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Note the magnets are not attracted to the copper. The physics of the process is explained briefly by thedevguy:
The movement of the magnet induces an electric current in the copper and with electric current comes a magnetic field, which attracts the magnet. The magnet doesn’t stick to the wall as it falls because the induced current, and its corresponding magnetic field, are perfectly distributed so that the magnet feels magnetic force equally from all sides. The magnetic field slows the magnet, but can’t stop its fall because if the magnet stopped moving, the induced electric field would go away and the magnet would start falling again.
Of note, while the magnet is falling slowly, the copper pipe will feel heavier in the hand because the pipe is “holding up” the magnet. I wonder whether the same effect could be observed by dropping buckyballs through a smaller copper tube?
Researchers at the University of Minnesota have created a metal alloy composed of nickel, cobalt, manganese and tin. This “multiferroic composite” can convert heat into electricity!
In this case, the new alloy — Ni45Co5Mn40Sn10 — undergoes a reversible phase transformation, in which one type of solid turns into another type of solid when the temperature changes, according to a news release from the University of Minnesota. Specifically, the alloy goes from being non-magnetic to highly magnetized. The temperature only needs to be raised a small amount for this to happen.
When the warmed alloy is placed near a permanent magnet, like a rare-earth magnet, the alloy’s magnetic force increases suddenly and dramatically. This produces a current in a surrounding coil, according to the researchers, led by aerospace engineering professor Richard James.
One possible application for this alloy is in automobile exhaust pipes, which vent a lot of heat that could be recycled into electric power for the battery. Read more at Popsci. Link -via reddit
Foxes often jump high into the air in order to pounce on prey from above. They have an unusual ability to not only judge the correct direction of attack, but the proper distance to leap in a parabolic arc. How do they do it? Hynek Burda of the University of Duisburg-Essen in Germany speculates that a magnetic spot on their retinas gives them the ability to measure distance:
Burda’s team found that when the foxes could see their prey they jumped from any direction but when prey were hidden, they almost always jumped north-east. Such attacks were successful 72 per cent of the time, compared with 18 per cent of attacks in other directions.
All observers saw the same thing, but Burda remained baffled, until he spoke to John Phillips at Virginia Tech in Blacksburg. Phillips has suggested that animals might use Earth’s magnetic field to measure distance.
The pair think a fox hunts best if it can jump the same distance every time. Burda suggests that it sees a ring of “shadow” on its retina that is darkest towards magnetic north, and just like a normal shadow, always appears to be the same distance ahead. The fox moves forward until the shadow lines up with where the prey’s sounds are coming from, at which point it is a set distance away.
Link via Popular Science | Photo by Flickr user mikebaird used under Creative Commons license
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The Earth’s magnetic field fluctuates in intensity. But until recently, most scientists thought that it wouldn’t change more than 16% in a century. Slag recovered from a 3,000-year old Egyptian copper mine indicates that the magnetic field could double in just 20 years. Ron Shaar of the Hebrew University of Jerusalem explained:
Their measurements, plus theoretical models, showed that the magnetic field’s strength peaked around 3,000 years ago in the middle Egypt’s Iron Age.
“We don’t have volcanic glass in Israel, but we do have slag,” Shaar said. When the ancient Egyptians (in what is now Israel) melted ore to produce copper, they created a lot of leftover molten rock that they threw immediately on a waste heap. The rock cooled quickly, preserving a signature of the magnetic field.[...]
Back in the lab, the team melted and re-froze some of the slag in the presence of a known magnetic field, to make sure they could trust the rock to faithfully trap the field strength. Then they measured the field strength in the raw slag.
They found that the magnetic field abruptly spiked twice during the 180 years they studied, once around 2,990 years ago and once around 2,900 years ago. Both times, the field jumped up in strength and then fell by at least 40 percent in the space of about 20 years.
“These geomagnetic spikes are very different from what we see now or have seen before,” Shaar said
Link via reddit | Photo: unrelated piece of copper slag by the University of California at Irvine
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Medical researchers were able to disrupt the moral judgments of test subjects by subjecting the part of the brain responsible for such decisions to magnetic forces:
For their experiment, the scientists had 20 subjects read several dozen different stories about people with good or bad intentions that resulted in a variety of outcomes.
One typical story was about a boyfriend who leads his girlfriend across a bridge. In some versions, the boyfriend harmlessly walked his girlfriend across the bridge with no ill effect. In other cases, the boyfriend intentionally led the girlfriend along so she would break her ankle. The subjects used a seven point scale — one being forbidden and seven completely permissible — to record whether they through the situation was morally acceptable or not.
While the subjects read the story, the scientists applied a magnetic field using a method known as transcranial magnetic stimulation. The magnetic fields created confusion in the neurons that make up the RTPJ, said Young, causing them to fire off electrical pulses chaotically.
Link via Alphecca | Image: NASA
Charles Q. Choi of Live Science writes that scientists working for NASA used a superconducting magnet that simulates some of the effects of gravity to lift a mouse into the air. The agency has been working on such technology in the hope of alleviating the bone decay that would affect astronauts in zero-gravity environments for prolonged periods of time:
Scientists working on behalf of NASA built a device to simulate variable levels of gravity. It consists of a superconducting magnet that generates a field powerful enough to levitate the water inside living animals, with a space inside warm enough at room temperature and large enough at 2.6 inches wide (6.6 cm) for tiny creatures to float comfortably in during experiments….
Repeated levitation tests showed the mice, even when not sedated, could quickly acclimate to levitation inside the cage. After three or four hours, the mice acted normally, including eating and drinking. The strong magnetic fields did not seem to have any negative impacts on the mice in the short term, and past studies have shown that rats did not suffer from adverse effects after 10 weeks of strong, non-levitating magnetic fields.
“We’re trying to see what kind of physiological impact is due to prolonged microgravity, and also what kind of countermeasures might work against it for astronauts,” Liu said. “If we can contribute to the future human exploration of space, that would be very exciting.” They are now applying for funding for such research with their levitator.
Link via Popular Science
Image: U.S. Department of Energy
Scientists have long speculated about the existence of magnetic materials that have only one pole, instead of both negative and postive poles. Even our resident mad scientist has written about the subject. But now, Claudio Castelnovo of the University of Oxford thinks that his team has found evidence of the existence of these monopoles in certain rare-materials known as “spin ices”:
At low temperatures, there is still some magnetic wiggle room in the spin ice’s lattice structure, but not a lot—the magnetic freedom of the system is frustrated, so to speak. “As a result, this is a substance that has degrees of freedom that look the same, microscopically, as you would see in a fridge magnet,” Castelnovo says. “But a fridge magnet is able to order so as to act as a fridge magnet and stick to metals, while this one is not able to achieve this level of ordering in spite of having this magnetic structure inside, because of this frustration.”
Internally, the tiny magnetic components arrange themselves head to tail in strings, like chains of bar magnets stretching across a table in different directions. In a very cold, clean sample, those strings form closed loops. But excitation induced by a rise in temperature can introduce tiny defects in these chains, Castelnovo says—in the bar-magnet analogue, one of the magnets is flipped, breaking the head-to-tail continuity. “You have your path that is north–south–north–south, and at a certain point one of the needles actually twists 180 degrees and points the wrong way,” he explains.
On either side of that defect, all of a sudden, is a concentration of magnetic charge—two norths at one end, two souths at the other. Those concentrations can float free along the string, acting as—voilà—magnetic monopoles.
Image by flickr user Stinging Eyes used under creative commons license
