Vernal Equinox The Sun crosses the equator from south to north today. It's a moment known as the vernal equinox, and it marks the beginning of spring in the northern hemisphere. The first is the distorting effect of Earth's atmosphere. But Earth's atmosphere bends the Sun's image around the curvature of Earth, allowing us to see it a little early at sunrise, and a little late at sunset. sunrise occurs when the top of the Sun's disk peeks above the horizon, while sunset occurs when the Sun completely disappears below the horizon. the equinox -- which occurs, incidentally, at 6:33 a.m. Central Time. Script by Damond Benningfield, Copyright 2005
