Easiest way to write your name on the moon

It’s one of the great traditions, not of sci-fi but of fiction in general: if you want the world to know who’s really in charge, write your name on the moon. Actually, some famous moon-scholars from literary history have chosen to write other messages, but according to physics blog Canonical Momentum, the challenges are basically the same: if you want to leave a note on Luna, you’ll need some seriously impressive hardware.

The first and most important challenge will be planning the message itself. To be legible to the human eye on the ground (preferable, we’ll assume), the letters must be at least once arc-minute high, or we cannot distinguish between two points. This arc-minute size corresponds to roughly 100 kilometres, meaning that any detail smaller than that will smear together and produce an unreadable message. With a message like “Hello,” we end up with a final size roughly equivalent to that When it comes to actually creating the message, things get a bit more complicated. What do you use to make your mark? Nuclear weapons certainly have the fire-power, but they leave circular impact craters that are hard to use for drawing, and they certainly don’t stand out well against the rest of the moon’s surface. 

Craters are also quite small, and despite all the destructive power of a nuclear bomb, its mark will still be small when seen from roughly 375,000 kilometers away. Though shadows, or hordes of coordinated mini-nukes could be used cleverly enough, we’re unlikely to use nuclear pointillism to rough out a message on the moon.

Using a laser is much more likely. At an achievable power level — say, 10 megawatts — a laser fired at the moon could cover roughly three meters with enough energy to reach the melting point of moon dust. This will have created a portion of the lunar surface that remains visible through reflection — though the downside is that the mark is only three meters to a side. 

Firing this X-ray laser will require a huge fraction of the energy used by the US each year, but should work at slowly burning a message into the moon. The word “slow” is operative here, as something like a 50,000-year timeline becomes necessary when working with any existing laser technology.

Check out the full post for a much more detailed look at how this all might work. The ultimate point of this thought experiment is to illustrate how hard it would be to do something like write your name on the moon — thankfully, hard enough that it probably won’t happen until a man with a chair for a face becomes ambitious. Remember, though, the Moon is tidally locked to the Earth and thus shows us only one side; if someone did write their name on the Moon, we’d have to stare at it non-stop until the end of our planetary system.

Or, of course, until someone invented Lunar tattoo removal — and the real world doesn’t have a Tick to send to the Moon with bombs strapped to his back.