Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**JadeH****Member**- Registered: 2016-10-07
- Posts: 9

having a big debate about this "flat earth" rubbish

person im talking to is claiming that the suez canal is 100 miles long so it would need locks in it to counteract the earths curve if the earth was round...

"The Suez Canal connecting the Mediterranean with the Red Sea is 100 miles long without any locks making the water an uninterrupted continuation of the two seas."

my side of this debate is 100 miles is way to small a distance to notice any difference when it comes to the size of the earth.

i googled it and the earth circumference is 24000 miles.

not sure if we need these but ill add them in case... earths radius is 3,959 miles km and diameter is 7,917.5 miles.

how do i work out how many degrees 100 miles is over a 24000 miles circumference?

im guessing its gonna be like 0.5 of a degree

24000 /100 /360=0.6666666667

is that the degree or have i messed my math up?

and how would i then work out how much of a drop that 100 miles would have from start to end?

im guessing it only will be acouple of inches

*Last edited by JadeH (2017-01-02 04:07:58)*

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

I would think it is more than a few inches:

https://en.wikipedia.org/wiki/Horizon

I have read but not computed that the earth curves down 8 inches per mile.

Congratulations to the person you are talking to, I have never heard that argument.

From a very simple argument I am getting about 1.2 miles for 100 miles away?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

**JadeH****Member**- Registered: 2016-10-07
- Posts: 9

god dame it! my math is miles out

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

That is only true if my calculation is correct as I did an along the surface of the earth 100 miles.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,137

hi JadeH

If the Earth is a sphere then the gravitational pull is towards the centre. So the canal could be curved and yet not experience any adverse flow towards the end points. Try thinking of the Atlantic and Pacific oceans as the end points of a 'canal' at Cape Horn. No locks there.

Bob

ps. Eratosthenes worked out the curvature of the Earth in 3rd century BC https://en.wikipedia.org/wiki/Eratosthe … cumference

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**JadeH****Member**- Registered: 2016-10-07
- Posts: 9

im totally confused about this 8" drop now...

bobbym how did you get 1.2 miles?

using google converter 8 inches = 0.000126263 miles

then multiplying that by 100 gives you the total drop of 0.0126263 miles over 100 miles

have i miscalculated?

i admit im not good at conversions and i think ive messed up somewhere

ive already hit him with the gravitational pull and how you can see farther the higher you are (distance to the horizon)

reading that bit about Eratosthenes is insane! ty bob bundy "the more you know"

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

The drop increase is not linear. The further you get away from the starting point the drop becomes more extreme. The calculation was done with geogebra and is about 1.26 miles. Of course, since I can not verify it by using another method, I am only offering it up as a refutation of the few inches comment.

Basically, I did this. The image is not to scale else we could not see it. I started at B which is (0, 3963) and then marked of 100 miles arclength. This put me at C. I got C's y coordinate which was about 3961.73 and subtracted that from 3963. That is how I got 1.26 miles approximately. This "drop" is purely a geometrical consideration.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,137

??? Why is the bit about Eratosthenes 'insane'? If the Earth is a sphere down is towards the centre of the Earth. So all that water is being pulled down equally. There is no point on the canal that is 'lower' than any other. Here's a non scaled picture:

Where would anyone put the locks?

As for the angle: 100/24000 times 360 degrees = 1.5 degrees at the centre. That is also the angle between a tangent at one end of the canal and a tangent at the other.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**JadeH****Member**- Registered: 2016-10-07
- Posts: 9

oh ok

i kinda get it now

i was hoping there was some simple formula of working this out

im gonna give up on it as this is way above my math and science knowledge now and im getting more and more confused

ty for your help guys i do appreciate it

i still dont believe the earth is flat and personally i think the whole idea of a flat earth is ridiculous! but i do see they make some good points in there arguments of claiming its flat... <3

Offline

**JadeH****Member**- Registered: 2016-10-07
- Posts: 9

insane to comprehend as Eratosthenes did it over 2000 years ago without modern tech he even made columbus look like a fool 1700 years later as columbus thought the calculation was out ^_^

to me that is "insane" (another term for impressive... its not me saying he was "insane" as in crazy)

*Last edited by JadeH (2017-01-02 06:59:11)*

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

i still dont believe the earth is flat and personally i think the whole idea of a flat earth is ridiculous!

A whole different point and one that certainly leads to strange and different ideas. I have never seen anything but a picture of the round earth. The flat guys make some difficult arguments to unravel, this does not prove their assertion. At the present time based on being an EM guy I have not seen a convincing experiment either way. I mean one where I would jump up screaming, the world is round, the world is round. Fortunately, the earth does not care and each day I wake up more and more glued to it.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline