Home >> Science & Nature >> Astronomy

Why Is the Moon Closer?

At an average distance of 238,000 miles away from the Earth sits an object of roughly 2,000 miles in diameter that we are all familiar with -- the moon. Much like how the earth spins and rotates around the sun, the moon also spins rapidly and rotates about the earth. When gazing into the night sky, sometimes the moon might appear to seem bigger than other times. Although at times, based on climate and landscape, this is just an optical illusion, because of this rotation cycle there are times when the moon is in fact closer to Earth.

Phases
- The change we are most used to witnessing in the moon's cycle is its change from crescent, half, and three-quarter moons to full moon, which appears much larger in size, though it is not closer in distance. As the moon rotates around the earth, it changes with respect to the sun as well. The sun's light will cause a day and night side on the moon, much like on Earth. When we experience a full moon, the moon, Earth and sun form a straight line, with the moon being on the end. The vantage point from Earth will be that of the complete day-time of the moon, causing it to grow in the sky as a bright, large circle.
Perigee
- As the moon rotates about Earth, it does so in a slightly elliptical pattern. The ends of the ellipse are called the perigee and apogee. Its perigee is the end when it is nearest to Earth. On March 19th, 2011, a moon that was roughly 14% larger than normal full moons appeared in the night sky. The largest since 1993, this full moon took place just an hour before the closest point in the moon's perigee, making it literally just over 31,000 miles closer to Earth than the average full moon.
Illusion
- There are other times when though the moon is not in fact closer to Earth, a relatively common, if unexplainable, illusion will take place that makes the moon appear to be closer. If you gaze on any given night at a full moon while it's near the earth's horizon and then later gaze at it while it's in the night sky, it will appear to have shrunken. The phenomenon has been written about since ancient times; however, what is clear is that the moon doesn't actually change size. Instead, an optical illusion is occurring with the eye. One common theory states that the eye naturally makes the horizontal moon look larger as it "thinks" it's closer than what it is, because it is on the horizon.
Disappearance
- The moon doesn't only grow, it may also disappear during the months. The "new moon" is a part of the moon's rotation where it forms a straight line with the earth and sun; however, rather than lining up at the end, it lines up between the earth and sun. This causes the vantage point from the earth to only view the night-time side of the moon, meaning that the viewable part is dark and can also be seen only by looking in the direction of the sun. But even though the moon is out of sight, this doesn't mean that it's any farther away.

Astronomy