Universal mirrors: more useful, less fun than carnival mirrors

You know those invisibility cloaks scientists have been struggling to master for decades? This here is said cloak's perfect opposite, and it's bending our minds in ways you can hardly fathom. Ulf Leonhardt, a professor at the University of St. Andrews, has worked with a brilliant team of scientists in order to construct what he calls a universal mirror, or if we're being proper, an omnidirectional retroreflector. Unlike conventional mirrors which simply reflect objects at 90 degrees, this concoction reflects objects back at any angle. In other words, a device such as this would make aircraft, boats and satellites entirely easier to track with radar, but it'll have to mature quite a bit before it's ready for that kind of action. The current build is just a single centimeter high and ten centimeters in diameter, and as with invisibility cloaks, the main ingredient here is metamaterials that we won't pretend to fully understand. Just one word of caution, boffins -- don't let Geek Squad get ahold of this stuff.

[Image courtesy of Barbara Rich, thanks JR]

[carl.frolund @ Jul 20th 2009 6:45AM]

Ehh, sorry this unintelligent comment but can someone clarify what this is about? It seems pretty cool but I don't really understand...

[eGGnext @ Jul 20th 2009 7:19AM]

This technology makes it possible to reflect light right back to the source, no matter the angle it hits the mirror with. When you look at a regular mirror, you only see your own reflection when you're in front of it, but if you look at it at any other angle, you see what's at that same angle to the opposite side of the mirror. This wouldn't happen with this technology. For example, if they used it for a car rearview mirror, you wouldn't be able to see other cars, just yourself, no matter at what angle you tilt the mirror.

"A universal mirror would serve a variety of purposes. Installed on aircraft, boats or satellites, a universal mirror would makes these objects easier to track with radar. When radio waves ordinarily hit these objects, they scatter in many different directions, and only a few radio waves bounce back to the original source of the radar.With a radio universal mirror, all the radio waves would bounce back to their original source, making them much easier to detect and giving the object a much larger radio profile"

[Carl @ Jul 20th 2009 8:25AM]

@eGGnext
Thanks a lot!

[mschaffer @ Jul 20th 2009 9:31AM]

I believe that this is just another retroreflector. These things have been around for decades.
See Wikipedia: http://en.wikipedia.org/wiki/Retroreflector

[DAATMAN @ Jul 20th 2009 6:51AM]

Mirrors are more fun than television.

[Agent .25i @ Jul 20th 2009 10:26AM]

Better looking too.

[B3astofthe3ast @ Jul 20th 2009 7:03AM]

What are some potential uses for this in the world of technology other than aircraft tracking? TVs perhaps, i dont know.

[Mike @ Jul 20th 2009 7:09AM]

I think the images on these sites are misleading, if you were to actually look into a mirror that only reflects light back from the direction it came, you'd just see your eyes, because the only light rays that are reaching your eye have to have come from the same path before it bounced off the mirror.

[Darwin @ Jul 20th 2009 7:14AM]

Yes, and that would be really, really odd, unless of course what they mean is that the light rays come back, along with a bunch of other rays, as if the mirror were perfectly oriented towards you.

Which seems to beg the question of why can't a field-array of tiny corner mirrors be made and what would the effect of that be?

[Newone @ Jul 20th 2009 8:50AM]

That's what I thought.

Moreover, you can buy devices with similar function. It's called Retroreflector, check it out in wikipedia.

[dg @ Jul 20th 2009 2:19PM]

Actually, if this works the way it was explained here, you wouldn't see anything. It would just be black. There's got to be more to it than what was written here, which I must say was a pretty poorly executed article.

If you're going o talk about something like this, at least give us a basic understanding of WHAT IT IS!

[Chris Kanis @ Jul 20th 2009 7:09AM]

"Unlike conventional mirrors which simply reflect objects at 90 degrees...."

?

That doesn't sound right. What about, "Angle of incidence equals angle of reflection?" Perhaps I don't understand what the author means.

[dg @ Jul 20th 2009 2:23PM]

Honestly, engadget, please fix the comment system. That was supposed to go to Mike's comment directly above.

[Fred @ Jul 20th 2009 7:21AM]

If a mirror reflected at 90 degree angles, wouldn't that mean you would never be able to see yourself in it?

[glamajamma @ Jul 20th 2009 8:01AM]

Yes. Thought the same thing when I read that.

[Brandon L @ Jul 20th 2009 9:41AM]

"Unlike conventional mirrors which simply reflect objects at 90 degrees, this concoction reflects objects back at any angle."

I thought mirrors reflected light, not objects.

"If a mirror reflected at 90 degree angles, wouldn't that mean you would never be able to see yourself in it?"

It's 90 degrees from the angle of origin, which doesn't apply when you're directly in front of the mirror.

[Agent .25i @ Jul 20th 2009 10:30AM]

Get a flashlight, go to mirror. Point it at an angle towards the mirror. The light is reflected off by 90 degrees from the angle of the original light beam.

[cardinal @ Jul 20th 2009 11:56AM]

The above 2 comments, in addition to the article, are completely wrong. Mirrors do not reflect light at 90 degrees to any "angle of origin." If you point a flashlight at 20 degrees relative to the normal (perpendicular line to the mirror), the reflected beam will be 20 degrees relative to the normal on the opposite side of the incident beam. There will be 40 degrees between the incident and reflected beams, and this varies with the incident angle.

[G @ Jul 20th 2009 7:34AM]

pics or it didn't happen

[maball54 @ Jul 20th 2009 8:36AM]

I think its "Screenshot or it didn't happen"

[Ian Williams @ Jul 20th 2009 7:42AM]

Slightly off topic, but the office I'm currently sitting in is a couple of hundred yards from the skymirror shown in the photograph.

....I didn't expect to see a photo of Nottingham on engadeget! :)

[Dobba @ Jul 20th 2009 12:54PM]

Yeah - I had to take a second look. It's outside the Nottingham Playhouse - Robin Hood land, actually a stone's throw away from Nottingham Castle. Look - there goes Kevin Costner! ;-)

[Derek @ Jul 20th 2009 7:51AM]

"In other words, a device such as this would make aircraft, boats and satellites entirely easier to track with radar."

Which is why nobody will ever attach one to their aircraft, boat, or satellite.

[Jake @ Jul 20th 2009 8:36AM]

For anyone interested, I was able to find the real paper here: http://www.physics.nus.edu.sg/corporate/research/res_paper/nmat2489.pdf

[Michael @ Jul 20th 2009 8:53AM]

So in other words, if I'm shooting a scene in a movie of a girl in front of a mirror, it doesn't matter where I put my camera because I'll see it in the shot?

Great.
/s

[Jake @ Jul 20th 2009 9:01AM]

Not really. No matter where you put the camera, the camera will see itself in the mirror.

[Michael @ Jul 20th 2009 9:10AM]

@Jake
That's what I said.

[Carl @ Jul 20th 2009 9:15AM]

@Michael
Not quite, what Jakes mean is that the camera would ONLY see itself. Every pixel in the photo would seeing itself. Really, this is blowing my mind. Can we see a picture of what this would actually look like?

[Pardik @ Jul 20th 2009 10:38AM]

Looks like someone has told author about conventional retroreflectors, (mirrors arranged so that they are 90 degrees from each other). He pretended to understand and memorized: "90 degrees".
P.S. It's also the boiling point of water at standard pressure.

[stuart.reynoldsuk @ Jul 20th 2009 12:11PM]

The lead picture on the engadget front page is an art installation outside of the the "Play House" theatre in Nottingham City Centre (UK). Quite weird to see on the front page of an international tech site!!

Stuart

Nottingham!

[Zach @ Jul 20th 2009 12:28PM]

Maybe I'm confused, but if it only reflected where the light came from, wouldn't you only see the light source when you looked in the mirror? Since my eyes don't tend to create light, I wouldn't see myself.

[CityZen @ Jul 20th 2009 1:29PM]

Well, your eyes still reflect light, like most objects.

Although the only light you can see is that which enters your pupils, so therefore only the light that reflects from your pupils is what you'd be able to see in the mirror. Of course people's pupils are dark (because the pupil is the hole into which light enters your eyeball), so the only light that reflects is either that reflecting off the cornea or the light reflecting off the retina.

Yeah, the mirror would look pretty black, for the most part.

[froohoo @ Jul 20th 2009 6:23PM]

I thought corner cubes already did this... maybe this does it in some new more interesting way.