Prove the Earth is round

[Kumar]

Hello phildonnia,

Nice picture. What is this? It is flat on my screen.

 

[Crossbow]

There is one idea for proving that the Earth is round that I have not seen discussed yet.

Take an object to a fixed distance above the ground and let it drop being careful not to let wind or other actions change interfere with its motion.
Then, move some horizontal distance away and let the object drop to the ground in the same way.

Now very carefully measure the horizontal distance between the respective release points and the impact points.

If the Earth were flat, then these distances would be equal.
However, since the Earth is round the impact distance will be less than the release distance.

Further, knowing the difference between the horizontal distances and the vertical distance that the object fell, one can actually measure the size of the Earth. Also, since the same value for this calculation will result regardless of the direction between the first and subsequent drops, one can determine the Earth is round.

 

[Correa Neto]

Someone please tell me I am not seeing a debate Kumar x the world regarding the shape of the Earth... It has to be a bad dream...

Please tell me that there´s something else...

 

[roger]

well, it's not much different than the .9... != 1 argument, now is it?

 

[Rocky]

If the Earth were flat, then these distances would be equal.
However, since the Earth is round the impact distance will be less than the release distance.

The rotation of the earth will affect the results in a small but important way.

 

[Rocky]

My Devil’s advocate view of a flat Earth would be a disk with the North Pole at the center. You could go east or west forever and north to the pole with out falling off the edge. This shape for a flat Earth could cast a round shadow on the moon.

To prove this view wrong: Study the night sky; note how it appears to also be a disk centered at the North Pole. Now travel south (being careful not to fall of an edge) and studying the sky each night. Soon you will discover that you are under a new disk centered on the South Pole. You are now on the bottom of the Earth. Still a disk, but safely having avoided the edge!

(Friends in the bottom hemisphere can reverse these instructions)


)snoitcurtsni eseht esrever nac erehpsimeh mottob eht ni sdneirF(

!egde eht dediova gnivah ylefas tub ,ksid a llitS .htraE eht fo mottob eht no won era uoY .eloP htuoS eht no deretnec ksid wen a rednu era uoy taht revocsid lliw uoy nooS .thgin hcae yks eht gniyduts dna )egde na fo llaf ot ton luferac gnieb( htuos levart woN .eloP htroN eht ta deretnec ksid a eb osla ot sraeppa ti woh eton ;yks thgin eht ydutS :gnorw weiv siht evorp oT

.noom eht no wodahs dnuor a tsac dluoc htraE talf a rof epahs sihT .egde eht ffo gnillaf tuo htiw elop eht ot htron dna reverof tsew ro tsae og dluoc uoY .retnec eht ta eloP htroN eht htiw ksid a eb dluow htraE talf a fo weiv etacovda s’liveD yM

 

[DickK]

Sorry, I'm not a physicist or anything, nor am I interested in proving, to Kumar's surreal and obtuse fascination, that the world is round.

Is it permissible to use another well-formed idea as a basis for proof, or is that constrained by the "no proof by example" thing? Say, notions of Newtonian gravity and mass, that provide a system of models that are understood well enough to propose that, a spherical Earth would permit activities like running and jumping in the way that we observe them, and that a flat earth, er, would not.

I'm assuming that "he made it that way to test our faith" is an inadequate counter.

 

[Crossbow]

The rotation of the earth will affect the results in a small but important way.

True, but that is only significant when the falling distances become quite large.

One could also argue that there are other factors which will have an affect as well such as the non-uniform gravitational field of the Earth, tectonic plate movement, etc.

 

[TillEulenspiegel]

Cute anicdote ( paraphrased from memory )

C.Sagan gives a lecture at the end an old lady comes up and tells him his model of the universe is poppycock, " everyone knows that the world is supported on the back of turtles". So Carl asks what is the last turtle resting on?", "why another turtle of course!"

 

[dsm]

Take an object to a fixed distance above the ground and let it drop being careful not to let wind or other actions change interfere with its motion. Then, move some horizontal distance away and let the object drop to the ground in the same way.

Doesn't this presume a stable Earth? For instance, if the flat-Earth is moving through space on the back of a turtle, then the distance between release points will be different than the impact points. Whether the difference will be greater or smaller depends upon the direction the turtle is moving.

True?

 

[CurtC]

TillEulenspiegel, you gonna tell the rest of the story, or leave everybody hanging? There's a memorable punch line that goes with it.

 

[phildonnia]

Is it permissible to use another well-formed idea as a basis for proof, or is that constrained by the "no proof by example" thing? Say, notions of Newtonian gravity and mass, that provide a system of models that are understood well enough to propose that, a spherical Earth would permit activities like running and jumping in the way that we observe them, and that a flat earth, er, would not.

I don't think so; our understanding of gravity was formed by a need to explain the facts; among them, that the earth is round.

 

[Zep]

You are just repeating my question in other way. However you have not mentioned 'per- Km,meter,inch,cm,mm etc. so that others to measure & give reply.

No, I'm asking you, not them. Your results will help form my answer. Go find a tennis ball and measure it for me, please. A cricket or hockey or baseball or something of that size will be just as sufficient.

Will you actually do this and report back to us all what "slope" you measure for one of these objects? Not just sit there in front of a computer and waffle on? Yes?

 

[TillEulenspiegel]

No fight. But how about a conversation to sort out, or clarify, what we are trying to say and possibly reach a mutual understanding?

So yer saying there is a net force downward (due to gravity) and thus the airplane is accelerating in that direction?



[obligatory pedantic content]

BTW, typical gross weight of a 1969 Cessna 150 is around 1600 lbs., and sitting in the hangar with no fuel, occupants or baggage, the empty weight is about 1100 lbs. Give or take a few.

[/pedant]

Ahh HA!
not only do You start to reveal the approximation of your age , I see that your humor organ is equal in size to mine.

Well net forces, your discription is correct for a parked airplane , a net force downward with all others at zero ( unless the damn thing is facing the leading edge of a hurricane in the open.)

Cessna 150 was a long time ago for me , maybe that was the gross weight limit <shrug> are your bushes square and your albums arrainged in alphabetical order ?

 

[phildonnia]

TillEulenspiegel, you gonna tell the rest of the story, or leave everybody hanging? There's a memorable punch line that goes with it.

Something like
"Oh, no, I see where you're going..."

 

[xouper]

Zep: No, I'm asking you, not them. Your results will help form my answer. Go find a tennis ball and measure it for me, please. A cricket or hockey or baseball or something of that size will be just as sufficient.

Will you actually do this and report back to us all what "slope" you measure for one of these objects? Not just sit there in front of a computer and waffle on? Yes?

If I may be permitted to rephrase Kumar's question, he is asking if you extend a line out over the ocean (tangent to where you are standing), how far above sea level will the end of a one kilometer line be? I believe that is a reasonable interpretation of his use of the word "slope" in the manner he asked the question.

You may argue that this "slope" varies with line length and you would be correct. You are also correct that a curve has no overall slope. But it does have an instaneous slope at any given point, and that is what I think Kumar had in mind - what is the instantaneous slope of a point on the ocean one kilometer away.

 

[TillEulenspiegel]

NONONO wait!
Your all taking the wrong approch, Agamemnon taught me this. Your over anal-izing it and trying to exceed the scope of the question.
The thread topic was to prove that the earth is round. The picture from space conferms it!!
No one asked to prove that it is sphearoid! they asked if it was round. and by golly it is ! you-reaka

 

[xouper]

TillEulenspiegel: Ahh HA! not only do You start to reveal the approximation of your age , I see that your humor organ is equal in size to mine.

Apparently so. For the terminally curious, I was 20 when I got my PPSEL in 1974 in a (then) 15 year old Cessna 150. It had a straight tail and a big ol' johnson bar between the seats for manual operation of the flaps. I haven't seen that plane since 1977 and I can still remember the tail number, 5858E, but I can't remember what I ate for lunch yesterday. And no, my albums (cds) are not yet in alphabetical order because I just unpacked them three months ago and I haven't gotten a round tuit.

 

[Zep]

If I may be permitted to rephrase Kumar's question, he is asking if you extend a line out over the ocean (tangent to where you are standing), how far above sea level will the end of a one kilometer line be? I believe that is a reasonable interpretation of his use of the word "slope" in the manner he asked the question.

You may argue that this "slope" varies with line length and you would be correct. You are also correct that a curve has no overall slope. But it does have an instaneous slope at any given point, and that is what I think Kumar had in mind - what is the instantaneous slope of a point on the ocean one kilometer away.

Seriously, Xouper, you are making it a REASONABLE question and would be expecting a REASONABLE answer. And I'm sure we could calculate acceptable stuff by that or any of the other REASONABLE methods proposed above.

I would expect, however, that if we DID respond with a reasonable answer to this restated question that Kumar would then pull some inane and insane response out of his hat/bum that he believes proves that we are lying/stupid/wrong.

Kumar is basically using the tactic of gainsaying any and all methods of calculation being proposed, which is being UNreasonable. If he were serious then he would be at least listening and discussing, but he is not. My opinion, previously stated quite clearly, is that he is a troll.

HOWEVER...

If he wants to continue to play this silly game then he can go do what I ask for a change. Thank you for restating his question sensibly, but the ball is definitely in HIS court.

 

[SquishyDave]

Cute anicdote ( paraphrased from memory )

C.Sagan gives a lecture at the end an old lady comes up and tells him his model of the universe is poppycock, " everyone knows that the world is supported on the back of turtles". So Carl asks what is the last turtle resting on?", "why another turtle of course!"

So Carl asks, "And what is that turtle on?"
"why another turtle of course!"
"And that turtle?"
"Oh no, I see where you're going, and you can't fool me, it's turtles, all the way down."

What can you say to that?