If you thought this week's full Moon looked a bit small, you were right. It was the smallest full Moon of the year. 

Image credit: Anthony Ayiomamitis of Athens, Greece

The above image shows the largest full Moon of the year (Jan. 30) vs. the smallest (Aug. 25th). The difference between the two full moons is around 14.5% and certainly easily noticeable to the naked eye..

Johannes Kepler explained the difference 401 years ago: The Moon's orbit around Earth is an ellipse. One side of the orbit (perigee) is 31,068 miles closer to Earth than the other (apogee). The full Moon of Aug. 25th was a distant apogee Moon, and that's why it looked so small.