Anonymous
Anonymous asked in Science & MathematicsAstronomy & Space · 1 decade ago

# Why does the moon looks huge sometimes, and sometimes it looks smaller?

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• Anonymous

The moon's orbit is elliptical and not a circle. Therefore there is a time every month when the moon is at its nearest to the earth (perigee) and a fortnight later when the moon is at its furthest away (apogee). 13 of each a year. The distance at every apogee will vary from lunar month to lunar month, as will the distance at every perigee.

Look at the photos in this link to compare the difference

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

The mean distance to the moon, 384401 km, is the semimajor axis of its elliptical orbit. The closest perigee in the years 1750 through 2125 was 356375 km on 4th January 1912; the most distant apogee in the same period will be 406720 km on 3rd February 2125

Here are the distances for the rest of the year.

Oct 17 perigee: 363,826 km

Nov 2 apogee: 405,722 km

Nov 14 perigee: 358,972 km

Nov 29 apogee: 406,479 km

Dec 12 perigee: 356,567 km

Dec 26 apogee: 406,600 km

So the answer to your question "why does the Moon look huge sometimes, and sometimes it looks smaller?" is that sometimes (perigees) it is nearer to us and that is what makes it look bigger and at other times (apogees) it is further away from us and that is what makes it look smaller.

Compare how large a football looks from the stands at a big football stadium with how large the same football looks from the touchline at a school playing field, where the spectator is closer to the game.

• 1 decade ago

Does it? Or is it that you see photos taken with a telephoto lens near the horizon with a tree, a house, or anything else you can relate to?

Because I have been sailing for many years and prior to the GPS I have been using sextants to find my position. The sun and the polar star is most used but sometimes the moon is also used. It takes a lot of calculations but when you're on the watch in the middle of the night, there is not much else to do.

Anyway, while there is a correction table for the semi-diameter of the sun and the moon according to the read elevation, this is minimal and not perceptive to the eye.

The moon may seem bigger when near the horizon but it is not. The moon and the sun both cover roughly half a degree of angle of view.

• 5 years ago

Yes it certainly does appear that way, however it is not. The visible moon size is relatively the same all night. What is different is your vantage point and whether or not any local objects are in view with the moon for comparison. Objects give the moon a seemingly larger look as opposed to when the moon is in the sky alone with no surroundings.

• Feythe
Lv 5

As "Gonashotmyse" correctly said, the moon LOOKS larger when it's near the horizon because our brain compares it to foreground objects like houses or trees.

But this is just an illusion. The moon is not really any larger.

Google the term "moon illusion" to find out more info, or check out this link:

http://www.usatoday.com/tech/science/space/2008-06...

• 1 decade ago

The moon goes through a cycle every 27 days. If you look up lunar calendar on Google it will give you the dates on when it is waning and waxing.

• 1 decade ago

the moon look's larger near the horizon because you have something to compare it to unlike when it's high up there is nothing to compare it to so it looks smaller.

• 1 decade ago

if you mean... why does the Moon look larger near the horizon... well, its an illusion.

its actually smaller.

you can verify that yourself, with hardly any effort.

• 1 decade ago

It looks larger when it is closer to the horizon because of magnification effects of the atmosphere.

• 1 decade ago

Complete optical illusion-- if you actually measure the diameter it is exactly the same.