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Old October 25 2009, 09:18 PM   #1
All Seeing Eye
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Earths Magnetic Field

If you built a huge electro-magnet in space around Earth (let's say above the north pole) and switched it on, would the Earth's North point of its magnetic field repel the North point of the magnetic field of the large electro-magnet, pushing it away?

Why does the Earths magnetic field not interact with the Suns magnetic fields? causing a pushing and pulling effect?
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Old October 25 2009, 09:32 PM   #2
Chaos Descending
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Re: Earths Magnetic Field

I Am Legend wrote: View Post
If you built a huge electro-magnet in space around Earth (let's say above the north pole) and switched it on, would the Earth's North point of its magnetic field repel the North point of the magnetic field of the large electro-magnet, pushing it away?
Yes. It would in fact try to flip the electromagnet around so the south pole of the magnet is pointing at the north pole of the Earth.

FYI, that's how a COMPASS works.

Why does the Earths magnetic field not interact with the Suns magnetic fields? causing a pushing and pulling effect?
Why do you think it doesn't? Earth's south pole is attracted to the Sun's north pole, and repelled by the Sun's south pole. Likewise, Earth's north pole is attracted to the Sun's south pole and repelled by it's north pole. Since each have a north and a south, and 93 million miles separates the two, the net effect is basically negligible.

Hold two fridge magnets 10 feet away from each other and see how much influence they have on one another.
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Old October 25 2009, 09:36 PM   #3
Asbo Zaprudder
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Re: Earths Magnetic Field

I Am Legend wrote: View Post
If you built a huge electro-magnet in space around Earth (let's say above the north pole) and switched it on, would the Earth's North point of its magnetic field repel the North point of the magnetic field of the large electro-magnet, pushing it away?

Why does the Earths magnetic field not interact with the Suns magnetic fields? causing a pushing and pulling effect?
1) Yes initially, but the electromagnet would want to flip over and crash into the Earth. You'd need to stabilise it. You can see this effect easily with 2 bar magnets.

2) That carves out the Magnetosphere, leads to magnetic interaction and causes geomagnetic storms. About 100+ GW of power can be dumped into the Magnetosphere if the solar wind's magnetic field is directed southward. I 've never seen a calculation for the mechanical effect on the Earth. I suspect it's tiny.
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Old October 25 2009, 10:17 PM   #4
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Re: Earths Magnetic Field

Item First: You said no new posts here. What changed?

Item Second: It depends on the mass and field strength of your magnet. It could be as insignificant as nothing, right up to getting your eye shot out at incredible velocity!
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Old October 25 2009, 10:31 PM   #5
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Re: Earths Magnetic Field

Great Mambo Chicken wrote: View Post

1) Yes initially, but the electromagnet would want to flip over and crash into the Earth. You'd need to stabilise it. You can see this effect easily with 2 bar magnets.
Well let's say hypothetically speaking it was possible to stabilise it so it wouldn't flip, would the electro-magnet be repelled away at a large velocity?
I'm assuming the velocity would be quite great due to the immense size of the Earths Magnetic field??

Last edited by All Seeing Eye; October 25 2009 at 10:44 PM.
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Old October 25 2009, 10:38 PM   #6
Chaos Descending
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Re: Earths Magnetic Field

I Am Legend wrote: View Post
Great Mambo Chicken wrote: View Post

1) Yes initially, but the electromagnet would want to flip over and crash into the Earth. You'd need to stabilise it. You can see this effect easily with 2 bar magnets.
Well let's say hypothetically speaking it was possible to stabilise it so it wouldn't flip, would the electro-magnet would be repelled away at a large velocity?
I'm assuming the velocity would be quite great due to the immense size of the Earths EM field??
That depends on how much mass it has. The more mass it has, the more gravity will pull it down toward Earth. The EM force of the magnet would have to be extra-strong to overcome gravity.

Your assumption that it would fling away "at a large velocity" is completely groundless. It all depends on the net difference between the attractive force of gravity and the repulsive force of magnetism, as well as the mass of the magnet. More massive = slower. Besides, the velocity is irrelevant. Initially the velocity would be zero, but increasing. You meant to imply acceleration, which is the rate at which velocity changes.
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Old October 26 2009, 10:03 AM   #7
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Re: Earths Magnetic Field

Chaos Descending wrote: View Post
I Am Legend wrote: View Post
If you built a huge electro-magnet in space around Earth (let's say above the north pole) and switched it on, would the Earth's North point of its magnetic field repel the North point of the magnetic field of the large electro-magnet, pushing it away?
Yes. It would in fact try to flip the electromagnet around so the south pole of the magnet is pointing at the north pole of the Earth.

FYI, that's how a COMPASS works.

Why does the Earths magnetic field not interact with the Suns magnetic fields? causing a pushing and pulling effect?
Why do you think it doesn't? Earth's south pole is attracted to the Sun's north pole, and repelled by the Sun's south pole. Likewise, Earth's north pole is attracted to the Sun's south pole and repelled by it's north pole. Since each have a north and a south, and 93 million miles separates the two, the net effect is basically negligible.

Hold two fridge magnets 10 feet away from each other and see how much influence they have on one another.
Apologies for any errors in my barely-there-knowledge of about the sun.

But does it actually have a "north" and "south" pole? Well, I'm pretty sure it has poles that are north and south, but I believe I remember from a documentary that the sun's electromagnetic field is extremely complex and continually changing with a hell of a lot more poles than one might assume. Thousands of them actually.
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Old October 26 2009, 10:22 AM   #8
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Re: Earths Magnetic Field

Thingol wrote: View Post

Apologies for any errors in my barely-there-knowledge of about the sun.

But does it actually have a "north" and "south" pole? Well, I'm pretty sure it has poles that are north and south, but I believe I remember from a documentary that the sun's electromagnetic field is extremely complex and continually changing with a hell of a lot more poles than one might assume. Thousands of them actually.
It's magnetic field certainly does.
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Old October 26 2009, 04:21 PM   #9
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Re: Earths Magnetic Field

The Earths magnetic field exists at the Earths surface level and above, so if a large electro-magnet was built and turned on at the Earths surface why doesn't it attempt to flip??

If again hypothetically speaking it could be prevented from flipping would it be repelled upwards??

Seriously this is what confuses me most, the fact that magnets depending on whether you're in the northern or southern hemispheres don't try to flip and magnetise to the ground. They're all located in the Earths magnetic field and should therefore be attracted to it.
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Old October 26 2009, 04:43 PM   #10
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Re: Earths Magnetic Field

What a cool idea for a "Bond Villian super evil device", A large super conducting magnet powered by a mini nuclear reactor placed on the North pole to neutralize the earth's magnetic field so that solar wind can crash through and screw up the world's power grid, that is if he is not paid:

ONE TREEELLLION DOLLARS, MWAHAHAHAHAHAHA
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Old October 26 2009, 05:15 PM   #11
Asbo Zaprudder
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Re: Earths Magnetic Field

I Am Legend wrote: View Post
The Earths magnetic field exists at the Earths surface level and above, so if a large electro-magnet was built and turned on at the Earths surface why doesn't it attempt to flip??

If again hypothetically speaking it could be prevented from flipping would it be repelled upwards??

Seriously this is what confuses me most, the fact that magnets depending on whether you're in the northern or southern hemispheres don't try to flip and magnetise to the ground. They're all located in the Earths magnetic field and should therefore be attracted to it.
The force is tiny. Compass needles weigh bugger all. Large electromagnets are massive and usually bolted down.
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Old October 26 2009, 05:34 PM   #12
All Seeing Eye
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Re: Earths Magnetic Field

Great Mambo Chicken wrote: View Post
I Am Legend wrote: View Post
The Earths magnetic field exists at the Earths surface level and above, so if a large electro-magnet was built and turned on at the Earths surface why doesn't it attempt to flip??

If again hypothetically speaking it could be prevented from flipping would it be repelled upwards??

Seriously this is what confuses me most, the fact that magnets depending on whether you're in the northern or southern hemispheres don't try to flip and magnetise to the ground. They're all located in the Earths magnetic field and should therefore be attracted to it.
The force is tiny. Compass needles weigh bugger all. Large electromagnets are massive and usually bolted down.
So a ground based, none bolted, large enough electro-magnet would repel against the Earths magnetic field? if prevented from flipping it could hover or take off?
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Old October 26 2009, 06:04 PM   #13
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Re: Earths Magnetic Field

The weight would have to be small compared to the repulsive force. I don't think that's possible given present materials science.

However, substitute the Earths' magnetic field for a stronger one locally, and you have MagLev trains.
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Old October 26 2009, 06:39 PM   #14
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Re: Earths Magnetic Field

I Am Legend wrote: View Post
So a ground based, none bolted, large enough electro-magnet would repel against the Earths magnetic field? if prevented from flipping it could hover or take off?
Gyroscopes will prevent it flipping. But the magnet's weight is what prevents the kind of levitation you want to achieve.

You remember Force = Mass x Acceleration ?

To get levitation, you have to counter gravitational acceleration, which is when

Magnetic Repulsion Force / Mass of Magnet > Earth's Gravational Acceleration (a constant = 9.8ms^-2)

It's this ratio (Magnetic Repulsion Force / Mass of Magnet) which you'll struggle to get big enough.
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Old October 26 2009, 07:04 PM   #15
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Re: Earths Magnetic Field

The Earth's magnetic field is really weak so it wouldn't do anything. It's around 50 microteslas, about the same as a typical bar magnet. The reason that magnetic things aren't attracted to/repelled from the Earth is that the force of gravity is many orders of magnitude stronger.
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