# How to calculate the amount of lunar regolith needed to reduce solar radiation in an area on earth by 0.2% or 0.5%

I am working on a climate change that doubles as a lunar infrastructure project. I am wondering if anyone could direct me to resources or help me answer the question of how much regolith scattered over an area in space would be needed to reduce the amount of solar radiation that reaches the earth in a targeted area. I know light diffusion makes this a bit awkward because of light diffusion. Still, any help would be appreciated. The ground area that would need to be shaded should assume to be 4 square miles and the speed of the regolith traveling through space would be ~0.5-1 km/second. This isn’t exactly accurate as orbital mechanics should allow for special trajectories that will exist at an angle instead of perpendicular to the direction light travels to hit the earth. There will also be periods of time where the clouds of regolith are traveling slower. But having a basis to make very rough calculations is what I need to progress. The distance the regolith will be from the earth would be 175,000 miles - 280,000 miles.

For those wondering why 0.2% of solar radiation matters, it doesn’t. That is too small of an amount to make a difference on its own. However, the effect could be stacked over targeted areas. The goal is not to reduce earth temperatures significantly on its own but mitigate the effects of climate change by reducing ice melt and increasing ice and snow expansion and/or to create a fog to further increase reflectivity. There will likely be other benefits as well but those are the ideas that have some scientific backing at the moment.

• Seems like this might be a bit of a stretch for space exploration? Might have more luck with astronomy or physics. – Starfish Prime Jan 2 '20 at 11:01
• If you don't find a suitable orbit around Earth to shade a certain area the project is impossible anyway. – Uwe Jan 2 '20 at 11:34
• SevenEves by N.Stephenson provides a reason you really REALLY don't want to try this. – Carl Witthoft Jan 2 '20 at 20:54
• @Uwe, the goal is not a stable orbit. Solar winds would push anything a little bit over time degrading the orbit meaning it would need to be constantly adjusted. The project would recollect the regolith back on the moon where the cloud of regolith and moon intersect. – T.A. McKay Jan 3 '20 at 6:05
• How to shade a targeted area only and continously during each day? – Uwe Jan 6 '20 at 18:57