Enlarge the Moon

Let's face it, the moon just isn't as impressively large in the sky as we want it to be. Even though we've got the biggest apparent-sized moon of any planet, we keep picturing it bigger. So let's make it bigger.

Or rather, let's have robots make the moon bigger, by digging rock out of the interior of the moon, and using that rock to build giant arched structures upward, layer upon layer.

We start by sending some robotic mining rovers up there, either solar- or atom-powered, with replication equipment. At first, we have folks control the robots from Earth---there's not much lightspeed delay, but it's going to get boring (and tunnelling (heh))--- so we add increasing autonomy as time passes.

The work begins with some of the robots tunnelling into the moon and bringing up the rock from the tunnels to the surface. The rock brought up is shaped by the construction robots into arched structures that build higher and higher, layer after layer, like multi- storied cathedrals. The lesser gravity of the moon will allow very light structures.

The interesting work, for this project, is that the tunnels reduce the density of the moon, decreasing the surface gravity, and the structures built on the surface increases its diameter, enlarging it, and further decreasing the surface gravity. Which allows even further expansion, as long as the robots keep rebuilding.

The robots don't need to stick to building with rock, of course. There's plenty of metals and other raw materials to be mined and processed into building beams and mining supports and robot parts.

Some of the robotic equipment uses the mined materials to build more robots and more robot-building machines. We could take measures to prevent them from replicating through space and taking over the Earth.

The robots constructing new surface layers can brighten the surface of the moon, by placing lighter-colored materials on top (the Moon is currently as dark as charcoal). That will brighten our nights a bit, and let more people notice the moon in the daytime. (The robots can, of course, arrange some dark materials into a sponsor's logo.)

As the building materials change, the diameter can further increase, which will allow even lighter construction. The very lightest materials now made are aerogels. The lightest structures now made are bubble/domes supported by gas pressure from inside. A stiff aerogel shell could be made gastight, and could insulate a hot gas inside it, and the moon could become a balloon.

The practical limit to the diameter of the reconstructed moon would probably be reached when the surface reached the balance point between the moon's own gravity and that of the Earth. Anything on the surface at that point could simply float away into space, which would be handy for shipping. Before that, electromagnetic launchers could be build into the tunnels and structures.

One useful shape to make from the moon converted into advanced materials would be a giant movie [TV or monitor type] screen to be seen from Earth. The shape for that would be reminiscent of the Eiffel tower standing on a plate. The flat bottom of the plate would face the Earth, with the tower pointing away, holding up enough mass to keep the structure stable through tidal lock. The [TV] screen could hold a [whole bunch of] projector [pixels] built from an array of lasers --- the robots should be told to not build lasers capable of destroying Earth. (According to my best math, the movie screen would be a little closer to Earth than the moon is now, and somewhat larger.)

Once the construction is finished, the robots could be asked to disassemble themselves for parts for other machines, or just allowed to roam the revamped moon, bored, frustrated, powerful and self-replicating, with lasers.