Cloaking

[Anthony]

This whole new field of cloaking is pretty cool. Of course, it's a long way away, and of course the most obvious uses are in the military, but the idea itself is ace. Here's a recent article about a type of cloaking at a distance:

http://www.sciencedaily.com/releases/2009/08/090817073508.htm

I saw this guy at the PRIMA conference in Sydney a couple of months ago.

Here's the video they showed:

http://vimeo.com/6092319

The idea of what they're doing is relatively straightforward: just correct for any changes in the light waves caused by the object. The maths, however, is a little more tricky. And like the other type of cloaking (where you hide something in the middle of a device) this only works at long wavelenths at the moment (microwaves and radio waves).

In this case, the wavelength has to be 'long' compared to the object. So to make something invisible to humans, it would have to be a REALLY small object.

But he has some uses in mind for longer wavelengths (in addition to military applications): shielding stuff from earthquakes and tsunamis, which are both just powerful waves. That would be pretty awesome. It seems like this is the new wave of sci-fi come true.

[Nini Ponsaing]

Haha - wave.

[X-man]

Those clever little insects from "A Bug's Life" could slap this on and hide from bats that use echolocation, or 'emo' whales could use it to become even more anti-social.

It would be a real pain in the arse if the Kepler Telescope never found any planets with ETs on them because they had cloaked their planets. Kepler uses the transit method (AKA transit velocity method) to detect exoplanets (planets around other suns), whereby it detects subtle dips in the incoming light from a star when a planet gets in the way. I don't think it's unreasonable that intelligent aliens would know that this would be one of the most effective ways to find distant small, rocky planets, they might use a cloaking device to hide their planets!

Do you think that this sort of cloaking could be used on a planet-sized scale? Or would the wavelength of the light be too short compared to the size of the planet?

It's an awesome idea, but why does everyone always want to hide? Can't we all just come out of the shadows and hug each other? Except the ninjas - they only come out of the shadows to stab.

[Anthony]

Good point, that hadn't occurred to me. You're right that this exact technique probably wouldn't work with visible light (Kepler uses the visible spectrum) on a planet, the wavelength is too short.

But if you had a really long wave (gravitational waves, anyone?) then it could cloak the planet in that spectrum.

But the principle here is just destructive interference, which really isn't that complicated, and will work for waves of any length, so it's not outside the bounds of galactic possibility that planets have anti-Kepler cloaking devices. Those devils.

[TinBane]

What's the go with gravitational waves?
I remember years ago reading about groups trying to detect them. Have they got any closer to doing that? Is it tied into the LHC in some way? Whenever you ask a physicist a curly question, I bet their standard 'get out of jail' card is that they are waiting on the LHC.