Target for a Lunar Telescope

If at some future time an infrared telescope is placed on Luna, it might be located at 85 degrees either north or south latitude. It should be at the point that is furthest from Earth at that latitude. At such a spot the sun is never more than 6.5 degrees above the horizon as it shines from the direction of the equator, and Earth's disk only partially peeks over the pole once a month. So, it would require only a low wall to prevent these sources from interfering with the telescope.

Targets for a Lunar Telescope

• A potential target would be a Dyson sphere. This is the hypothetical effect of an advanced civilization capturing all of the radiant energy of its star and reradiating it in the infrared after using the energy. Some people have misrepresented this concept as a rotating solid sphere held up by a combination of centrifugal and rigid body forces, but Freeman Dyson himself referred to a swarm of objects which would orbit a star each in an independent orbit and each capturing the stars energy when it is not shaded by another object in the swarm.
• An alternative for the rigid body shell is to have a nonrotating shell held up by rails that move through tubular vacuum chambers in the rigid shell to circle the star at superorbital speed. These tubular vacuum chambers would be placed in numerous orbital planes. The shell would then be held up by magnetic attraction to the rails. If humanity were to become technically competent to build such a thing and for some reason driven to do it, building a shell at a distance of one astronomical unit from the sun, the shell would be held up against the six-ten-thousandths of a g that the sun exerts at that distance. Large areas of solar cells might be only a couple of millimeters thick while living spaces would include ten meter thick shielding and internal centrifuges to produce artificial gravity.
• Whenever one finds a silly idea attributed to a famous person such as Freeman Dyson, one should suspect that the idea may be a misrepresentation, and check exactly what the famous person said. And when people suggest that a rigid hollow sphere surrounding a star is impossible, only the lack of imagination is at fault.
• Some people might suggest, as was suggested for Larry Niven’s Ringworld, that a solid shell (or ring) around a star is dynamicly unstable. Larry Niven inserted station keeping thrusters into the Ringworld in his story. As an author he did not need to face the problem of refueling those thrusters. He could have specified a mass shifting scheme instead. Moving mass from the side of ring world too close to the star to the other side would have the ring closer to its unstable equilibrium position as a reaction, and direct gravitational force to moving the ring in the same direction. The same sort of mass shifting scheme would be easier in a nonrotating rigid sphere.
• Whatever means an advanced civilizations would use to gather all the energy of its star, if we do not find them doing that, the lack needs to be explained. One explanation, of course, is that humanity is the only industrial competent species in the galaxy.