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New method could hide buildings from earthquakes or tsunamis

Cloaking objects is a big area of research for many scientists. Much of the research is focusing more on cloaking objects from certain types of waves like sound and vibration more than it is focusing on making things invisible to the naked eye.

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."

He 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.

The 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."

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.





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