bicycles, lunar lasers and cube corner retroreflectors

bicycles, lunar lasers and cube corner retroreflectors 0

I have a laser. A pretty powerful one so much so that I think it really would cause damage if it was aimed at my retina for a few seconds. It’s a green laser that I have used to aim at stars. You can see the beam at night time which makes it easy to follow compared to a finger or the cheap powerpoint lasers that people use in meetings.

I’ve aimed it at street signs too and what a powerful reflection I got. Almost blinding light. And probably not a good idea to do that…much. So would an ordinary red pointer laser do that? Probably. Maybe you wouldn’t get quite as bright a reflection but I’m sure it would be pretty bright. The laser that’s used at the Apache Point Observatory APOLLO project beams a laser to the moon….off a street sign there. No, it’s not a street sign. But dang, it works like a street sign. And it works like a bicycle reflector too.

All this reflective stuff comes from a neat little design called cube corner reflection. They can be made out of cheap plastic or prisms in glass or plastic and obviously can be in red color like the bicycle reflectors. The kind on street signs and on the very reflective tape have tiny beads that do this retroreflection. Some other designs can have coatings on the back to keep light from leaking out.

Here’s the simple explanation of why light is reflected. It’s not a flat or curved mirror because that would only work if you aimed it straight at the mirror to get the reflection. These little cube corners will take a light from a wide range of angles, bounce it off the inside corner of the cube back out at the exact same angle/direction that the beam came in. Meaning, you don’t have to be directly in front of the reflector for this to work. The angles inside the corner will take care of sending it back out to you.

So what if I aimed my green laser at the moon. Could I get a reflection off one of those retroreflectors the astronauts put there? No. The laser at the Apache Point Observatory is quite a bit more powerful, like gigawatts. My laser is 50 milliwatts I think. And the detector back at the observatory might only get one photon back. Our eyes wouldn’t even know one photon from another from looking at the moon.

If you bounce a small rubber ball into a corner, you should get the ball back at basically the same position that you threw it. Of course, how hard and what kind of ball and the fact it’s not a light beam won’t be exactly the same thing.

So for those bicycle riders that are now disappearing in the dark because the sun’s going down early, check those reflectors. You could also put some extra reflector tape on you and your bike. Here’s a website where you can get some…

Info about the APOLLO project:

APOLLO laser

APOLLO laser

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Do you want blue eyes?

Do you want blue eyes? 0

I’ve written about why blue eyes are blue. It has to do with the smaller amount of pigment in the iris and the Tyndall Effect. Pigment is not blue. It’s brown or yellow. And there are all kinds of color contact lenses that can change eye color and those are pretty easy solutions. Sometimes those color contact lenses can look pretty realistic.

But there are a few other ways and specifically I’m going to mention a way to change your eye color surgically using a laser. It’s not approved yet but if it does get approved this might be a huge thing! The company trying to get approved is called Stroma Medical Corp. They say that their laser can remove the outer layer of pigment cells and leave the rest of the iris alone. That I guess would then allow the Tyndall Effect to occur since the front layer of pigment would no longer absorb light rays.

Their website goes over a few of the concerns people have had with destructing pigment in the eye and the regulatory hurdles they need to get over before it’s approved. I admit, it sounds plausible and interesting. You might need about $5000 to do this and willing to only have 1 eye done at a time with a year wait before the other eye could be done. At least that’s how the procedure would work now.

They also say than they have a method that can predict what your eye color might look like before the procedure. Because there’s a mix of yellow and brown pigment and the amount of those can determine how much green there is in an eye, they must be saying that the results could be slightly different than what you might be expecting. They’ll have to sell some of you to believe a hazel colored eye is just as good as a blue eye. Maybe that’s true. Remember my post about that Afghan girl and her eye color?

Here’s the website below for that company. What I’m going to do is put a google alert on this company so if google gets any news on this I’ll put something in the comment section.

Just a note….I’m not implying that blue eyes are all that. It’s just interesting how we get blue color from our eyes and now this company wants to give brown-eyed people blue eyes while taking your $5000. Would it be worth it?


heterochromia, part brown, part blue



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