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Well, it seems to be a little too cold and too windy to throw the disc around today (at least for those guys). I figured that by the time I had to chase down a couple of throws, I would've been feeling a little warm.. but oh well.
I think it's time for the daily Science Teasers. I've run out of good ones, but hopefully this one will be easy enough to solve:
"Proof" That the Earth Stands Still
Centuries ago most people found it hard to believe that the Earth turns. No one could feel the turning, and there was no clear-cut proof of rotation.
Scholars reasoned that if the Earth were moving, a stone dropped from the mast of the ship at sea would be left behind as the deck moved forward and it would land some distance from the mast. Yet when stones were dropped from a ship's mast, they always landed directly under it. Scholars therefore argued that the Earth stands still.
[Is there anything] wrong with this argument?
Let's see if everyone gets this one right this time.
Monday, May 15, 2000 at 18:44:58 (UTC)
I feel I must redeem myself.
I quote:
Which is, of course, Newton's First Law of Motion. Applied to this situation, the stone dropped from the mast of a ship has, before it is dropped, is traveling on the same velocity vector (uniform motion) as the moving ship, which has as a component the vector of the moving Earth (and the moving Solar System, and the moving Galaxy, etc. up until we find something we're pretty sure can't move, but probably does).
That initial velocity doesn't change by the action of dropping the stone, since the only force acted on it (ignoring drag) is that of gravity, pulling it directly to the center of the Earth.
FlyingS<e-mail>
Monday, May 15, 2000 at 19:11:18 (UTC)
Ugh.. seeing as my batting average is 0 so far, I'm wary of answering.
But yeah, Newton's first.. momentum and all that jazz hasn't been taken into account by those scholars.
QYV - why don't you just build a column alongside yours for comments? In lynx, it'll put them underneath automagically. Having another page for them is sorta annoying as people will have to flip back and forth between the two windows. I suppose they could have two browsers open, but will the second window update when they travel to a different day?
Eh, I could go on about the virtues of having the most recently changed items at the top of the page (reverse chrono), but who wants my advice? According to Reg, no one.
Of course, you could be really evil and put the comments in a frame --it'd be a script calling a script that itself calls two scripts.
Dr. Hwansworth
Monday, May 15, 2000 at 21:20:59 (UTC)
(That whole thing about the Earth and relative velocities, by the way, is why I really hate that TV commercial that start off "What moves at [such-and-such] miles an hour?" Ugh! You can't compare the velocity of a fighter jet to that of the Earth! And what is that Earth velocity relative to? (The Sun, probably, but it does beg the question...)
Sorry, I've had that little frustration pent up for almost a year now... Need to vent.
FlyingS<e-mail>
Monday, May 15, 2000 at 21:32:16 (UTC)
The parabolic trajectory of the falling object wouldn't exactly coincide with the arc-length traversed by the base of the ship's mast. I don't think the Newtonian explanation QUITE fits.
I originally was going to say that maybe the distance travelled by the surface of the Earth in the time the block falls was negligable.. but I did the calculation and that doesn't seem true:
Assuming a mast height of 10 meters, the block is in the air for sqrt(2) seconds, during which time the mast has travelled *668 METERS* in the direction of the Earth's rotation (because the Earth's angular velocity is about 0.004 degrees/second and has a radius of ~6500km).
I guess in this particular teaser, the "obvious" (to armchair physicists like us) answer is right! hmm!
Reg Erastothenes<e-mail>
Tuesday, May 16, 2000 at 02:56:40 (UTC)
I think the "obvious" classical layman's reaction to the whole Earth-is-moving argument goes something like: "The Earth can't be moving, 'cuz if it did, we'd all fly off!" At this point we learned fellows all laugh at our foolish forepersons.
FlyingS<e-mail>