On Apr 2, 9:00 am, (Joseph Nebus) wrote:
Damon Hill writes:
Mike Ross wrote in
:
I thought I saw recently somewhere a plan to use a laser to put ads on
the moon. Is that really possible? Seems like the power levels
required would be prohibitive, or at least dangerous to anything
passing through the beam.

Should some group decide to such a thing, I wonder how hard it would
be to find the source of the laser?
Given the low albedo, the size of the area that'd need to be illuminated
and distance of the target...yeah. Serious power. Got to keep the
beam from spreading too much and the earth's atmosphere might tend to
scatter the beam a bit, too.
Even so, surely someone's tried this...?

An article for Nature that I dug up when this was discussed a
couple weeks back on rec.arts.sf.written claimed that the signal loss
on a laser bouncing from Earth, to the reflectors on the Moon, back to
the Earth, is something like 10^{-21} -- and remember, that's to the
spots on the moon designed to reflect as perfectly for the mass as
humans could manage, circa 1970. I'm sure I can find it again, but it
wasn't a particularly tricky Google search for it.

Considering that most of the Moon has a vastly lower albedo,
and that you would need to send up enough light that what's reflected
stands out against the full moon's intensity -- and to complicate
things, that the logo is a light green, which is harder to read on the
basically-white background than, say, red would be -- and ... I don't
have a quick way to calculate what power is needed, but feel safe to
say nobody's got a laser that'll do that.

--
Joseph Nebus
------------------------------------------------------------------------------

Then simply laser illuminate upon the physically dark moon as of
otherwise being earthshine dark, and otherwise by way of simply using
the moon's L1 as the efficient station-keeping location for those
laser cannons, and of easily creating every viable color you'd like
(including UV and IR if you'd like).
.. - Brad Guth