Why does the moon look closer on some nights and further on others?

Question

Sometimes the moon looks and also it looks so red too? Whats the explaination for this?

Answer 1

Because it IS closer on some nights and it IS furtheraway on other nights! The Moon's orbit is not a perfect circle but an ellipse. and as a result its distance from earth varies at different times in the monthly lunar cycle.

When it is at ts nearest to us it is called perigee. When it is at its furthest from us, it is called apogee. There are 13 perigees and 13 apogees in a year, i.e. one or other of these, once a fortnight.

This link to a pair of photographs (the Moon at Perigee and the Moon at Apogee) shows you how dramatic the difference can be:

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

and you can see from the table below for 2007, how the apogees vary from one another, as do the perigees, and the kind of difference in distance involved between the closest perigee and the farthest apogee.

Perigee............................ Apogee

.............. ............ ............ Jan 10 404334 km
Jan 22 366928 km...........Feb 7 404989 km
Feb 19 361439 km...........Mar 7 405850 km
Mar 19 357815 km...........Apr 3 406326 km *
Apr 17 357137 km **........Apr 30 406208 km *
May 15 359392 km...........May 27 405456 km
Jun 12 363777 km............Jun 24 404538 km
Jul 9 368533 km............. Jul 22 404150 km
Aug 3 368891 km............Aug 19 404620 km
Aug 31 364173 km...........Sep 15 405644 km
Sep 28 359419 km...........Oct 13 406489 km *
Oct 26 356754 km **** ....Nov 9 406670 km ***
Nov 24 357195 km ** ,,,,,,Dec 6 406234 km *
Dec 22 360816 km

KEY
* approaching the most distant apogee
** approaching the closest perigee
*** most distant apogee of the year
**** closest perigee of the year

Looking at the October 26th perigee and the November 9th apogee, you can see how the difference is 50,000 kilometres on top of 356,000 kilometres, a matter of 14%.

Take a couple of photographs on those two dates, and see the difference for yourself and document it for others!

The change in apparent size and distance is imperceptible from one day to the next, but viewed a fortnight apart, as I am suggesting, the difference is considerable.

Answer 2

Near the horizon, the moon appears to be a lot larger than when it is overhead. However, if we took a telephoto image of the moon at both times, and compared the images, we would see that the size is exactly the same. Therefore the effect is some sort of optical illusion.

One theory is that it is the angle of our eyes in our head that causes the effect, and if we were to lean backward on a plank, and look at the moon when it was overhead, then it would appear larger. This is not now the preferred theory.

A more accepted theory is that we tend to think of the sky as being bowl shaped, with the sky seeming further away near the horizon (near the horizon, things appear to be 'way over there', but overhead they seem to be 'just up there'). However, although this is a strong feeling , it is incorrect; and the sky and any astronomical object in it is exactly the same distance, whether overhead or near the horizon.

Therefore, because we expect the moon to be 'further away' near the horizon, we expect it to be a lot smaller than if it were overhead. However, because the moon is actually the same size near the horizon, our brain compensates by interpretuing it as being larger.

Exactly the same can be said of the sun, although of course it is dangerous to look at the sun, particularly when it is overhead.

A lot of people think the moon IS a lot larger near the horizon, because the atmosphere acts like a lens; but this can be shown to be incorrect by photographic comparison.

Answer 3

Nice handle, lil' Robotos.

I prefer the explanation that is dependent on the idea of the atmosphere and its relation to the moon having more to do with the air quality and our perspective from specific angles, than the ocular explanation offered by laser light enthusiasts.

The moon will look closer from the bottom of the month when the sea level is closer to the moon because of the way the tides react to the magnetic forces of gravity as it pulls and pushes water like a trapped bubble out of the "normal" position of sea level. In other words, when we see a full moon, particularly in the fall, which is also known as "the harvest moon" or "moon lady" time, the earth is at the three-quarters path perpendicular to the point at which magnetic north can counter-balance the autumnal equinox. If you can imagine all the crazy angles at which rotation is often off to keep the moon from being full at any part of the month, you might be able to further imagine how seldom it might be that the moon will align so perfectly closest to the earth at inexactly the same time in a year. In fact, if you can keep calculating these crazy numbers, you might be able to prove or disprove the theories about time contracting or expanding with the universe.

The moon might also look red when, like that strange angle when the sun turns the sky purple, orange, and crazy shades of dusk, the moon is reflecting that strange angle for an extensive period of time. If you had all the patience in the world, you might consider creating a model of this with Swiss-clockwork precision if it hadn't already been done before with computer animation and real engineers and wizards back in the day.

But what I'd be interested in knowing is whether or not someone can prove that there was truly a "blue moon" at any historic day or time from any inhabited country, because sometimes it seems to be the most unusual color, and it makes me wonder about the plausible natural existence of "black lights" which as far as I know only occur with flourescent lights.

Answer 4

The moon is actually the same size in the sky at all times, even if it appears larger. If it appears larger its just from a trick your mind plays on you when the moon is closer to the horizon.

You can test this... hold your thumb out at arms length and compare the apparent size of the moon to it when its high overhead, and then repeat when its near the horizon.

The difference in coloration is from the refraction of sunlight through the earth's atmosphere when the moon is close to the shadow created by the earth..

Answer 5

The moon is the arth's satellite which revolves around the earth in its elliptical orbit or path. That explains why it looks closer or nearer on other days. The color differences can be explained by the combination of gases in the horizon creating a visual color illusion. This is also applicable to the different sunset appearance in different areas. It is also indicative of the level of pollution in the area where it will appear darker or intensed hue when the area is more polluted.

Answer 6

Our eyes and our brains. When the moon is at the horizon, our minds think that it's farther, so we assume it must be really big in order to be that far away and still visible. However, when it's high in the sky, it seems smaller because there's no instinctive visual cues to tell us how far away it is. It's actually visually the same size. Hold up an object like a pencil eraser that covers it completely, then hold it up again when it's higher in the sky. It'll be the same size - it's all in your head.

Answer 7

The moon changes size by about 4%. because it's orbit is eliptical. Not really enough to notice.

The Red color is from light refracting in the sunset.