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Sunday, July 31, 2011 1:26 PM


Weekend Diversions: "Spectacular" Double Meteor Shower This Week; Space-Time Cloak Could Make Events Disappear; Invisibility Cloaks from Calcite


Had enough of the debt ceiling fiasco? If so here are a few interesting weekend diversions courtesy of National Geographic.

"Spectacular" Double Meteor Shower This Week

One of the best shooting star events of the year is the annual August Perseid meteor shower. However this year's peak, on August 12, happens to coincide with a bright full moon—drastically cutting down the number of meteors visible to the naked eye.



Yet while the main event might be blocked out by the blinding moonlight, the opening act promises to be much better.

This year the lesser known Delta Aquarid meteor shower is expected to peak on Friday night, when the Delta Aquarids' more productive Perseid cousin is just starting to ramp up.

Together the showers will produce anywhere between 15 and 30 shooting stars per hour under clear, dark skies.

On average, the Perseids begin falling at a rate of around five meteors per hour. They're visible for a couple of weeks before mid-August, when they peak at hourly rates of 60 to 120 meteors.

Most people around the world can see the showers, best seen with the naked eye in a dark, rural area away from city lights. Since meteors will be streaking across the overhead skies, lie down on a blanket or recline in a lawn chair and allow your eyes to become adapted to the darkness, Samra suggested.

"Meteor shower activity always increases as the night progresses towards dawn. If you are a night owl, then staying up to catch a more spectacular show might be worth it."

But all may not be lost with the Perseids—observing the sky show a few days before the August 12 peak may work too, noted astronomer Geza Gyuk of the Adler Plaentarium in Chicago.

"For example, on the night of the ninth, morning of the tenth, there will be a couple hours after the moon has set [about 2 a.m. local time] and before the morning twilight begins when it's close enough to the peak that one might expect 15 per hour."

"They are also known for the occasional nice fireball with a long-lasting 'smoke trail,'" Gyuk said. "If we get more of these than usual, then even moonlight won't spoil the fun."
Perseid Pictures: Meteor Shower Dazzles Every August



One of many images in the link.

Space-Time Cloak Possible, Could Make Events Disappear?
It's no illusion: Science has found a way to make not just objects but entire events disappear, experts say.



According to new research by British physicists, it's theoretically possible to create a material that can hide an entire bank heist from human eyes and surveillance cameras.

"The concepts are basically quite simple," said Paul Kinsler, a physicist at Imperial College London, who created the idea with colleagues Martin McCall and Alberto Favaro.

Unlike invisibility cloaks—some of which have been made to work at very small scales—the event cloak would do more than bend light around an object.

(Also see "Acoustic 'Invisibility' Cloaks Possible, Study Says.")

Instead this cloak would use special materials filled with metallic arrays designed to adjust the speed of light passing through.

In theory, the cloak would slow down light coming into the robbery scene while the safecracker is at work. When the robbery is complete, the process would be reversed, with the slowed light now racing to catch back up.

If the "before" and "after" visions are seamlessly stitched together, there should be no visible trace that anything untoward has happened. One second there's a closed safe, and the next second the safe has been emptied.

Currently, nobody knows how to do that except in fiber optics, in which the speed of a signal can be varied by a few percent by changing the intensity of the light.

There are still a few hitches to address, though, before attempting such an experiment, according to the University of St. Andrews's Leonhardt.

For instance, being able to cloak an event lasting more than a few femtoseconds—one-millionth of a nanosecond—would require light from an immensely powerful laser, he said.

"The experiment is not entirely impossible, but it is at the limit of what one can do with present technology in an ordinary university laboratory," Leonhardt said.
New Invisibility Cloak Closer to Working "Magic"


A pink object seems to vanish behind a chunk of calcite, underwater and illuminated by green light.

Harry Potter and Bilbo Baggins, take note: Scientists are a step closer to conquering the "magic" of invisibility.

Many earlier cloaking systems turned objects "invisible" only under wavelengths of light that the human eye can't see. Others could conceal only microscopic objects. (See "Two New Cloaking Devices Close In on True Invisibility.")

But the new system, developed at Massachusetts Institute of Technology and the Singapore-MIT Alliance for Research and Technology (SMART) Centre, works in visible light and can hide objects big enough to see with the naked eye.

The "cloak" is made from two pieces of calcite crystal—a cheap, easily obtained mineral—stuck together in a certain configuration.

Calcite is highly anisotropic, which means that light coming from one side will exit at a different angle than light entering from another side. By using two different pieces of calcite, the researchers were able to bend light around a solid object placed between the crystals.

"Under the assembly there is a wedge-shaped gap," said MIT's George Barbastathis, who helped develop the new system. "The idea is that whatever you put under this gap, it looks from the outside like it is not there."
It is quite amazing the stuff scientists are working on and the images from National Geographic are spectacular. Inquiring minds will want to give some of those articles a closer look.

My weekend diversion is gardening and golf.

Mike "Mish" Shedlock
http://globaleconomicanalysis.blogspot.com
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