.ON APRIL 2ND a gizmo resembling a snow machine on the deck of the USS Hornet, an obsolete aircraft-carrier anchored in San Francisco Bay, began making a moisture of salted aerosol particles. The clinical cooperation behind the project, the Marine Cloud Whitening (MCB) program, led by the Educational institution of Washington, is actually looking into whether such aerosols might assist to decrease weather change through a kind of "geoengineering". What does this term mean-- and why is it so questionable?