Deforestation: 1986 Detecting changes through time is one of the most powerful uses of remote sensing. These Landsat images, taken in 1975 (left) and 1986(right), disclose how many acres of forest lands were converted to agricultural use in the Brazilian state of Rondonia. The fishbone pattern of roads radiating from the major highway indicates the changes. NASA researchers have estimated that 9,000 square miles have been converted from forest to agriculture in this area of Brazil.

Supernova: 1987 Oscar Duhalde was outside taking a break from his telescope at the Las Campañas Observatory in northern Chile. In the southern sky he noticed a bright object he had never seen before near the Tarantula nebula. Halfway around the world in New Zealand, an amateur astronomer, Albert Jones, saw the same thing: a supernova, or exploding star. This was the first such event in our cosmic neighborhood in nearly 400 years! The star that exploded was a blue super giant; the light from it had been traveling for 160,000 years through space before reaching the Earth and the eyes of Duhalde, Jones, and other astronomers who saw it! Galileo just missed seeing it by a few hundred years!!