This is quick survey of present experiments on the physics
of cloaking. Pay attention to the last
piece particularly because it approaches the real thing. Been slightly out of time just may do it in
some weird sort of way.
The best hard evidence for cloaking comes from near
sightings of UFOs who have a clear cause not to be seen in daylight. There is plenty of evidence in those
sightings and they conform to a sometimes vulnerable method that allows
observation.
Even one of the first recorded UFO sightings displayed a odd
fading in and out as the method described in the last part of this article would
likely show.
Thus UFO observations strongly encourage the search for
cloaking.
Invisibility gets a reality check
Harry Potter (Daniel Radcliffe) and the goblin banker Griphook (Warwick Davis
By Alan Boyle
Harry Potter's invisibility cloak comes in handy for the
final installment of the boy wizard's film saga, but real-life
invisibility technologies might well be at least as useful — even if they
aren't as cool as Harry's cloak.
For the foreseeable future, the benefits provided by the real-life
gizmos that have come to be called "invisibility cloaks" or
"cloaking devices" really won't have much to do with the kind of
tricks you'll see in "Harry
Potter and the Deathly Hallows: Part 2." Sorry to
disappoint, but you won't be able to throw a high-tech fabric over your head
and disappear from the scene when the bad guys come looking for you.
However, it is conceivable that scientists could look at
viruses and protein molecules directly, using new breeds of
ultra-high-resolution "superlenses." Physicians might have more
accurate ultrasound scanners at their disposal. Acoustical
cloaks could hide ships or underwater
assets from sonar detection. And offshore facilities could be
engineered to soften the effects of wave erosion on the shore ... or
amplify ocean waves for generating renewable power.
All this magic could come about through the power of metamaterials.
These are materials that are specially structured and shaped to bend
electromagnetic waves or acoustical waves in weird ways. Real-life
invisibility cloaks, for example, are actually devices or layers of
material designed to divert light around the object that's concealed.
This month's issue of Physics World delves into the past, present and
future of invisibility — and the best part about this particular issue is
that you can download it for free as a PDF file.
One of the limiting factors for invisibility cloaks has to do with
wavelength. Shorter wavelengths require smaller structures in order to produce
the bending effect. That's why bending sound waves is easier than bending
electromagnetic waves, and why bending microwaves is easier than bending
visible light. Scientists have been able to develop "invisibility
carpets" that can render bumps in the carpet undetectable —
but the bumps have to be so tiny that you couldn't see them with the naked eye
anyway (on the order of a millionth of a meter), and the invisibility effect
only works for near-infrared wavelengths.
A
different research team came up with a way to hide objects in a
region about three-quarters of an inch wide, using calcite crystals, but the
invisibility effect is produced only with respect to light of a specific
polarization.
"While what has been so far achieved in invisibility science has
been a tour de force of physics and engineering, our children will probably
still have to wait some time for that real Harry Potter cloak," Stanford
University's Wenshan Cai and Purdue's Vladimir Shalaev write in Physics World.
Metamaterials aren't the only way to achieve invisibility, however.
There are also active-camouflage techniques, ranging from video projection
to a high-tech light-emitting matrix that's inspired by a squid's skin.
The latest scientific buzz focuses on space-time cloaking, which
involves using "time lenses" to compress and then decompress light.
This would result in an apparent time gap during which an event could
go unobserved. Scientists have discussed time cloaking as a
theoretical possibility for quite some time (so to speak), but researchers
led by Cornell University physicist Moti Fridman say they actually
created a "time hole" that lasted 15 trillionths of a
second. The
Guardian, the Physics
arXiv Blog and Science News delve into the details.
For much, much more about metamaterials, event cloaking, active
camouflage and other real-life magic spells, check out Physics World's special
issue as well as these links:
Connect with the Cosmic
Log community by "liking" the log's Facebook page or
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out "The
Case for Pluto," my book about the controversial dwarf planet and
the search for new worlds.
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