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Author Topic: Can We Light Up The Moon From Earth ?  (Read 12404 times)

Offline neilep

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Can We Light Up The Moon From Earth ?
« on: 23/03/2008 00:10:40 »
Dear All,

See this moon ?



Nice eh ?...being delivered next Tuesday !!



Say one night the peeps of Earth got well and truly fed up with a crescent moon that night...What would it take to illuminate the moon to it's ' Full Moon' glory from here on   Earth !

Sat-a-light my education by illuminating this question for me .


thanks

neil






 

Offline turnipsock

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Can We Light Up The Moon From Earth ?
« Reply #1 on: 23/03/2008 00:33:06 »
I'm guessing we wouldn't make a lot of difference.

I still wonder about that Apollo experiment to measure the distance to the moon by bouncing a laser of some reflectors, every day. I think the Apollo missions may have compromised the moons oribit, so the distnace will change because of that.

What if the laser they fire at the moon misses the reflectors, wouldn't it cut a hole in the moon?

I have a built a big bonfire, when I light it I wonder if it can be seen from space?

I have cut down some trees recently
 

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Can We Light Up The Moon From Earth ?
« Reply #2 on: 23/03/2008 02:23:50 »
The moons surface area is about 6-7% of that of the Earth's.

The moon is approximately the same distance from the Sun as the Earth, so we can assume that the amount of light it is receiving is similar to that which the Earth receives (but without the interference from an atmosphere).  Thus, the amount of sunlight we receive from a full moon is achieved from about 6% of the light the Earth itself receives from the Sun.  Thus to illuminate the moon to the same extent, we would need to project, with 100% efficiency, as much light as we could collect with 100% efficient solar panels covering 6% of the Earth's surface facing the Sun (since, at present, solar panels are only about 15% efficient, ignoring cloud cover, that would mean you need to cover at least 40% of the side of the Earth facing the Sun with solar panels, and then at least double that to allow for cloud cover).  You would also need massive illuminators (lasers, or whatever) to project that light back up to the moon.

Maybe a more practical solution would be to launch some massive mirrors, that are of an area that represents a substantial fraction of the Earth's surface area, and have them reflect light that would otherwise have bypassed both the Moon and the Earth onto the surface of the Moon.
 

Offline DoctorBeaver

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Can We Light Up The Moon From Earth ?
« Reply #3 on: 23/03/2008 08:29:51 »
Maybe a more practical solution would be to launch some massive mirrors, that are of an area that represents a substantial fraction of the Earth's surface area, and have them reflect light that would otherwise have bypassed both the Moon and the Earth onto the surface of the Moon.

Why not just put a huge Chinese lantern in orbit?  With a picture of a beaver on it! :P

I read a sci-fi story years ago in which orbiting mirrors were used to direct sunlight at the Earth as it was in another ice-age. I seem to recall that Jerry Pournell of JPL had a hand in the science side of it.

In any case, if we were to put mirrors into orbit, rather than using them to illuminate the moon, wouldn't it be more practical to have the sunlight reflected at solar panels on the Earth to help with the energy problem?
 

Offline lightarrow

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Can We Light Up The Moon From Earth ?
« Reply #4 on: 23/03/2008 14:20:57 »
Maybe an even better idea would be to cover the Moon's surface with aluminum foil (or similar reflective materials/devices); the Moon's reflectance would increase a lot, don't know exactly how much, but I'm confident we would have almost daylight on Earth.
 

Offline DoctorBeaver

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Can We Light Up The Moon From Earth ?
« Reply #5 on: 23/03/2008 17:27:52 »
Maybe an even better idea would be to cover the Moon's surface with aluminum foil (or similar reflective materials/devices); the Moon's reflectance would increase a lot, don't know exactly how much, but I'm confident we would have almost daylight on Earth.

Vampires wouldn't like that.
 

Offline that mad man

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Can We Light Up The Moon From Earth ?
« Reply #6 on: 23/03/2008 17:49:23 »
The only problem I can see is if you have more sunlight illuminating the Earth then the CO2 produced would increase accordingly.

Less sunlight would be better.

The Russians once had an attempt at a space reflector that could produce a beam around 3 miles in diameter, not bright sunlight but more twilight. Unfortunately it didn't deploy after take off and was not tried again.

 

Offline Make it Lady

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Can We Light Up The Moon From Earth ?
« Reply #7 on: 23/03/2008 19:33:19 »
I think the mirrors should point at me and then you can bask in my radiance!
 

Offline lightarrow

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Can We Light Up The Moon From Earth ?
« Reply #8 on: 23/03/2008 20:05:00 »
Maybe an even better idea would be to cover the Moon's surface with aluminum foil (or similar reflective materials/devices); the Moon's reflectance would increase a lot, don't know exactly how much, but I'm confident we would have almost daylight on Earth.

Vampires wouldn't like that.
But werevolves would  :)
 

Offline lightarrow

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Can We Light Up The Moon From Earth ?
« Reply #9 on: 23/03/2008 20:12:46 »
I think the mirrors should point at me and then you can bask in my radiance!
mirror, mirror...who is the beautiest of the realm?
 

Offline lightarrow

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Can We Light Up The Moon From Earth ?
« Reply #10 on: 23/03/2008 20:21:59 »
The only problem I can see is if you have more sunlight illuminating the Earth then the CO2 produced would increase accordingly.

Less sunlight would be better.
Ok, then we could cover just a small fraction of the Moon's surface with mirrors which have a negligible reflectance on the red and infrared (the red-InfraRed would be absorbed instead of reflected, the mirror would heat up for this reason, the IR radiation generated from the increased temperature would be emitted in all 2π steradians, instead of towards Earth only); then we would almost only have bluish visible light coming here on Earth and the increase of photosinthesis process would be greater than the increase of greenhouse effect, so CO2 would be reduced.
Problem solved.
Do you have any other serious problem for humankind survival that you have to solve?  :)
« Last Edit: 25/03/2008 12:02:00 by lightarrow »
 

Offline that mad man

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Can We Light Up The Moon From Earth ?
« Reply #11 on: 23/03/2008 21:14:23 »
Sounds good to me lightarrow, a neat way in getting rid of the IR.  :)

Do you know if the moon itself reflects IR or is that mainly absorbed?


I've just been reading about the quest to put mirrors in space to reflect some sunlight away from Earth.
The idea being that by creating a mirrored "Maunder Minimum" less sunlight striking Earth could reduce overall temperature and cause a reduction in greenhouse gasses.

Only need around 55000 100km mirrors!

Seems to be a serious proposition as well.

Just thought, if the Moon does absorb IR then they could beam the light to the Moon and we could use it that way.

 

Offline Pumblechook

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Can We Light Up The Moon From Earth ?
« Reply #12 on: 24/03/2008 00:24:21 »
Half surface area of about 1.8 x 10e13 sq metres.  Say 100 Watts per sq metre = 1.8 x 10e15 Watts of light reaching the Moon.  = 1.8 Million Gigawatts of light. 

Even with 100% efficiency that is far more than all the output of all the world's power stations.   

Best you could ever do to illumate a tiny fraction of the surface.
 

Offline Bored chemist

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Can We Light Up The Moon From Earth ?
« Reply #13 on: 24/03/2008 19:25:00 »
"The only problem I can see is if you have more sunlight illuminating the Earth then the CO2 produced would increase accordingly."
Why?
Plants use light to remove CO2 from the air.
An H bomb set off near the moon might well light it up well enough, but I don't see the point.
 

Offline that mad man

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Can We Light Up The Moon From Earth ?
« Reply #14 on: 24/03/2008 20:24:32 »
Yes you are right Bored Chemist, sorry about that. [:I]

I should have said that the Greenhouse effect would increase accordingly, not the CO2 produced.

 

Offline Bored chemist

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Can We Light Up The Moon From Earth ?
« Reply #15 on: 24/03/2008 21:01:40 »
"I should have said that the Greenhouse effect would increase "
why?
 

Offline lightarrow

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Can We Light Up The Moon From Earth ?
« Reply #16 on: 25/03/2008 11:58:38 »
"I should have said that the Greenhouse effect would increase "
why?


Because Earth would be heated up and this would increase water vaporization and so greenhouse effect (water vapour is one of the substances that would increase solar light's absorption and decrease Earth's red-infrared irradiance, since red and IR are absorbed by water vapour and cannot totally escape from Earth's surface).
 

Offline lightarrow

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Can We Light Up The Moon From Earth ?
« Reply #17 on: 25/03/2008 12:15:34 »
Sounds good to me lightarrow, a neat way in getting rid of the IR.  :)

Do you know if the moon itself reflects IR or is that mainly absorbed?

It's a good question! Considering that the surface is made of fine powder, I would say it's mostly absorbed, as much of visible light, and even more because powder (let's say is made of SiO2 tiny grains) reflects higher frequencies more than lower ones, according to the equation (valid for normal incidence):
r = [(n-1)/(n+1)]2
r = percent reflectance
n = refraction index
and you know that n increases with frequency.
Quote
I've just been reading about the quest to put mirrors in space to reflect some sunlight away from Earth.
The idea being that by creating a mirrored "Maunder Minimum" less sunlight striking Earth could reduce overall temperature and cause a reduction in greenhouse gasses.

Only need around 55000 100km mirrors!

Seems to be a serious proposition as well.

Just thought, if the Moon does absorb IR then they could beam the light to the Moon and we could use it that way.

Yes, however consider that Moon would, anyway, irradiate more IR than now because it would heat up and this would increase its IR irradiance.
 

Offline Bored chemist

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Can We Light Up The Moon From Earth ?
« Reply #18 on: 25/03/2008 19:16:30 »
One way in which silica is measured makes use of its strong absorbtions in the IR.
While the formula above is correct for non absorbing materials at normal incidence it runs into problems when looking at things like the moon.First it has a chemically complex nature so it probably has lots of absorbtion peaks. Secondly the structure of the material can make a big difference. If you get a pile of razor blades and look at the edges they seem almost black even though they are actually quite shiny; on the other hand coal is quite reflective (at near normal incidence) even though it's black.

The moon has a pretty poor reflectance for visible light and I guess it's not much better in the IR.
I see from the 'net that someone has looked at the problem, Moon: Near-Infrared Spectral Reflectance, A First Good Look, McCord, T.B., R.N. Clark, B.R. Hawke, L.A. McFadden, P.D. Owensby, C.M. Pieters and J.B. Adams, J. Geophys. Res., 86, 10883-10892, 1981.
or
 http://ntrs.nasa.gov/search.jsp?R=372697&id=1&qs=Ns%3DPublicationYear%257C0%26N%3D4294844028
 

Offline neilep

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Can We Light Up The Moon From Earth ?
« Reply #19 on: 27/03/2008 21:08:42 »
Can I just thank you all for a fascinating thread and all your wonderful contributions !!

THANK YOU !!
 

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Can We Light Up The Moon From Earth ?
« Reply #19 on: 27/03/2008 21:08:42 »

 

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