Expert: Steven LJ Russo - 3/6/2007

Question
hi,
My mom who lives in Indonesia said that the moon in Europe/USA during summer looks bigger than in Indonesia. Several friends of mine and I also have the same impression. So I wonder why? Is it because the distance between the moon and Equator is bigger during the summer in Northern Hemisphere? I had a debate about this with a friend of mine who happen to be an Engineer, and he said it's not true that the moon looks bigger in Europe. Could you enlighten us? Thank you for your time.

Answer
WOW!!!!

I can probably write 5 pages on Moon size stuff, but I will try to keep it simple.

The Moon will NOT look bigger or smaller regardless of what country or continent you are on, however, the Moon will appear bigger or smaller in the sky depending on a number of things.

First off, the Moon will always look bigger on the horizon (and so will the constellations) during rising or setting due to something called the "Moon Illusion".  It is actually a "mind-eye" perception problem.  The moon will look smaller when higher up as this "mind-eye" problem "goes away" when objects are higher in the sky.

Secondly, as the Moon travels around the Earth near an imiginary line in the sky called the Ecliptic, it sometimes travels lower in the sky, and looks larger, and sometimes travels higher in the sky, and looks smaller.

Also, as the Moon travels around the Earth, it  is sometimes closer to us, and sometimes farther away.  This will make it look larger or smaller.

You can go to the following links for more of this:

http://science.nasa.gov/headlines/y2005/20jun_moonillusion.htm

http://www.fourmilab.ch/earthview/moon_ap_per.html

Steve

http://www.look-to-the-skies.com