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View Full Version : Lunar Graffitti and the Naked Eye on the Earth



Tuckerfan
2006-Feb-21, 08:08 AM
In The Man Who Sold the Moon Robert Heinlein discusses a plan to use carbon black to put a soft drink company's logo on the face of the Moon. While Heinlein describes how this could be accomplished, he doesn't really say (IIRC) how wide the lines would have to be so that they could be viewed with the naked eye of an Earth based observer. I assume that there's a fairly basic formula to figure this out. Anyone know?

grant hutchison
2006-Feb-21, 09:27 AM
Resolution of the human eye is around one arc-minute (that's the width of the lines making up the letters on the optician's chart at the 6:6 level [20:20 in the USA]). The Moon is 30 arcminutes across when seen from Earth, so at best you could fit in a pretty crude logo: something like a single character from an old dot-matrix printer, filling the whole disc.
Since the Moon is 3476km wide, the lines would have to be rather more than 100km wide in the centre of the lunar disc; wider at the edges.

Grant Hutchison

Fram
2006-Feb-21, 01:23 PM
Easy test: take the capsule of a bottle of your favourite soda, and keep it at such a distance that it just eclipses the full moon. Are you now able to "read" (i.e. recognize) the logo? (You may need to shine a light on it, obviously).
An easy logo (say, the T of Toyota or the swoosh of Nike) should be doable, while something more complicated would be unreadable. And of course, the whole logo is only visible a few days a month...

Launch window
2006-Feb-21, 01:49 PM
Pepsi have already put their adverts into LEO by using space stations
http://www.capcomespace.net/dossiers/espace_sovietique/mir/1996%20pepsi%20cola%20in%20space.gif
http://www.seds.org/spaceviews/9607/images2/pepsi.jpg

Fram they could overcome visibility problems by using massive Neon signs on the Moon, making some luminous ads but also some of the worst night-pollution ?
http://bigwhiteguy.com/photos/photo.php?imageID=793
http://www.neon-signage.com/
http://www.unicos.co.jp/kens/neon.html

grant hutchison
2006-Feb-21, 01:54 PM
Fram they could overcome visibility problems by using massive Neon signs on the Moon, making some luminous ads but also some of the worst night-pollution ?Same problem with resolution, despite the improved visibility. We're actually less good at separating light sources against a dark background than we are at separating dark lines against a pale background: most people are unable to distinguish binary stars that are only an arcminute apart. So your neon sign would have to be very simple indeed.

I guess this is an interesting corollary to the Moon Illusion: the Moon looks like it should be easily big enough to contain several lines of legible text, or a clear Coca Cola logo, but it isn't.

Grant Hutchison

Swift
2006-Feb-21, 02:08 PM
Fram they could overcome visibility problems by using massive Neon signs on the Moon, making some luminous ads but also some of the worst night-pollution ?
http://bigwhiteguy.com/photos/photo.php?imageID=793
http://www.neon-signage.com/
http://www.unicos.co.jp/kens/neon.html
Now there is an interesting idea, making a neon sign that had tubes 100 km wide and 100s of km long. You won't need the tube for the vacuum, as the moon is probably a good enough vacuum, but you would need to contain the neon at a high enough density. I suspect the power requirements would be pretty impressive too.

What about using a mixture of carbon black and some sort of fluorescent compound? When in daylight, the carbon black would be the visible material and the fluorescent material could absorb the light and get re-charged. In darkness the fluorescent material would glow (though I suspect it would not be particularly bright and probably wouldn't continue to glow for more than a few hours).

NEOWatcher
2006-Feb-21, 02:14 PM
Pepsi have already put their adverts into LEO by using space stations
But not visible to the naked eye from earth


Fram they could overcome visibility problems by using massive Neon signs on the Moon, making some luminous ads but also some of the worst night-pollution ?
I would be interested to know what a neon sign builder charges per foot (ballpark estimate will do).
Now lets see... 2160 mile diameter logo. Let's try Pepsi.
A ring around the logo, and 2 lines a little longer than the diameter.
2160 * pi + 2 (1.1 * 2160) or about 6 million feet of neon tube.
And that's not to mention all the other issues like how to power it, how to get it there or make it there, how bright will it have to be (Oh that one could be a killer on a full moon).

ngc3314
2006-Feb-21, 02:25 PM
But not visible to the naked eye from earth

I would be interested to know what a neon sign builder charges per foot (ballpark estimate will do).
Now lets see... 2160 mile diameter logo. Let's try Pepsi.
A ring around the logo, and 2 lines a little longer than the diameter.
2160 * pi + 2 (1.1 * 2160) or about 6 million feet of neon tube.
And that's not to mention all the other issues like how to power it, how to get it there or make it there, how bright will it have to be (Oh that one could be a killer on a full moon).

I had a chance to see the escaped tether from one shuttle mission while it was still it orbit. Spookiest thing I can remember seeing in the sky - a 1.5-degree, electric blue line (a wiggle at one end made it slightly like an exclamation point with binoculars). The further disturbing thought came to me of how many corporate logos could be made by linked or spinning tethers (thinking of, say, the Mercedes logo wheeling across the sky). Why so disturbing? I certainly don't want someone's advertising drifting across the field while I'm taking data. On the up side, tethers have lots of drag and re-enter quickly. (I think that mission was STS-75, but KSC seems to have broken their "history" web site again.)

NEOWatcher
2006-Feb-21, 02:31 PM
I had a chance to see the escaped tether from one shuttle mission while it was still it orbit. Snip
Alas; just another opportunity I missed seeing.

Just think, NASA had a hard time controlling just one straight line, now think of the engineering for a logo. I think we're safe for some time yet.

01101001
2006-Feb-21, 04:26 PM
Then there's the southern-hemisphere problem. What company wants their logo to appear upside-down to so many people?

For a reasonable fee, a corporation might obtain rights to something like:

http://www.01101001.com/temporary/nike_t.gif (http://www.01101001.com/temporary/nike.gif)

Sun Microsystems (http://www.sun.com/aboutsun/) is way ahead of the game, but that logo might look pretty disconcerting stamped on the moon.

umop ap!sdn
2006-Feb-21, 04:55 PM
In darkness the fluorescent material would glow (though I suspect it would not be particularly bright and probably wouldn't continue to glow for more than a few hours).
Most phosphorescent compounds have a glow with a half life measured in seconds. Considering how slowly the Moon rotates, even a few hours wouldn't do much. Now if the dark areas contained batteries charged by solar collectors and the light areas full of powerful lamps, it could work.

(Although an electric green edge around the Moon's dusk terminator line would look pretty nifty. :D)

Tuckerfan
2006-Feb-23, 07:03 AM
Okay, let's say that Mitsubishi decided they wanted to put lights on the Moon, which when lit, would suggest (though not necessarily be identical to) their logo. How big and how bright would those lights have to be?