Two Moons Away

Tonight at approximately 10:30 pm EDT, the Moon passes between the Sun and the Earth. No eclipse though — the alignment isn’t quite right, and so instead it’s just a boring New Moon. New Moons are boring because the side facing us isn’t illuminated by the Sun, and so the Moon looks dark. There’s literally nothing to see.

The Moon orbits the Earth while the Earth orbits the Sun, so a New Moon occurs once per orbit, or about once every 29.5 days (hence the term “month”). If the Moon’s orbit around the Earth and the Earth’s orbit around the Sun were perfectly aligned, then every New Moon would result in an eclipse of the Sun. But the Moon’s orbit is tilted by about 5 degrees. This means that the Moon sometimes passes above the line between Earth and Sun, and sometimes below that line.

Only when the Moon passes directly between the Earth and Sun does a solar eclipse occur. Both tonight, and in 29.5 days (on July 23rd), the Moon passes just below that line, and so no eclipse occurs. However, the following new moon, on 21 August, will be perfectly positioned and just for a few moments, viewed from just the right places on our planet, the Moon will block out the Sun, producing a solar eclipse.

We’re “two moons away” from eclipse day. Lots to do before then.

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