The Lagrange Sunshade: Its Effectiveness in Combating Global Warming and Its Application to Earth Defense from Asteroid Impacts, Beaming Solar Energy for Terrestrial Use, Propelling Interstellar Migration by Laser-Photon Sails and Its Technosigniature

One suggested method to partially mitigate the effects of global warming is the construction of a ~2,000 km dimension sunshade at or near the Sun-Earth Lagrange-1 (L1) Point. Opaque and transparent sunshades have been suggested for this application. Mass estimates are presented for both as well as a discussion of station-keeping issues. If constructed, such a megastructure would have additional applications. These include beaming energy to divert or destroy Earth-threatening Near Earth Asteroids (NEAS), space-based solar-energy production for terrestrial use, and energy beaming to accelerate laser-photon propelled starships engaged in interstellar migrations. Global warming may be a filter that an emerging galactic civilization might have to overcome. As such, technosignatures of extra solar star-planet Lagrange sunshades might be detectable by extremely large telescopes. Larger Lagrange sunshades might also be constructed by a civilization inhabiting a planet circling an aging star since stellar luminosity increases with star age. Keywords: Lagrange Sunshade, Earth Defence, Space-Based Solar Energy, Interstellar Migration, Technosigniatures