complex series of tests and research through to an even more complex explanation. It may require thought, an education beyond 6th-grade reading levels and a willingness to learn anew.

Giant natural particle accelerators forming above thunderstorms

A lightning researcher at the University of Bath has discovered that during thunderstorms, giant natural particle accelerators can form 40 km above the surface of the Earth…

When particularly intense lightning discharges in thunderstorms coincide with high-energy particles coming in from space (cosmic rays), nature provides the right conditions to form a giant particle accelerator above the thunderclouds…

These are energetic events and for the blink of an eye, the power of the electron beam can be as large as the power of a small nuclear power plant…

The zone above thunderstorms has been a suspected natural particle accelerator since the Scottish physicist and Nobel Prize winner Charles Thomson Rees Wilson speculated about lightning discharges above these storms in 1925.

In the next few years five different planned space missions (the TARANIS, ASIM, CHIBIS, IBUKI and FIREFLY satellites) will be able to measure the energetic particle beams directly.

Dr Martin Fullekrug comments: “It’s intriguing to see that nature creates particle accelerators just a few miles above our heads. Once these new missions study them in more detail from space we should get a far better idea of how they actually work. They provide a fascinating example of the interaction between the Earth and the wider Universe.”

Recently watched a documentary on this phenomenon – minus this latest analysis and understanding – on one of the HD documentary channels. Some superb aerial photography.

RTFA to see how these were predicted and measured.

As natural as these occurrences are – we should be able to get some nutballs going out of their minds on the likelihood of a spontaneous black hole emerging from a thunderstorm and gobbling up the Earth. Or at least Hull.