Saturday, March 20, 2021 (Spring 2021 arrives at noon)
Today is spring equinox, which officially introduces a summer season. At noon, the earth’s orbit will be at the point where sun shines directly above the Equator. At that moment across the globe, the sun’s position creates nearly equal daytime and nighttime periods.
The line of shadow, known as a “straight terminator”, exists only at equinoxes. Otherwise, it’s continually shifting because of the earth’s tilt, 23.5 degrees, on its axis. Without the tilt, earth’s shadow line (or straight terminator) always would be straight-up-and-down, there’d be no seasons.
Earth’s tilt and continuous shifting create the seasons. For example, at noon today, the Northern Hemisphere will tilt directly toward the sun’s rays, a position that lengthens days and makes them warmer. By September, the Northern Hemisphere gradually will have shifted toward a fall equinox, when earth leans away from the sun, receives less daylight, and winter approaches.
Astronomy is a fascinating topic, especially today with much happening (or about to) in space, a world of increasing importance that too few understand. Our growing worries, about earth’s changing climate, food supply issues, and sociological shifts, point us toward potential new opportunities in space.
Already, science has produced worlds of knowledge in astronomy–about earth itself and its relation to outer space. While struggling to understand a future relative to the larger universe, we can absorb what’s already known scientifically. The history of how humans acquired our current knowledge fascinates nearly as much as possible paths forward.
Dear Friends: We must understand our old world, to tackle successfully a brave new one. Diana