>> ^Ornthoron:

>> ^deathcow:
I put a big aluminum bar directly in one once, and got to move it around... its weird. Even aluminum responds.

Not in the same way as iron, though. Aluminum is not ferromagnetic, and is therefore not attracted to the MRI magnet. But if you move it around in the magnetic field you will induce an electrical current in the aluminum. This electrical current sets up its own small magnetic field, and it's this new field's interaction with the field from the MRI that you can feel when you move the bar around. The interaction stops as soon as you hold the bar still again.


Awesome reply. Your science embiggens my mind.

>> ^Ornthoron:

>> ^deathcow:
I put a big aluminum bar directly in one once, and got to move it around... its weird. Even aluminum responds.

Not in the same way as iron, though. Aluminum is not ferromagnetic, and is therefore not attracted to the MRI magnet. But if you move it around in the magnetic field you will induce an electrical current in the aluminum. This electrical current sets up its own small magnetic field, and it's this new field's interaction with the field from the MRI that you can feel when you move the bar around. The interaction stops as soon as you hold the bar still again.


Thanks! interesting.

>> ^deathcow:

I put a big aluminum bar directly in one once, and got to move it around... its weird. Even aluminum responds.

Not in the same way as iron, though. Aluminum is not ferromagnetic, and is therefore not attracted to the MRI magnet. But if you move it around in the magnetic field you will induce an electrical current in the aluminum. This electrical current sets up its own small magnetic field, and it's this new field's interaction with the field from the MRI that you can feel when you move the bar around. The interaction stops as soon as you hold the bar still again.

>> ^charliem:

Idea!
Launch a satellite that's one gigantic electromagnet, leave it in orbit for 30 years...no more space junk!

Good thinking! But aluminium, which most spacecraft and thus also space junk are made of, is sadly not ferromagnetic, so the electromagnet would have no effect.

^Well, not all metals are magnetic. Aluminium, which was used in this experiment, is paramagnetic. Paramagnetic materials typically couple quite weakly to magnetic fields, so I don't think there was any chance of the block causing harm, as opposed to this ferromagnetic object.

The reason it falls slowly is that it moves through a magnetic field, which induces a current in the metal. This current sets up its own magnetic field with opposite polarity to the external field.

A ferromagnetic bottle is brought near the bore of the super high strength magnet of an MRI machine and is sucked in, oscillating violently in midair. Sadly, this very type of incident did in fact kill someone a few years back. http://www.radiologytoday.net/archive/rt_103105p2.shtml