State of the World

[vakkotaur]

First, let's get this taken care of. A while ago I wrote, not all that well, about some of the events of a certain day a couple years ago. There are plenty of people affected by those events, but I do hope someday that while it may be remembered, that the date of September 11 is more just another day again.

Now, on to the state of the world. I do not mean the political state, nor the economic state, nor even the environmental state in the commonly used sense. I mean the very basic physical state.

When young, people are now taught that the world, well the thing we're standing on anyway, is a planet which moves around the sun and is roughly round. People are taught that people once thought otherwise but now we know better. But, for the most part, this is taught and said rather than demonstrated.

Suppose, for a moment, I said something jarring, like "The Earth is flat." How would you prove me wrong? Or better, what would you suggest I do to prove myself wrong? Now I don't happen to have a spacecraft handy to tool around in and check the shape from space. And I'd prefer not to rely on others at all, or at least as minimally as possible. This seems like it should be a really simple thing, it seems so fundamental. That is, until you start thinking about it and don't want to take what someone else says for granted. What could an average person of average (or even less than average) means do to prove to himself that Earth is not flat?

I asked someone this and got a reply asking if I'd seen a lunar eclipse. I have. I have seen several, in fact. And yes, the shadow on the moon is curved. That shows a curve in two dimensions does exist. It doesn't prove a sphere, not right off anyway, as it could be argued that it is the result of a disc.

No, I haven't gone flat-earth crackpot from reading Pratchett. This is more of a Feynman curiosity and desire to know something because I checked it it myself, rather than relying on any authority. That's the difference between believing and knowing. Wouldn't it be nice to know?

Comments

[vakkotaur.livejournal.com]

Simple travel in and of itself proves nothing. I do expect travel to be involved somehow for some methods though. Measurement of some kind at different places, that sort of thing. Not that I'd mind a world trip - well, there are parts I'd steer clear of - but that's a bit of an expense in both money and time.

[jdm314.livejournal.com]

As for the Lunar Eclipse, the critical point is that the shadow is always round, no matter where the sun and moon happen to be in relation to the earth. If the earth were disk shaped, we would sometimes get a line shaped, or at least cat-pupil shaped shadow on the moon. Of course that might be a bit elaborate to prove, since most people don't see dozens of eclipses.

The other standard item cited as evidence is the horizon. In ancient Greek sources the example given is a boat saling away on the open sea. As it gets farther and farther away it appears to get smaller and smaller, without changing shape. But instead of continuing to shrink until it is too small to see, as we might expect if the earth were flat, after a certain point the bottom of the ship starts to disapear under the horizon, and slowly this continues until the whole thing is gone. This is because the curvature of the earth is getting between the observer and the ship. And trust me, the ship hasn't fallen off the edge of the earth- I've seen many of them come back ;)

[vakkotaur.livejournal.com]

Yes, that would do very nicely. Not to be obstructionist, but I don't happen to have an ocean handy here on the plains. Perhaps I should rephrase the question: How would you teach this lesson to kids (pick an age) where they figure out the result for themselves?

[pharwarner.livejournal.com]

I would also suggest the method of watching a ship sail over the horizon. I find seeing a square rigger coming towards you over the horizon to be the best (and most spectacular!) way to show up the curvature of the earth. But then that does need more than one person... Maybe walking towards a steep mountain range would allow you to see the same effect with no input from other humans at all.