Let's assume that there is one laser pointer for every 10 people alive (it's late, and there's nobody else here, so I can assume what the hell I like).

That's about 0.6 billion laser pointers.

Now let's assume that we can, by means of a website and some cunningly viral advertising, persuade one in ten of those belasered people to point their laser pointer at a particular point on the moon, at a particular point in time. We'll also assume that most laser- pointer-owners live in the western hemisphere, which will simplify things hugely

The website will, of course, display high-resolution maps of the moon, marked with a BIG cross.

So, that gives us 0.06 billion laser pointers.

A typical laser pointer is about a milliwatt of lase, so that equates to about 6000 Watts of lase, all pointing to the same bit of moon, give or take quite a bit.

I reckon that would be visible to the naked eye from Earth.

I've just thought of 8 reasons why this might not work, but sadly this margin is too small to contain them.
-- MaxwellBuchanan, Dec 26 2010

Lunar reflector http://www.universe...-are-getting-older/
Only one photon in every 10^17 is detected [mitxela, Dec 26 2010]

Baked in 2001: "Paint the Moon" http://www.afinelin...projects/paint.html
Aim millions of laser pointers to make a spot on the moon. [AntiQuark, Dec 26 2010]

While I would never stand in the way of a good assumption, I think that the typical advertised range of a 1mw laser pointer is in the range of a couple of miles and I think that the Moon orbits at a distance of sometihing like 250 miles...
-- Jinbish, Dec 26 2010


I think you're going to need more lasers, or an easier target.

Even when aiming a laser at the corner cube reflector on the moon, nothing is visible to the naked eye...
-- mitxela, Dec 26 2010


// The website will, of course, display high-resolution maps of the moon, marked with a BIG cross. //

Erm, high-resolution maps aren't going to be needed. A laser-pointer spot is going to be a large fraction of the size of the moon by the time it gets there, and most people cannot aim for squat, especially if they can't see the beam.

You also have the problem that any time the moon is usefully visible--high in the night sky--it is fully illuminated by sunlight. You can aim for the dark part of a new moon, maybe, but your participants are going to be limited to a time zone or so. A half moon is better, but it's going to be blinding to look at compared to a little laser illumiation over in the dark half.

But it woulld be beautiful to see this work.

// I've just thought of 8 reasons why this might not work, but sadly this margin is too small to contain them. //

Classic. Bravo, sir.
-- baconbrain, Dec 26 2010


Interesting lynx. I'd wager that more laser capability is available since that artistic experiment was tried back in '01 - we should try this again if only for the fun.
-- normzone, Dec 26 2010


Amateur astronomers sometimes own fairly-powerful lasers as sky pointers. They also often own sturdy tripods with optical mounts (for the lasers), and tracking motors, sometimes with software to aim the scopes at a particular spot in the sky. Amateur astronomers as your flash mob might be ideal.

I've just thought of 8 reasons why this would work, but sadly this annotation is too small to contain them.
-- baconbrain, Dec 26 2010


Well, ye gods and little fishes! Who'd've thought - baked, utterly, according to [AntiQuark]'s link.

I hereby say [marked-for-deletion] redundant.
-- MaxwellBuchanan, Dec 26 2010


a typical laser fired from Earth would diverge to cover a patch 400 kilometers in diameter on the moon. This is too diffuse to be of any use, but I think you can use a telescope to concentrate the laser beam.

I seem to remember that the smallest feature on the moon that a telescope could resolve is about 100 metres. So if you fired a laser through a telescope might be able to illuminate a 100 metre diameter patch on the moon.

If you wanted a nice bright spot, you would need to illuminate with the equivalent of the sun (i.e. 1.5kW per square meter), so about 12 million watts to cover the 100 metre patch.

You can get lasers that run at 1kW of continuously. So 12 thousand of these bad boys with 12 thousand suitably powerful telescopes and you could have a spot on the moon (or you could economize and fire several lasers though the same telescope).
-- xaviergisz, Dec 26 2010


I don't think you'd need to illuminate at solar brightness (although, as pointed out, you'd have to aim for an unilluminated part of the lunar disc, and probably when there's the barest crescent moon).

Given the logarithmic response of the human eye, I suspect an illuminate of 1/100th or 1/1000th solar would might be sufficient. This gives us 12kW, or 12 million good laser pointers.
-- MaxwellBuchanan, Dec 26 2010


Be very careful doing this! You might blind the pilot of a passing UFO, and cause a serious accident.
-- Wrongfellow, Dec 26 2010


Oi - I've got sheep grazing up there, and don't want them frightened with pesky lasers (Long-life Reflecting Moon Sheep)
-- xenzag, Dec 26 2010



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