Friday's full moon will be the biggest and brightest of the year. According to NASA, the Moon will appear up to 14% bigger and 30% brighter than other full moons seen so far this year. The reason? The Moon's elliptical orbit causes its distance from Earth to vary. Tonight's full moon will be only 221,560 miles from our planet, the closest it has been in the last 15 years. More from National Geographic.