Close encounter

This week, the moon seems spectacularly big in the sky. What's going on? Renowned astronomer Patrick Moore explains the phenomenon of the moon illusion

Friday June 24, 2005
The Guardian

For the past two evenings there has been something rather interesting in the sky. We have seen a very good example of the famous moon illusion. When the full moon is low down, it appears much larger than when it is high in the sky. This was noted many hundreds of years ago, and was even described by Ptolemy, the last of the great astronomers of ancient times. The effect is very noticeable; the full moon really does seem larger when near the horizon, yet this is pure illusion. The low-down moon is no larger than the high-up moon, as is easy to prove by a simple experiment: select a small pebble or coin, hold it out at arm's length and make it cover the moon; try this when the moon is low, and again when the moon is high - you will find that there is no difference.
Why should this be so? Ptolemy believed it was due to the fact that when the moon is low we see it across filled space, and we can compare it with trees, houses, or anything else. When the moon is high there is nothing with which to compare it; and this is why, according to Ptolemy, it looks smaller.

Basically, Ptolemy is probably right. The phenomenon is a little more complicated than might be thought, and indeed many articles and at least one book have been written about it. But it is certainly very interesting. You can see the effect at any full moon, but this week it has been particularly well seen, because this full moon has coincided with the time of the summer solstice, when the midday sun is as high as it can ever be. Obviously, the sun and full moon must be exactly opposite in the sky, so since the sun is at its highest the full moon must be at its lowest. This coincidence happens periodically, but certainly it does give us a particularly good chance to see the celebrated moon illusion.

I have seen the illusion more times than I can count, because, as I say, it is seen at every full moon. This month's event is in no way unusual, but it has aroused a great deal of popular interest. No doubt, the astrologers will have something to say about it, but the only way to describe astrology in the right language is to say "nonsense". It is surprising that even educated people still sometimes confuse astrology with proper astronomy. Last month, I published a little book called Stars of Destiny (Canopus Publishing), a scientific look at astrology. I even created my own zodiac. You may not agree with me, but at least I have tried to put the whole thing in perspective.

So, let us hope for a clear sky tonight, when the moon is still almost full and seems to hang just above the horizon. It is indeed hard to appreciate it is just an illusion and nothing more.

Consider also this:
...wait - where are my spectacles?......

Ok. thats better.... >a-hem!<

When viewing a lunar object that is overhead from the earths surface one is looking straight through the earths atmosphere...perpendicular-wise.

When one views the same object alond the horizon one is looking through much more atmosphere due to the angle of view.

There are particles in the atmosphere which refract light. - like a flashlight in a smoke filled room.

I asked my dad the same question when I was 5. He busted out his spectacles.

GEEK.

Click to view attachment

Funny thing was that Scott and I had this conversation just the other night while on our way to see (of all things) Batman Begins and I asked him the same question. He reached for his spectacles and then explained the exact same thing he posted. I had asked him if he thought there was anything to the full moon and people's behaviour, and he again reached for his spectacles....

Its theraputic to "poindexter-out" now and again.

Better than talking "Jerry Springer" on a daily basis,eh?

Guess everyones got their area of geekdom... Laureen is a photo-geek, Steves kinda a food geek, Duncan's a castle techno-nerd, AJR's the walking castle picture encyclopedia,
and the Mech? ... uh....
(mid-western drawl) "Well I knows about 'dem dare cans o' monkey grease!..."

And you failed to mention your little nook in the geeky world, so what would it be?

(childish giggle)
when I was in grades 5-7 I was often made fun of due to my larger vocabulary.
Got called different names including "Dictionary Brain".

Then there was the Macgyver era; known for creative ways to destroy things and blow them up. Also came up with many already-invented items (including that LAW rocket) this is like ages 12-17

My geek nitch really would be in the realm of logic and reason.
Things are usually quite simple and understandable. Its lies that are complicated.
When some "learned proffesional" tries to pitch you his complex theory of why something is the way it is and it doesnt make sense there is almost always a lie in it somewhere. Truth is simple. And the senior truths are very very simple.

Like Einstiens stuff.... sounds really Authoritarian and really learned (and nothing against the man as I havent even studied enough of his work to have a well rounded opinion) ....BUT,

I do know this:
1) His Theory of relativity is "difficult to understand" - according to people at large.
2) That theory has as part of it that "light is a constant" - which it isnt.

For the nerd crowd that is geeky enough to want to read further: Light cannot be a constant for at least this reason - when white light travels through a prism it slows down. It is the slowing down that creates the effect of a visible spectrum of color. (Color is different wavelengths of light) Hence the speed of light is not a constant - it is variable. Things that have un-truths in them are complex and not easily understood.


I also went to school in Connecticut and used to wear long sleeve plaid shirts. So there. Im a bone fide geek by heritage.

guess I was at least spared the geekdom classification. Haven't decided as of yet if this is a good thing or a bad one....

FYI...Einstein actually lived in Lynn for a while...right down the street from me. He did some stuff at GE. Odd but true.

Figures...

And BAHHH!!!
Everyones got some kind of geek in them...somewhere.
...even if youre geek at making toast or some such thing.

Those people who claim that they havent been classified as geek are really "closet geeks".

<-- CLoset geek who just came out....

Laureen,my Dad worked at that GE plant for most of his life as a jet engineer. He helped design the famous F-14 jetfighter. Did a lot of work on the engine itself in fact. I used to go there on family days to "see what Dad does" every year. Pretty neat stuff. As for the Fourth of July, I was, ironically, enslaved to doing work on the house most of the day. I learned some tiliing, was good and then some grouting today. Learning a new trade is nice for a change. There is lots of room for knowledge expansion. Cooking has become a little drab as of late, so its a nice change. I'm looking forward to diving in more when my cooking shedule goes down after next week.

Thats right. I forgot you used to live here! Small world. Sounds like you are aquiring a new skill set...nice....I need to learn that stuff. I'd like to be doing some of that here but I'm affraid I'll botch it so bad I will cost double the amount to fix the mess.

Galla -- I am glad I also was spared the geek classification.

Laureen -- all the good stuff seems to happen back East.

Yes and no. Depends on your view. Baseball is good over there right now, eh Laureen? Sox in first place and Manny just one hit away from beating Lou Gherig's all time grand slam record. Nice, huh? Can't wait until play-off time. Maybe we should come visit again during the series....OR you could get your ass over HERE. before I throw you in the ring with Scott....

Yes...they sent Foulke to the disable list! I like the guy buy geez...can't handle him losing games in the 9th....what do you think about Schilling? I have my doubts about him coming back and being as good as he was...
Yes, I'd love to get to HI ....maybe I can try to swing a visit in the fall ....I have the Paris trip coming up in April so we'll have to see.

Whatever we can work out for you to get over here. Curt,...I don't know either. Any injury isn't going to make you better. I just hopes he gets to play the rest of the season without difficulties. I have'nt had a chance to check the scores lately....who won the Orioles game on Thursday?