The Compass

  • 8 Replies
  • 3109 Views
?

REPINSHAT

  • 12
  • +0/-0
The Compass
« on: May 06, 2006, 05:02:50 PM »
Note to moderators  Please do not delete my thread!  I am asking a fair and honest question and backing up my end of it and i ask that you kindly do the same :D


With a flat earth how do you explain how a compass works?

Here is how it works with a round earth.

A compass is an extremely simple device. A magnetic compass (as opposed to a gyroscopic compass) consists of a small, lightweight magnet balanced on a nearly frictionless pivot point. The magnet is generally called a needle. One end of the needle is often marked "N," for north, or colored in some way to indicate that it points toward north. On the surface, that's all there is to a compass.

 
The reason why a compass works is more interesting. It turns out that you can think of the Earth as having a gigantic bar magnet buried inside. In order for the north end of the compass to point toward the North Pole, you have to assume that the buried bar magnet has its south end at the North Pole, as shown in the diagram at the right. If you think of the world this way, then you can see that the normal "opposites attract" rule of magnets would cause the north end of the compass needle to point toward the south end of the buried bar magnet. So the compass points toward the North Pole.

To be completely accurate, the bar magnet does not run exactly along the Earth's rotational axis. It is skewed slightly off center. This skew is called the declination, and most good maps indicate what the declination is in different areas (since it changes a little depending on where you are on the planet).

The magnetic field of the Earth is fairly weak on the surface. After all, the planet Earth is almost 8,000 miles in diameter, so the magnetic field has to travel a long way to affect your compass. That is why a compass needs to have a lightweight magnet and a frictionless bearing. Otherwise, there just isn't enough strength in the Earth's magnetic field to turn the needle.


 


The "big bar magnet buried in the core" analogy works to explain why the Earth has a magnetic field, but obviously that is not what is really happening. So what is really happening?

No one knows for sure, but there is a working theory currently making the rounds. As seen on the above, the Earth's core is thought to consist largely of molten iron (red). But at the very core, the pressure is so great that this superhot iron crystallizes into a solid. Convection caused by heat radiating from the core, along with the rotation of the Earth, causes the liquid iron to move in a rotational pattern. It is believed that these rotational forces in the liquid iron layer lead to weak magnetic forces around the axis of spin.

It turns out that because the Earth's magnetic field is so weak, a compass is nothing but a detector for very slight magnetic fields created by anything.
if it has more than 3 moving parts I'm not interested"

?

REPINSHAT

  • 12
  • +0/-0
The Compass
« Reply #1 on: May 06, 2006, 05:11:09 PM »
Anyone?
if it has more than 3 moving parts I'm not interested"

?

ROTARY

The Compass
« Reply #2 on: May 06, 2006, 05:12:03 PM »
eerrr there are only 4 people logged on right now....

?

Unimportant

  • 1229
  • +0/-0
The Compass
« Reply #3 on: May 06, 2006, 06:06:47 PM »
Maybe there's a monopole magnet at the center of the earth. That would work.

?

Erasmus

  • The Elder Ones
  • 4242
  • +0/-0
The Compass
« Reply #4 on: May 06, 2006, 08:11:51 PM »
How do you feel about this suggestion?

-Erasmus
Why did the chicken cross the Möbius strip?

*

Don Carnage

  • 34
  • +0/-0
The Compass
« Reply #5 on: May 06, 2006, 09:36:36 PM »
Yar! I do be able to tell ye that the compass is a TRUE and LEGIT item. It do only work with this round earth, contrary to the Cuber belief of a cubic earth!
Yoho Yoho a pirate's life for me!
We pillage we plunder we rifle we loot, drink up me hearties yoho!
We kidnap and ravage and dont give a hoot, drink up me hearties yoho!
Yoho Yoho a pirate's life for me!

?

turin

  • 28
  • +0/-0
The Compass
« Reply #6 on: May 06, 2006, 09:53:09 PM »
The functionality of a compass does not require direct physical access to the geographic locations of the magnetic poles.  According to contemporary (and in fact quite well established) laws of electromagnetism (specifically Gauss' and Ampere's Laws), the magnetic field should influence a compass needle (being itself a magnetic dipole) to point towards a given magnetic pole regardless of the existence of a counter pole.  The location of the counterpole, if it does indeed exist, only serves to adjust or reinforce the pointing of the compass.
ffiliation:  undecided

?

REPINSHAT

  • 12
  • +0/-0
The Compass
« Reply #7 on: May 07, 2006, 06:48:15 AM »
Quote from: "Erasmus"
How do you feel about this suggestion?

-Erasmus


While interesting I cannot see how more than one magnet can co-exist with one another?
if it has more than 3 moving parts I'm not interested"

?

Erasmus

  • The Elder Ones
  • 4242
  • +0/-0
The Compass
« Reply #8 on: May 07, 2006, 09:32:04 AM »
Quote from: "REPINSHAT"
While interesting I cannot see how more than one magnet can co-exist with one another?


Strange... my refrigerator seems to have no trouble at all supporting two co-existing magnets...

-Erasmus
Why did the chicken cross the Möbius strip?