Thursday, September 18, 2014

Falaco Solitons: Particles at the Pool

While the season for swimming has already passed in most of the country, it’s still not too late in the year for some physics fun in the pool! If you’ve got a sunny day, a dinner plate, and access to a calm body of water, you can explore one of the coolest (and coolest-sounding) phenomena in fluid dynamics: vortical (or “Falaco”) solitons.

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Podcast: The Venus Zone

This week on the Physics Central Podcast, we take a trip to the Venus Zone. You've heard of the Habitable Zone, yes? That's the region around a star where scientists think a planet would receive just the right amount of radiation to support life. The planet would still need an atmosphere and probably some water, but in the Habitable Zone there's a good chance it would also have a reasonable surface temperature.

Now, a group of researchers have defined a Venus Zone, which lies inside the Habitable Zone. The theory goes that a planet in the Venus Zone will receive too much radiation from the home star: with an atmosphere like Earth's, it would cause a runaway greenhouse effect, causing temperatures to soar. That's what happened on the surface of Venus, where temperatures average about 850 degrees Fahrenheit.

That's the theory, anyway. To find out for certain, scientists need to get a look at some planets beyond our own solar system. Stephen Kane, an astronomer at San Francisco State University, and his colleagues have already identified 43 planets in the Venus Zone, using data from the Kepler Space Telescope. Today on the podcast I'll talk to astronomer Kane about the work he and his colleagues have done defining the Venus Zone, and when they'll know for sure if those 43 planets have similarly inhospitable atmospheres.

Learning about planets that look like Venus would also help in the search for planets that look like Earth. And, it might help us better understand our own climate here at home.

Kane has a great website all about the Venus Zone, so be sure to check it out.
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Friday, September 12, 2014

Pebbly Space Particles May Kick-start Formation Of Planets And Stars

Curiously large dust grains may contribute to development of bodies in space.
The Orion Nebula, courtesy of NASA
Interstellar space can be a dusty place, filled with tiny flecks no bigger than a bacterial cell.

But now astronomers have detected particles as big as pebbles, possibly a previously unknown type of dust that may kick-start the production of planets. The presence of these big particles may also suggest that star formation is more efficient than previously thought.

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Thursday, September 11, 2014

Galaxies Writ Small

Courtesy imgur user ScienceLlama

At a glance, it’s easy to tell that something’s not right with the galaxies and clusters in these images from deep space, but it might sound silly when it’s put into words: they’re little! The photographic technique of miniature faking takes advantage of the way light is focused by a lens to trick your brain into perceiving something that’s thousands of light-years across as being small enough to fit into the palm of your hand. 

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Podcast: The History of the Helium Crisis

In the 1990's, the US Bureau of Land Management unintentionally became the worlds largest supplier of helium. Last year, the world faced a potential helium cliff, when the US government had to decide whether to keep selling helium or exit the market as they'd originally planned. 

Thankfully, the crisis was averted; this last July the US started auctioning off large chunks of its helium to other suppliers, in an effort to keep the helium market healthy. 

Today on the Phyiscs Central podcast, we're talking about helium and the very important role it plays for many physicists around the world. We'll talk about how the helium market got to the edge of that economic cliff, why some physicists rely so heavily on helium, and what they're doing now to survive in the helium market.

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Monday, September 08, 2014

Breaking Beautiful

Researchers have found out how orderly patterns of cracks form atop electronics.

Originally published: Aug 29 2014 - 3:00pm, Inside Science News Service
By: Gabriel Popkin, Contributor

(Inside Science) -- Repeating crescents, snail shell-like spirals and a jumble of shapes resembling a Keith Haring painting: These patterns and more can start to adorn old paintings, pottery glazes and even electronics under the right conditions. Now, a team of scientists from France and Chile has revealed the potentially useful mechanism that causes these beautiful but often damaging cracks.

“I think it’s very creative work,” said John Hutchinson, a mechanical engineer at Harvard University in Cambridge, Massachusetts. “These crack patterns are extraordinary.”

The research team first learned about crescent-shaped cracks from a physicist at the Ecole Normale Supérieure de Cachan in France; she noticed the cracks forming on tiny optical devices she had designed. The team then discovered other examples of unusual, highly ordered cracks in previously published papers by different research groups. Some of these patterns had apparently gone unnoticed even by the authors of those studies.

High resolution photograph of cracks in thin layer of glass atop a silicon wafer. The colors come from optical interference between the thin wafer and the glass above.
Image Credit and Copyright: Joël Marthelot (ESPCI) et al./PRL

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Thursday, September 04, 2014

Build Your Own Time-Warp Tube!

If you spend much time browsing home-science channels on youtube, you’ve probably seen videos of what happens when you drop a magnet through a metal tube. If not, enjoy this mind-bending display of Eddy Current Braking

While it might be difficult to get your hands on such a large magnet and pipe, the phenomenon will occur with a tube of any size, as long as it’s made of a sufficiently conductive material and your magnet is powerful enough. While magnets will ordinarily only stick to metals that contain one of the three ferromagnetic elements, Iron, Nickel, or Cobalt, this effect has nothing to do with that “stickiness”; it arises from a different property of electromagnetism known as Lenz’s law, which is related to Faraday’s law of induction. Faraday’s law states that a changing electromagnetic field creates an electric current, and vice versa; a changing electric current creates a magnetic field.

Image courtesy of Bored of Studies
If you’ve ever used a shake-powered flashlight, you’ve seen these two laws in action; the motion of a magnet back and forth through the spiraling copper coils inside the device creates an electric current, which can charge a battery or power a small LED. It may be tempting to think of it as the magnet “dragging” a small number of electrons through the metal back and forth with it, but the reality of the situation is slightly different. The change in magnetic field strength as you shake the flashlight back and forth induces a circular current perpendicular to the direction of the magnet’s motion; that is, around the barrel of the flashlight. This is why the spiral shape (and insulation) of the conductive coils is necessary; in trying to travel around the magnet, the current is also forced toward one end of the wire.

If you apply this principle to a copper tube, though, the electrons can make a full circuit without moving one way or the other. As the magnet falls and its field grows stronger in the portion of pipe below it, a “ring” of current is generated around the tube. That increase in electric current, correspondingly, creates a magnetic field, which repels the magnet and slows its fall. Trailing the magnet, the current grows weaker, but since it’s the change in electric current that creates magnetic effects, this too acts to slow the magnet’s fall, this time by attracting it from above.

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Wednesday, September 03, 2014

Podcast: Entangled Photons Illuminate an Object Without Touching It

This week on the podcast, things get a bit bizarre. I'm talking with physicist Gabriela Barreto Lemos about a new imaging technique where the photons that "see" an object are never collected by the camera; and the photons that create the image never interact with the object. Here's another way to think about it: imagine I want to see an object, so I shine a flashlight on it. But I don't look at the flashlight beam. Instead I shine a second light in the opposite direction, and that second flashlight shows me the object. (*This is a rough analogy, even though the experiment is equally weird).

How is such a thing possible? This counterintuitive set up utilizes two properties of quantum mechanics: entanglement and indistinguishability. Ours is a strange, strange world when quantum mechanics is involved, and this is no except.

Listen to the podcast to hear more.

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Friday, August 29, 2014

Highlights from 25 Years of Cold Fusion Research

Back in 1989, Stanley Pons  and Martin Fleischmann stunned the world by announcing a new form of fusion that could take place at nearly room temperature. That's not particularly cold, but it's much colder than the temperatures of the sun, fusion bombs, and most controllable fusion proposals. On March 23 in '89, cold fusion was born.

I still have a copy of the very first paper Pons and Fleischmann released. It had been faxed (yep faxed!) from lab to lab in universities across the US and around the world. Many technical details were omitted, presumably because the cold fusion pioneers were eager to turn the revolutionary discovery loose to make the world a better place.

In honor of a quarter century cold fusion research, I've compiled the top ten advances in the field since that momentous spring day.

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Thursday, August 28, 2014

"Water Tractor Beam" Makes a Splash

A new paper from researchers at the Australian National University is making waves in physics this month; the group claims to have developed a “tractor beam” of sorts. However, as is usual for claims of science-fiction technology made real, there’s a catch—it won’t be useful for pulling in rogue spaceships, but it might one day find applications helping guide the path of steamships. The report details the creation of never-before-seen flow patterns using waves on the surface of water in a shallow tank that, paradoxically, draw objects toward the wave source.

Counter-spiraling whirlpools create an axis along which floating objects will be drawn in. The water is ejected laterally, in the chaotic squiggly region.

The new technique relies on mechanically-driven buoys that oscillate up and down at a certain frequency to create stable whorl-like patterns of flow, which draw in surface particles from a particular direction. By changing the shape, size, and oscillation speed of the buoys, the team managed to create a variety of flow patterns, one of which displayed the unique pulling effect described in the paper. The most effective “tractor beam” arrangement used a cylindrical oscillator, oriented like a floating log, to make standing waves. While plane waves (below, left) can only move objects away from the source, under the right circumstances they can reflect off the boundaries of the tank to create peaked, three-dimensional waves (below, right), which lead to the unprecedented phenomenon.

Plane waves extend to the edges of the container laterally, but the more exotic waves created in this experiment are described as fully three-dimensional.

Further experiments with different buoy shapes led to the creation of unexpected and interesting flow dynamics, which may lead to advances in the study of fluid vortexes, but only the cylindrical oscillator produced the reported pulling effect. And while it is difficult to imagine finding a large body of water with conditions suitable to recreate the experiment, the paper's authors hope that the work may someday see use in the containment of oil spills and other surface contaminants.

Bizarre flow dynamics emerge when a conical “plunger” is used.
All images credit H. Punzmann, et al, Australian National University.

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Podcast: August News Round-Up

This week on the Physics Central Podcast, we have our monthly news round-up. It's a mostly space-themed show this month. First up, the biggest astronomy news of the summer: after 10 years of travel, the Rosetta spacecraft has finally reached the comet 67P/Churyumov-Gerasimenko. Rosetta will be the first space craft to study a comet up close and for an extended period of time.

In other news, could the Brazil-nut effect be responsible for speckled asteroids? Is there a new dark matter signal out there? And finally, why would an atomic clock on board the International Space Station measure time differently than on earth?

Listen to the podcast to hear answers to these questions and more.

By the way, you can now send your deceased pet's ashes to space.
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Tuesday, August 26, 2014

Woodpecker Bodies Cushion Collision Impact On Bird Brains

Originally published: Aug 25 2014 - 10:30am, Inside Science News Service
By: Katharine Gammon, Contributor

(Inside Science) -- Woodpeckers are some of the most industrious birds in nature. Their intense tapping -- all an elaborate effort to procure food -- can happen as rapidly as 20 pecks per second, with each strike transmitting a seemingly brain-rattling force of up to 1,200 times the force of gravity at Earth's surface.

Yet, despite those repetitive impacts, woodpeckers typically show none of the typical signs of head trauma. How do their brains endure this?

Their remarkable ability to absorb shock has made woodpeckers a favorite species to study for biology-inspired materials and design. Now, a new analysis shows that the bird's body stores most of the energy created in the pecking – and the understanding could lead to better helmets, cars or armor.

Wu Chengwei, a mechanical engineer at Dalian University of Technology in northeastern China, used CT scans of the birds' bodies to create a precise 3D model of the creature. Working with colleagues, he ran computer models and found that 99.7 percent of the energy generated in pecking was stored in the form of strain energy, which spread out the force over the bird's body. Only a tiny leftover fraction of the energy went into the bird's brain.

Image credit: vastateparksstaff via flickr |
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Monday, August 25, 2014

A Better Way to Build a Pyramid?

The Egyptian pyramids are some amazing works of engineering. The biggest, the Great Pyramid at Giza, held the record for nearly 3,800 years as the tallest man-made structure in the world. What's astounding is that each limestone and granite block weighing up to eighty tons had to be dragged from quarries miles away, then hoisted up to 400 feet before finally being laid in place. 

Two of the pyramids at Giza. Image: Ed Yourdon via WikimediaCommons

Doing that for one stone takes an immense amount of manpower; repeating that for hundreds of thousands of slabs boggles the mind. The archeological consensus holds that huge crews of workers dragged the immense stones on sleds.

Maybe they should have tried rolling the stones is what Joseph West of Indiana State University is proposing. He and his undergraduate students Gregory Gallagher and Kevin Waters posted an idea on the ArXiv the other week for a simple way to roll a rectangle.

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