The moon in the black sky

Dear Evil Engineer: Can I deface the moon with my crude artwork?

Image credit: Dreamstime

The month, the Evil Engineer considers the practicalities of graffitiing a willy on the moon for all to see.

Dear Evil Engineer,

I have a portfolio packed with chaotic antisocial acts, like shaving pet cats and urinating in public fountains. In the past year, I have made a name for myself in crude vandalism, having graffitied penises on walls, created phallic crop formations and even paid a skywriter to draw a penis in the sky for thousands to enjoy.

Next, I’d like to try drawing a penis on the Moon for the entire world to see. Is this possible?


A sophomoric villain


Dear villain,

What you are looking for when you create these obscene pieces of art? Perhaps you are seeking external validation, or trying to provoke a charged public reaction in order to fill a void within you? I advise you to consider psychoanalysis because 1) an analyst would have a lot of fun with you and 2) it is not feasible to draw something on the Moon that would be visible from Earth. Let me explain.

The obvious option is to project your phallic art onto the near side of the Moon. This would require an extremely bright light on account of the 384,000km between the Earth and Moon, and the lunar surface’s lack of reflectivity. Your best chance would be during new moon, so you are not competing with the Sun.

For simplicity’s sake, consider creating a spot of light on a Moonlike disc comparable to the illumination of sunlight on that spot: 100,000 lux. There is a simple equation to convert between E (luminous flux per unit area, measured in lux) and I (directional luminous intensity, measured in candela): I=Ez2, where z is separation between source and target. Plugging the Sun’s luminescence and the Earth-Moon separation into the equation gives you a beam of 1.4x1022 candela. Bearing in mind that about a quarter of visible light will be absorbed by the Earth’s atmosphere this will require a 1.9x1022 candela beam for each ‘pixel’ of the projected image.

The average person with 20/20 vision can resolve details of around one arcminute in size, so the Moon cannot be observed in much higher resolution than 40x40 pixels at best. A quick sketch in a grid shows that a line drawing of a penis and testicles covering most of the diameter of the Moon takes around 100 ‘pixels’: that is, 100 of these 1.9x1022 candela beams directed at the lunar surface.

The Luxor Sky Beam – the world’s strongest light beam – is 4.2x1010 candela and drains 315,000W. If you use similar xenon lamps, you are likely to require power at least comparable to total world power consumption (around 20TW).

You would probably get the sharpest, brightest result using lasers, which tend to diverge minimally; scientists working on the Lunar Laser Ranging experiment target lunar retroreflectors using lasers and can detect a faint returned signal, although they compare
this to shooting a moving dime from 3km away. Other difficulties include the fact that the Moon is not a disc, so the penis shape will become distorted and fainter at the edges unless you adjust for the 3D shape with projection mapping, and the non-zero background illumination of the night sky. It is unsurprising, then, that experts before yours truly have concluded that projecting onto the Moon is not a challenge worth pursuing; Coca-Cola’s marketing department reportedly spent a considerable sum exploring the idea of laser projection onto the Moon before concluding it was unfeasible.

If you have the means to reach the Moon, more options are available. You could try casting a shadow of a penis across the near side of the Moon; this would require you to construct a vast, 2D phallic structure and position it ‘atop’ the Moon at a tangent to its surface, such that when sunlight falls on the Moon at certain times, the shape is projected onto its near face. This would telescope pleasingly throughout the lunar cycle. However, the structure would need to be implausibly large: around 2,000 times taller than the Burj Khalifa. How would you support and construct such a large structure, let alone on the Moon? It is possible that carbon nanotube research will lead to the development of ultralight, ultrastrong materials which could make these megastructures more feasible, although this remains speculative for now.

There is also the possibility of digging markings into the Moon that would be visible from Earth. Remember that the Moon can be seen in roughly 40x40 resolution, and it takes around 100 ‘pixels’ to mark out a penis and testicles across the lunar surface: this is equivalent to an area larger than France (~750,000km2). Visible lunar craters are at least 2.5km deep – Kepler is 2.6km deep, for instance – so digging out tracks on the Moon will require you to shift around 2,000,000km3 of Moon rock. For comparison, Mount Everest has a volume of approximately 60km3. Your best bet may be to nuke the shape into the Moon, although given that the largest craters in the US and Russia ever created by nuclear weapons (Sedan and Chagan) are only around 0.1km deep, this will only get you so far.

You may be better off trying to cover parts of the Moon with reflective materials. The Moon is highly mottled and causes light to scatter; covering its surface with retroreflectors such that sunlight is cleanly reflected in the shape of a penis is still a mammoth task, but could be the most plausible way to achieve your goal. Even this, however, seems like a lot of effort for a villain who seems to find genuine enjoyment in petty crimes. There are easier ways to inflict your childish drawings on the entire world, such as hacking high-traffic websites and putting pictures on their homepages.

The Evil Engineer

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