Oranges and Earths

[Arch]

Or, start at a pole, and you only need one

No, you need to start with a chain joined round into a circle, so a minimum of 3...

 

[Landslide]

I'll leave it up to you to work out how many yards of yarn you'll need

 

[abchandler]

No, you need to start with a chain joined round into a circle, so a minimum of 3...

I shall log that as my craft fact of the day

 

[Arch]

I shall log that as my craft fact of the day

Glad to be of service.

I've got a feeling the OP intended this to be thread of contention akin to the ducks and the plane on the treadmill, so I feel a bit guilty about hijacking it with craft talk!

 

[purpleR]

It is the same for both, and it is, I think, about 16cm .. Which I find astounding... 40,000KM .. add a metre and it raises by 16cm !!!

That seems wrong. Are you sure? Let me see your working!

 

[purpleR]

Oh, I see the Doctor's working. I understand, but I don't really believe.

 

[Speicher]

It's about 6 inches . Use the formula for circumference of a circle
Circumferance = diameter times pi

If the circumference increases by a metre, or 39 inches, the diameter goes up by (39/3.14) inches or just over 12 inches, so the radius goes up by half of that.

Checking on a calculator...16 cm is right.

How long does it take to rise 16cm? If you lift one bit to 16cm above the earth's circumference - how long will it take for the rest of the string to respond to the lift effect. Do you need to extrapolate a wave effect, ie lift the string more than 16 cm to start. What is the velocity of the wave in the string? What about the string that has been in contact with water, as it gets heavy due to absorbing water? Will this affect the lift?

 

[dudi]

so what we're saying here is that if you add a metre of cord onto a cord around the circumference of a sphere, no matter what the size of the sphere, you will be able to elevate the cord 16cm the whole way round. or in other words, increasing the overall diameter by 32cm.

I find this very hard to believe, my brain is telling me i'm a fool too think it could be true. so i'll prove it.

what about a marble of say, 1cm diameter. apply Pi x D (where D = diameter) to achieve the circumference and you get 3.14cm (2dp)

add 1 metre to this and you get 103.14cm.

if Pi x D = 103.14cm

then D = 103.14cm / Pi

D = 32.84cm...

an increase of 31.84cm

deflection of 15.92cm


now apply it to a large sphere. say 4,000,000cm diameter

Circumference = Pi x D = 12560000cm

add 1m = 12,560,100cm

D = 12,560,100 / Pi

D = 4,000,031.84cm

increase of 31.84cm to the diameter.

deflection of 15.92cm



weird... defies all of my brains logic but certainly appears to be true...

 

[Arch]

How long does it take to rise 16cm? If you lift one bit to 16cm above the earth's circumference - how long will it take for the rest of the string to respond to the lift effect. Do you need to extrapolate a wave effect, ie lift the string more than 16 cm to start. What is the velocity of the wave in the string? What about the string that has been in contact with water, as it gets heavy due to absorbing water? Will this affect the lift?

What you need is a cooperative world community, all standing around the equator, perhaps with a foot or so between them, to lift the string simultaneously, on a count of three. You'd need people anchored in boats too, for the ocean bits. Shouldn't be hard to arrange. They could pass the old Olympic torch along at the same time perhaps.

Yes, dudi, it's almost impossible to believe isn't it, which is why I vaguely remembered it. It's almost more a riddle in those terms, like saying which is heavier, a kilo of lead or a kilo of feathers...

 

[Arch]

Oh, and I was casting on crochet chain stitches all night and have got to 4,567,972. And I have one hugely overdeveloped shoulder.... And all the shops have run out of yarn...