Has the Moon got bigger (or did you imagine it)?

[emad]

Has the Moon got bigger (or did you imagine it)?
By Steve Connor and Arifa Akbar
24 June 2005


One of the morenoted optical illusions in the annals of visual deception appeared in the night sky this week when a giant full moon appeared on the horizon.

The giant ball of yellow-white light made the Moon appear to linger for longer, and Earth's satellite seemed larger at that point in its journey across the sky than at any other position.

In fact, the size of the Moon in the sky does not vary and its apparent enlargement on the horizon is purely a trick of the eye. It was first written about by the ancient Chinese and Greeks - although scientists are still arguing over its cause.

The illusion was especially visible on Wednesday night because this month's full moon coincided with the summer solstice, while clear skies gave spectacular views as the moon rose slowly above the horizon.

http://news.independent.co.uk/world/science_technology/story.jsp?story=649234

SURE was big and spooky...........

[Puzzler]

1. Actually, to nit-pick...

"... the size of the Moon in the sky does not vary..."

It does, albeit slightly. The moon's orbit is elliptical, so it is slightly closer (perigee) to the earth twice each orbit, and slightly more distant (apogee) at other times. Its actual apparent diameter does vary... although not by a noticeable amount, but it is measurable.


-P

[Ready4Change]

2. Perspective.

I figured this out when I was a a crossing guard in elementary school. I'd get up and on my corner before dawn, and watch the sun rise. I wondered why it was so big.

Then I realized it only appeared big because I was comparing it's apparent to things I knew were big on the distant horizon. Trees, buildings, etc... Once it had risen above the horizon there was no longer anything to compare it's size to, except the sky itself, which makes everything look smaller.

See the sun rise in a forest, or from a valley, and it's much less impressive, because you can only see it in comparison with objects which are much closer than the horizon.

I seem to recall reading that, if anything, the rising sun (or moon) is smaller. Atmospheric lensing tends to flatten their vertical dimension, making them appear like ovals.

[BlueJazz]

3. To nitpick even further....The Moon appears actually......

..Smaller when it's on the horizen than when overhead.

When overhead you're about 3500 miles closer to it....