in the Venusian atmosphere. If made from carbon nanotubes or graphene (a sheet-like carbon allotrope), then the major structural materials can be produced The terraforming of Venus is the hypothetical planetary engineering procedure that would transform Venus from a planet hostile to life to one that could sustainably host humans and other lifeforms free of protection or mediation. Necessary adjustments to the existing environment of Venus to support human life would require changes including the reduction of the planet's surface temperature of 737 Venus could also be cooled by placing reflectors in the atmosphere. Reflective balloons floating in the upper atmosphere could create shade. The number and/or size of the balloons would necessarily be great. Geoffrey A. Landis has suggested that if enough floating cities were built, they could form a solar shield around the planet, and could simultaneously be used to process the atmosphere into a more desirable form, thus combining the solar shield theory and the atmospheric processing theory with a scalable technology that would immediately provide living space in the Venusian atmosphere. If made from carbon nanotubes or graphene (a sheet-like carbon allotrope), then the major structural materials can be produced using carbon dioxide gathered in situ from the atmosphere. The recently synthesised amorphous carbonia might prove a useful structural material if it can be quenched to Standard Temperature and Pressure (STP) conditions, perhaps in a mixture with regular silica glass. According to Birch's analysis, such colonies and materials would provide an immediate economic return from colonizing Venus, funding further terraforming efforts. Increasing the planet's albedo by deploying light-colored or reflective material on the surface (or at any level below the cloud tops) would not be useful, because the Venerian surface is already completely enshrouded by clouds, and almost no sunlight reaches the surface. Thus, it would be unlikely to be able to reflect more light than Venus's already-reflective clouds, with Bond albedo of 0.77.