Johannes Kepler explained the phenomenon 400 years ago. The Moon's orbit around Earth is not a circle; it is an ellipse, with one side 50,000 km closer to Earth than the other. Astronomers call the point of closest approach "perigee," and that is where the Moon will be Friday night:
IT'S MARS! In a coincidence of celestial proportions, the Moon and Mars are having close encounters with Earth at the same time. Moreover, the two will spend Friday night gliding across the sky side-by-side. It's a must-see event: sky map.
