A researcher for the University of Utah named
Graeme Milton has developed a new
cloaking method that may someday allow buildings and other large
objects to be shielded from things like sonar, radar, earthquakes,
and even tsunamis.
Milton said, "We have shown that it is
numerically possible to cloak objects of any shape that lie outside
the cloaking devices, not just from single-frequency waves, but from
actual pulses generated by a multi-frequency source."
continued, "It's a brand new method of cloaking. It is
two-dimensional, but we believe it can be extended easily to three
dimensions, meaning real objects could be cloaked. It's called active
cloaking, which means it uses devices that actively generate
electromagnetic fields rather than being composed of 'metamaterials'
[exotic metallic substances] that passively shield objects from
passing electromagnetic waves."
Milton's new breakthrough
will allow for the cloaking of objects much larger than a few
particles. Milton says that radar microwaves move on a wavelength of
about four inches so using his cloaking method an object of about
40-inches could be hidden. The scientists have been able to cloak a
copper cylinder about an inch wide in experiments so far.
cloaking method may be used to cloak objects from incoming waves like
sound waves, sea waves, and seismic waves. This may one day lead to
the ability to cloak buildings from earthquakes, oil rigs form
tsunamis, and submarines
from sonar. The researchers do acknowledge that practical optical
cloaking for invisibility is years away.
The first cloaking
technologies used metamaterials to cloak objects. Milton's new
cloaking method sea waves to cancel out other waves. He said, "The
problem with metamaterials is that their behavior depends strongly on
the frequency you are trying to cloak from. So it is difficult to
obtain broadband cloaking. Maybe you'd be invisible to red light, but
people would see you in blue light."
devices uses "destructive interference" and is very similar
in principal to the noise cancellation headphones many people use on
long air flights.
quote: Milton's cloaking devices uses "destructive interference" and is very similar in principal to the noise cancellation headphones many people use on long air flights.
quote: by Chernobyl68 on August 17, 2009 at 6:51 PMquote:Milton's cloaking devices uses "destructive interference" and is very similar in principal to the noise cancellation headphones many people use on long air flights.So, to cancel out an earthquake, we need an earthquake?
quote: So, to cancel out an earthquake, we need an earthquake?
quote: Who knows this might even lead to active noise cancelation of ambient sound, making passive sonar (listening for the noise the target produces) much more difficult.
quote: Cloaking the effect of a nuke would probably not be practical. This is an adaptation of active noise cancellation. You hit a tsunami wavefront with an identical tsunami that is 180 degrees out of phase and voila both disappear.
quote: ...you would need to apply only as much energy as is being applied to the structure.
quote: ...until actually required, it would be much like a passive implementation.
quote: The power input to large buildings (those which would most benefit from said cloak) could be quite large.
quote: I'd also assume that you'd need substantial local energy storage, as the electric grid probably wouldn't be able to deliver that much instantaneous power.