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FrozenGate by Avery

Paint the Moon???

C

cyclonite

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did anyone participate in this crazy idea last time??

Paint the Moon

given the fact that our moon wasn't obliterated I'm guessing noone from LPF joined the effort?? lol!
 





If you shoot the mirrors on the moon with a (pulsed) multiple kW laser and optics worth an arm and a leg you only get about 30-50 photons back.
:P

game
 
No way it would work, especially not with the "inexspensive yet surprisingly powerful" red lasers.
 
Extremely. Ideally if space was a clean vacuum, the laser beam would travel forever. However it's not (space junk, our atmosphere etc) so our lasers would barely make it to the moon, let alone back :P

On Mythbusters they fired a multi kW laser at the moon, and as GJ said, they only got a few photons back, even when it was bouncing off a reflector up there!
 
Yeah Neil Amstrong and Buzz Aldrin left a few mirrors on the surface during Apollo 11. Today scientists bounce lasers off them to measure the distance between the moon and earth however in practice it's extremely hard to do. They spend ages trying to hit the mirrors with very expensive optics and only get real measurements once in a while.

Anyway in order for the red dot to be visible, the reflection needs to be brighter than the reflection of the sun on the moon's surface. The sun on the moon's surface is much brighter than on earth because the moon has no atmosphere.
 
Even as a big group attempt it would be very difficult to produce a visible result.

The dot need not be brighter than the suns reflection: you'd attempt a thing like this on the dark side of the moon, ideally in a new-moon night so that you dont get blinded by the lit side.

In theory, it would work provided you used enough lasers... even if you hit just the surface and it scatters off randomly from there (not using the retroreflectors). The question remains: how many lasers would it take?

Sigar-box math:

- it would take at least several watt/m2 over a large area to be visible on the new moon.

- 1 mrad divergence laser, would light a circular area with 400 km diameter (!), which is a good portion of the size of the lunar surface facing us (its diameter is ca 3500 km).

- a 400 km diameter circle has a surface of 125.000 km2, or 125 billion m2.

- to light this area up with 10 w/m2, it would take 125 trillion watts of laser power

- 625 trillion dilda's would make it possible, provided every person on earth would be able to point 100.000 dilda's at the same area of the moon simultaniously.

Sigar-box conclusion:

It will not work unless we invest all of the earths resources into producing dilda's and batteries, and breed a lot more people to point them ;p
 
wow very helpful explanation and math there. thanks. there was a mention at one point of Google's interest in using lasers to advertise on the moon. not sure if it was a hoax but if it wasn't, it probably wasn't feasible either.
 
@ Benm: Then just DIY 200 trillion watts scanner and use it, right ? (j/k :D)
 
Hmm.. i do wonder how many digits fit on the power bill, but somehow i dont want to find out ;)

As for advertising in space: The moon would not be very practical. One could launch a slightly diffusing retroreflective (like traffic signs) sheet into low orbit, and laser paint onto that. At a distance of just a few 100 km, this would be entirely feasible in terms of being visible using existing, available laser technology.

The downside is that the sheet would have to be rather large to display a legible message. If you put it at 300 km orbit (similar to ISS), it would have to be a few km in size to appear the same size as the moon. I suppose a 5x25 km sheet would be large enough to display a few words on that you could read from the ground.

Still it will not work by aiming a few dilda's at it, but i suppose you'd have a fair chance using a 40W DPSS illuminator with a telescope-sized beam expander behind it. The majority of costs here would be launching the sheet, not the laser and optics to write in the sky ;)
 
Artificial clouds made using refractive fluids (or mixed with fluoresceine, for fluo effects :D) can work too ..... there's only one problem, with them ..... when these clouds filled of chemicals rain down, someone can hate you :P

Natural clouds, if compacts, are better :D
 
Benm: There's too much atmospheric drag at 100km. If we place a sheet in LEO at 300km, the sheet would orbit the earth at 25,000km/hour like the ISS. At that speed the real challenge would be tracking it with the laser :)
 
Oh, there would be huge problems with its practical application - such a sheet would sweep over in brief periods, and shoot across the sky to both observer and the laser tracking it... but these things can be done with current technology.

To get a fixed point in the sky, it would have to be geostationary, increasing the distance to 36.000 km. Even with retroreflective coatings, the thing would have to be huge (100x100s of kilometers), and it would take a lot more power and focussing to work with. The cost of all this would be insane.

So, laser message on LEO bilboard: feasible, in GEO not affordable, on the moon, not possible ;)
 
There are just so many factors that go against you, which make this project impossible.
 
Crazy folks, but it actually would work the other way around, if all the green lasers on the PLANET WERE ON THE MOON, AND POINTED AT YOU! LOL! -GH
 
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