I would like to know if it is possible to make an engraving or burning moon's surface by focusing high energy laser beam from earth?
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1$\begingroup$ This sounds like a wild hypothetical out of left field. Is there a basis for your question? If so, you may want to expand your post, or it may get closed for needing clarity. $\endgroup$– called2voyage ♦Feb 16, 2021 at 22:21
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$\begingroup$ I remember something (probably false) about Pizza Hut (or some other corporation) wanting to carve their logo into the Moon. Idk, but I think the idea is gross violation of cosmic proportions. I hope nothing like that is ever realized. $\endgroup$– BMFFeb 16, 2021 at 23:01
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1$\begingroup$ slightly related and pretty cool!: Was there once a semi-serious space-art project planning to use solar reflectors to put a spot of light on the crescent Moon? The problem with "Is it possible to..." questions is that it is often possible but only with an extreme amount of money, time and effort. Of course this is possible, but it might require to the GDP of a medium sized country and a few decades to build enough lasers to do it. $\endgroup$– uhohFeb 17, 2021 at 0:53
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1$\begingroup$ imdb.com/title/tt0813112 $\endgroup$– uhohFeb 17, 2021 at 3:10
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1$\begingroup$ @uhoh: That was the first thing I thought of when I saw the question title. $\endgroup$– Fred LarsonFeb 18, 2021 at 17:54
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2 Answers
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The answer is no. Too much power would be required. Even if the power was somehow available, sufficient power to have an effect on the Moon would heat Earth's atmosphere to such an extent that oxygen and nitrogen would react. Such atmospheric disturbance would interfere with the laser.
Even the worlds most powerful laser would have no noticeable effect.
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$\begingroup$ so technically one would need 4 YW to engrave on the moon, which is not possible with our current technology. Right? $\endgroup$– user0193Feb 18, 2021 at 16:02
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$\begingroup$ Right, many many orders of magnitude and is not possible with our current atmosphere either. $\endgroup$– SlartyFeb 18, 2021 at 19:29
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Rather than worry about cost, legality, etc. , let me try to discuss the physics of focussing any beam (regardless of power) on the Moon's surface.
The biggest problem is that of atmospheric turbulence destroying the wavefront. In essence, you need to do "reverse adaptive optics," measuring the atmosphere and bending the outgoing wavefront so that the atmospheric effects produce a clean wavefront as the beam exits the atmosphere. This is what the various military anti-missile laser programs (Airborne Laser, e.g.) dealt with.
Next, you need to look at the usual diffraction problem: what kind of beam waist /focus can you achieve at that distance, given a practical size transmission aperture? (Calculating this Airy Disc pattern is left as a homework problem :-) ) .
Now that you've done all that, if you really want power levels sufficient to vaporize or sinter moon dust/rock, you'll need to ensure the beam power density, $\frac{W}{m^2}$ , is low enough that you don't instigate atmospheric heating, which would distort your beam again.
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1$\begingroup$ @user2705196 The answer is 'How much money do you have?' $\endgroup$ Feb 17, 2021 at 14:42
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1$\begingroup$ Would all the money in the world be enough? $\endgroup$ Feb 17, 2021 at 15:07
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$\begingroup$ You'd think atmospheric heating is what you'd want. Hot air is less dense than cold air, so there'd be less air to stunt your laser. And with enough power you could get a column of super-hot atmosphere at near-vacuum, right? $\endgroup$– BMFFeb 17, 2021 at 17:29
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2$\begingroup$ @BMF it's not attenuation, it's the nonuniformity of densities that causes wavefront degradation. $\endgroup$ Feb 17, 2021 at 19:26