Hi,

I had this debate with my college friends today and it was pretty much half of the group vs the other half. Here's the theory:

If you had a peice of string long enough to circle the globe - Disregarding mountains and terrain changes (ie. a totally perfect sphere) - if you pulled this string tight, would it circle the earth without touching the floor? See diagram:



The red string is the theory that the other people have, and the blue string is what I think would happen.

Discuss, red vs blue.

Is it special levitating string or normal string?

Wow, this is an interesting one. But surely red would be correct because it's standard string-pulling, just on a larger scale.

Oh well, I ticked the blue string.

But then I thought that if we pulled the string, it would probably slip and the Earth would fall down (yes, the string had to be wider). But if I don't mind this, I think that it won't touch the floor.

the weight of the string would make it touch the ground. me finx blue.

Quote from J@tko :

Is it special levitating string or normal string?

Normal string

i say, if you're part of the gravitation of that globe, and the string too, then the blue one should be plausible.
If you and the string aren't affected by the globes gravitation, then the blue one makes sense.

cheers

Discounting mountains, valleys etc, the Earth isn't a perfect sphere, but an oblique spheroid. If you were able to pull the string tight enough so that it didn't sag under its own weight, then yes, it would touch all the way around.

If the string is stretchy enough so that it sags under its own weight, then no it won't touch everywhere.

I'm not sure that such a string exists that could maintain the required tension to touch everywhere without breaking or sagging.

What would fall out of what?

Quote from tristancliffe :

What would fall out of what?

It would fall down to the Earth ground, so blue one

Oh wait I understand now. lol

In theory it should be the red one if you could provide enough force to stop it sagging under its own weight. But then there would be so much force it would probably break

What am I thinking!?!?!? Sagging under its own weight... Weight is towards the centre of the earth (ignoring other celestial bodies), so if you have a bit of string long enough it'll just lie on the surface of the earth by gravity anyway.

For some reason (I'm knackered - racing at the weekend, 5-a-side last night, and I've just driven for 7 hours to collect a couple of tonnes of engine parts that I had to manually lift into a lorry (with the help of my brother I admit) I looked at the diagram, and used the old assumption that gravity is downwards. What a moron.

I dont even understand how it could be the red one, so i voted for blue.
Surely if i was to do this on a smaller scale, and just put some string around a small globe light thing, then the string would touch the whole way around. So why would it magically float?

Quote from Migz :

I dont even understand how it could be the red one, so i voted for blue.
Surely if i was to do this on a smaller scale, and just put some string around a small globe light thing, then the string would touch the whole way around. So why would it magically float?

Quote from mcintyrej :

if you pulled this string tight,

I think this is the key point, which is why it shouldn't touch the ground. I really want someone to do this now...

Quote from Migz :

I dont even understand how it could be the red one, so i voted for blue.
Surely if i was to do this on a smaller scale, and just put some string around a small globe light thing, then the string would touch the whole way around. So why would it magically float?

Thats what I originally thought, then I thought what I posted, now I realise its actually what I thought in the first place. Put some string around a football and it'll touch the football

EDIT: @ Passo - if you pull it tight - it'll touch the ground anyway and you'll have a bit more in your hands at the top

I think that the main problem is that most of us imagine it on Earth. But the sphere itself is the Earth, so the gravity is forcing the string to the centre of the sphere, so definitely blue one.

Damn it! :doh:

If its easier - think of a Bandana around your head. Pull it tight and you have more in your hands and it touches your head

WLSIT?!

*What lerts shit is this?


edit. It will touch the surface in both cases, if we presume the earth is perfectly smooth so it doesn't hang in air.

Quote from J@tko :

If its easier - think of a Bandana around your head. Pull it tight and you have more in your hands and it touches your head

Put a big magnet in your mouth and circle a metal wire around your head. And pull the wire.

But will it blend?

While in this case, I believe the group consensus of blue is correct, you shouldn't go just on the group consensus for facts that can be proved through math / physics.

For instance, I got in a big argument the other day about what color was created when yellow and green are mixed. My friends kept insisting that blue was created. After asking about 10 random strangers, and receiving the answer blue every time, i was in fits of rage over the ignorance of the general population.

Red, cause I like the color red

Yellow + Blue = Green, and it's likely this is what they were thinking of.

Blue wire. Gravity pulls it "down" and the pulling force on both ends will make it adhere to earths surface.