Sunday, July 27, 2014

Tonight's Sky for July 27: Flat Ecliptic

The 25th was Old Moon, the 26th New Moon, which should make the 27th a Young Moon. Well, sort of because the Moon is technically Young today but it will be impossible to see from Earth thanks to the fact that the ecliptic plane is so low relative to planet Earth, which means that the 1% illuminated Moon will be setting less than 10 minutes after the Sun, and thus impossible to see. So, why does this happen?

Again, it all has to do with cosmic geometry, namely the Earth's 23 inclination relative to its axis. This is the same reason we have seasons. In summer, the Earth is tilted away from the ecliptic plane as seen from Earth and in winter, it is tilted towards the ecliptic.

As another interesting observation, the ecliptic and Sun are at opposite extremes in height at opposite times of year, too. 

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