Theres no Earth observing telescope parked in orbit. There are no geosynchronous elevators on which a camera can be mounted. The images that went into each of the remarkable city zooms come from data collected by a group of Earth imaging satellites. (NOTE: The video presentation on SPACE.com is only available on QuickTime and Real media players.)

And while not all of the zoom sequences use precisely the same series of data sets, most do. Plus, those including data from alternative sources employ techniques similar to the general case described here.From farthest away we see the Earth as a globe. This comes from data stitched together using information from MODIS, an instrument on Terra, NASA's flagship Earth-observing satellite.

This first picture has a resolution of 26,245 feet (8,000 meters). As our virtual camera begins its long fall to ground, we pass through a different kind of MODIS information; data in the second layer resolve details as small as 820 feet (250 meters) across. Our measure of detail has just improved dramatically.

Next we find our apparent speed increasing as the surface of Earth envelops our sense of horizon. The data supporting this perspective comes from the land imaging workhorse of NASAs fleet -- Landsat 7. These images resolve features 50 feet (15 meters) across.

Finally, as we rush in to the limits of Landsat 7s data capabilities, we move to our final slice of visual information. Taken by a remarkable commercial satellite called Ikonos, the world's first spy-quality Earth imaging satellite owned by a private company, features as small as 3 feet (1 meter) across come into view. Individual cars, trees and baseball diamonds appear like ghostly apparitions on the ground. In virtual space weve traveled far more than a thousand miles (1,610 kilometers)but in real terms, nothing besides electrons, photons and an elite group of computer and spacecraft personnel have moved to make these images possible.