How? What are you suggesting?
If he's suggesting stretching a rope/string/twine type object the distance of 3 miles, then I think he's overlooking the dip that gravity will put in the rope, which will only muddy up your margin of error.
Something overlooked? You're absolutely right, gravity will pull the line down. This cannot work against a round earth argument. A line stretched above a body of water at, say, 3 feet of elevation must touch the water at the center point if spanning 3 miles. gravity pulling the line down will only add to this dip. But what if the line wasn't touching the water at all? I'm sure the first explanation out of the bag would be the newly discovered "antigravity rope/line effect" which has a measurable "center of taughtness"... lol
Well since the earth IS round then the rope is going to touch the surface. If you can't distinguish between the curvature of the Earth and the line's catenary, then it's not really very useful.
No matter what the experiment, it seems, this remains true.
Playing around with the calculator here:And I'm not sure of the exact math, but suspect that three miles of line would have WAY more dip in the middle than three feet. You've only got 100lb of force at the ends holding about six pounds of cable.
Why don't you give it a go with 1000 feet, and report back
While I don't view this as a serious topic, if one were determined to try it, wouldn't a better medium
If by taut you mean straight, then it is impossible. The sag will only be zero when the horizontal force is infinite.
I went with rope because I thought a boat spooling out fishing line and pulling away from where it is tied down would be easy to snap.While I don't view this as a serious topic, if one were determined to try it, wouldn't a better medium
--like the strongest, lightweight fishing line...extended ever so gently--
be more likely to succeed?
just straight up "NO it's not possible"... modern established science, in practice, at its finest. Does it really surprise that there's a growing host of plebs who question things, now, to such a degree that the shape of the world is back in question?
honestly, yes
It was labelled "No" after the discussion showed that no, it's not possible. Unless you have a magical weightless and infinitely strong rope then it is always going to sag far more than the Earth's curvature over a given distance.Love how the thread was titled after being split.
well let's replace "magic" with neutrally buoyant and place it in the water along its entire length. In a flat earth this rope or monofilament will remain fixed at its starting elevation along it's length. In a convex earth adding tension will cause the line to move lower into the water at its mid point.
Interesting idea. That might work. I wonder whether currents etc might complicate matters over a long enough distance to have a noticeable drop in the middle. You'd effectively be measuring the "bulge" height on the curve calculator, which is only 18 inches over 3 miles.
So how are you going to place three miles for line exactly one foot under the surface with zero tension?
I thought the idea was to have it floating on the surface of the water and then tension it and see if it goes under the water in the middle. So it would need to be slightly buoyant. But yeah, currents would put a lot of tension on it.
I'm trying to hone in on "definative"or" irrefutable" sorry if you find my "science a 10 year old can understand" "hard" ...and what's this "possibly" you speak of within 10 miles of my house there is a shallow, stagnant, body of water nearly 5 miles across... This is the opposite of "hard" Mick. If there does exist currents in the water applying pressure can we suggest that this would not change the fact that applying tension should always pull the center of line down on a round earth?
Go on then. I look forward to the results.
It will pull it straight, pulling it into the chord position will be the LAST thing that happen, first you've got to counter the currents. I submit that even a very slow current would put more force on three miles of line than it would be able to hold. I'd be happy to proven wrong, as it would be a unique experiment.
Weightless test line is very hard to come by.
No lazers! Lake Balaton has shown us this error.
The laser is just adding complication. Just use a decent surveyor's level set up at the same fixed height at mark A, and sight to mark C. The mark at B should be above the level of C. (And both should be slightly below the true horizontal.)
you get it at the shop that sells stripped paint
Yes it is. You're the only one mentioning it. Neutrally buoyant, relative to freshwater, is another matter.
Indeed it is, but bringing water, with all its friction and unpredictable currents, into the equation just seems needlessly complicated.
There is going to be a number of problems to account for.
Ducks?
Can you post a link to the kind of line you have in mind?
You know this is why I love you guys at MB. Around here its considered "complicated" to take standard 100lb test line which is nearly neutrally buoyant ,as it is, and place a length of it into a body of water while stretching it out. (Not directed solely at you)... when considering the experiment can we at least agree that on a round earth: no matter the forces involved the only possibility is for the mid point of the line to move away from the surface in a downward direction. Current and any other lateral forces, upto the point of snapping the line, will add to this relative vertical downward motion in direct proportion? (With resistance forces like friction adding lag to the effect)...the only other possible results would be( flat model) the line stays at or near its depth, on average over time considering the other forces or it attempts, and likely fails, to break the surface tension at the mid point (concave model)...But why even set this up? There is no amount of testing that someone of my credentials can do to prove this to anyone other then myself. Lol, read the closed minded comments just on this thread...this experiment is so simple, so repeatable and so conclusive, the mind here is repelled. Consider how, off the cuff, the admin here answered the question postulated in the title of this thread with a "[no]".
At the surface I'd be contending with the strongest possible unwanted forces and conditions Especially the surface tension of the water. I belive the best possible location is a few inches below the surface at the points of tension.
Can you clarify this point for me @Greylandra (or anyone else). How can the line be moving away from the surface in a downward direction? Assuming the line is suspended above the water, it moving downwards is getting closer to the surface, not away, right?
Sorry. [ ...]... 3 miles of neutrally bouant, 100lb monofilament stretched taught a few inches below the water line at opposing shores.
It wont be. However in a round earth it will, in all cases move further from the surface as any tension is applied. The "straighter" we attempt to pull it the more the curve of the earth should be shown at the mid point.
