Getting intelligent, well-educated people to argue with her; and then have those people lose those arguments, must make her feel wonderful.
This lady may have very low self-esteem, and therefore uses this as a ploy to gain atttention.
Quite probably, she is very lonely, or suffers from clinical depression.
Ignore her occasional odd idea.
She needs a friend.
I take it from your above statement, that you are implying that the crescent shape of partially-full moon is caused by the earth’s shadow. But the shadow of the earth doesn’t cause the moon’s phases… The moon’s phases are caused by it’s position in relation to us and the sun.
It’s sort of like holding a ball and a light source, one in each hand. As you move the light source around the ball being held in one place, you notice that the amount of “fullness” of the ball changes. Light from front of the ball in your perspective makes it appear “full”, and as you move the light around to the back, the “phases” of the ball change until it is all dark from your perspective.
So if it with the moon, the sun, and earth. The Sun in relation to our perspective lights up more of the moon’s surface in our view until it is “full” and then less and less until none of it is lit from our perspective.
The only time the shadow of earth touches the moon is during a lunar eclipse.
Sorry to go off topic, but I had to mention that.
Ummm… please explain to me why the centre of gravity doesn’t apply to the pendulum.
“His daughters friends’ mother seriously believes the Earth is flat.”
Tell her to get up off her ass, have a shower, put some decent clothes on, and step in to the 21st century.
Damn it to the bowels of bloody hell! I must start reading all responses before I reply…
My apologies, although I do hope my answer was helpful, at least a little bit!
Stupendous Man!
[QUOTE]
*Originally posted by Lemur866 *
**
Yup. To be precise, that well was in the Egyptian city of Aswan, and was located on the Tropic of Cancer.
What the Tropic of Cancer is, is the line on Earth where the sun is directly overhead at noon on the Summer Solstice. (Since the Earth has an axial tilt of 23.5 degrees, the tropics of Cancer and Capricorn are at 23.5 degrees north and south.) Between the Tropics, the sun is at the zenith at noon for part of the year around the Summer Solstice (which is, of course, in December in the Southern Hemisphere.) Outside of the Tropics, the sun is never at the zenith at any time of the year. That’s because since the Earth tilts on its axis 23.5 degrees, it’s 23.5 degrees off from the straight rays of the sun, and so only parts of the world between those angles of latitude form a straight line between the ground and the sun. If the Earth had no axial tilt (like Mercury almost doesn’t), the sun would never be overhead anywhere but the Equator, because the Equator would be the only place where the ground ever points right at the sun. (Also, we would have no seasons.) Conversely, if we were tipped over on our side at 90 degrees of axial tilt (like Uranus almost is), …well, i’ve been dicking around with this for a while and I can’t figure it out, but I assume that everywhere would be a potential zenith location. Also the seasons would be completely fucked up.
Anyway, Aswan is’t exactly at the Tropic of Cancer, and neither was Erastothenes’ calculation exact. But it did give the circumference of the Earth according to the shadows of the sun. It’s also my favourite easy ‘n’ fun scientific demonstration. (I brought it up when I was having an infuriating argument with my cute but stupid ex-boyfriend when he claimed that it was Columbus who discovered that the world was round.)
That’s part of the problem, isn’t it? At a passing glance everything just looks round (pancake-style).
Personally, I blame the moon for this whole flat-earth debacle. If it had just had the decency to spin normally, people would realize it was a sphere and draw conclusions from there.
There’s no convincing some people. This woman sounds like one of them. Seriously, does it do any harm to allow her the illusion of superiority her belief in a flat earth provides her? Is it your responsibility to scour the neighborhood to find instances of wrong thinking and correct them? Seriously, if this woman wants to believe in a flat earth for whatever reason, it has absolutely no effect on the price of bread at the supermarket.
Personally, I can understand the concept of a round earth, and have heard and understand some of the theoretical arguments in favor of a flat (or other-shaped) earth. The math supporting non-round-earth theories is quite complex and (often) non-euclidean. Occam’s razor suggest that a round earth is the correct conclusion.
Since this woman is not in charge of any endeavor where belief in a flat earth is likely to cause any harm, I suggest the best course of action is to either humor or ignore this person’s quirk. A hundred years from now, it will make no difference what she believed.
~~Baloo
Speaking of the Umberto Eco connection . . . in Eco’s book Serendipities, his essay “The Force of Falsity” busts wide open the old chestnut that Columbus was trying to prove the world was round, since educated people had known that since ancient times, and all through the Middle Ages too, and that wasn’t even the issue at all. Columbus was trying to prove that the world is smaller than it really is, so he could sail around it in a few weeks.
The geographers knew the earth is way bigger than that, so he would never make it. Nobody figured on America being there.
So Eco, who has a taste for irony, drew the conclusion that because Columbus was wrong, he was right, and because his critics were right, they were wrong.
Erm… she’ll need a time machine to do this. It won’t be the 21st century for another couple of months 
As to keeping a Foucault Pendulum going… they don’t need to be nudged. I’ve never heard of that sort of thing. They do lose momentum and amplitude over the course of the day, though. I think the one at the American History Museum in DC (Yep, it’s at the AmHist Museum, not at the NatHist Museum. Go fig.) states that it’s started from a specific point at 10 AM every day. Presumably it’s pulled back outside the circle of pegs, and slowly its amplitude falls to just the radius of the peg circle. But a several-hundred-pound pendulum attached to a relatively frictionless cable that’s ten meters long actually will keep going for quite a long time.
Unfortunately, the Foucault Pendulum doesn’t prove that the Earth is round. It merely proves that the Earth spins, and could be a flat disk spinning around its center. For proof, get yourself a Spirograph Pendulum (I don’t know whether they make these any longer; they dripped sand out of a pendulum from an hourglass-like point at the end). Set it going straight back-and-forth, and watch as it forms a line. OK. Now take it to a flat, spinning disk, which most of us can find in our neighborhood park (those merry-go-rounds that are kid-powered, that is). Set it on the spinning disk, and get it going in a straight line again. Now spin the merry-go-round. Once it’s stopped, you’ll see that your miniature Foucault Pendulum didn’t stay in a straight line, but dropped sand all over a circle as the plane of its swing changed relative to the paper.
Now. In theory, a really large Foucault Pendulum at a normal inhabited latitude will not swing around in a circle at a constant rate, because of the curvature of the Earth (It ought to spin faster, if my quick thoughts are correct, at times when the plane of swing is aligned East to West). More interestingly, a Pendulum set up right at the equator should have severe problems. Physicists correct me if I’m wrong, but a Foucault Pendulum at the equator should stop after six hours, as its original plane of swing rotates completely out of the available planes of swing.
Indeed, as I think about it a Pendulum at any latitude except 90° North or South will change its amplitude slightly because it’ll be trying to match an unavailable plane, and will have to drop energy matching the cosine… yeah. If I want to sound right on this bit I’d better actually go do the math.
Of course, trying to explain said math to a person who believes the Earth is flat would be useless, and won’t help you in proving anything. An extremist might believe that people like this should be sterilized and prohibited from voting or mingling with the rest of the world, but there’re no extremists around here.
LL ← thinks he rambled too much about pendulums.
Just to clarify, it’s not that the signals are AM (or amplitude modulated) or FM (frequency modulated) that lets it curve with the earth’s surface. What matters is the frequency. ANY modulation type at low frequecies will tend to hug the earth (ground-wave propogation). It just happens that FM is used mostly at higher frequencies, so you don’t normally experience it with FM stations. If you had an FM radio station at 1440 kHz, it would generally have the same range as an AM station at 1440 kHz.
While I’m posting, I might as well point out that just because you can’t find an edge to the earth, you can conclude that it’s a sphere. A torus (donut shape), for example, would have the property of no edge or definite boundary.
Arjuna34