Tuesday, September 23, 2008

What is "scientific" about a magnet ?

The development of new magnetic materials is more engineering than science.

The science is in the study of the magnetic field, and how it interacts with everything else in the universe.

In fact, the first scientific paper was written about magnets.

This paper was written in the year 1269 by "Petrus Peregrinus" (Pierre de Maricourt) in a letter to his friend. In this paper, the writer summed up his lifetime of research into magnets. He also described the invention of the modern compass, a new astrolabe design, and a magnet powered motor.
He described how to magnetize steel, how to identify the poles of a magnet, how magnets will attract and repel each other, and other properties of lodestones and magnetized steel. He used spherical lodestones that he called Terellas "little Earths"

This letter was published, and translated into several languages, including English in the year 1271.

And then the plague arrived in Western Europe, and progress ground to a halt for more than 300 years. In the year 1600 William Gilbert, who had studied the published letters of Petrius Perigrinus de Maricourt, wrote the first intentional scientific book. It also was on the properties of the magnet, but it also included descriptions of the Earth's magnetic field, and similarities between magnetic and electrostatic attraction. Gilbert was the first to declare the planet Earth to be a magnet.

Gilbert was a Doctor, and the physician to the Queen of England. His home became the meeting place for the best minds of England at the time, and this group soon became "The Royal Society" that was formed to research, write, review, and publish scientific papers.

So the study of the magnet was the very beginning of modern science.


Black Diamond ??

It is unfortunate that the human race was not born knowing everything. All that is known by mankind has been learned a bit at a time.

A fine example of this is that we call the black center of a pencil "the Lead". This is because in the 18th century even the greatest scientists did not know that it was a form of carbon called graphite, and not a compound of lead. Even today, many people do not know that graphite and diamond are chemically identical.

And that brings us to "black diamond". Diamonds come in many colors, the transparent diamonds of any color have significant value. The black diamonds are commonly called industrial diamonds, and do not have the value of the transparent stones. Black diamonds are used in drill bits to cut through rock, or may be ground into cutting tools for the machining of metals.

There is another naturally occurring substance that is sometimes called "black diamond". It is an oxide of Iron called "gamma Hematite". It is readily found around Mount Vesuvius in Italy, a still active volcano, and carved by local craftsmen into jewlery.

And now, as you may have guessed, most hematites are magnetic. This fine black hematite can be magnetized into a fairly strong magnet. It is often ground into oval or spherical shapes and sold as "Rattlesnake eggs".

These hematite "eggs", being as hard and smooth as glass, will bounce off of each other when allowed to collide under their magnetic attraction, and then be pulled back together to collide again and again.
This rattle is the source of the name "rattlesnake eggs".

If you are so inclined, they can also be cut and ground into jewlery.

Monday, September 15, 2008

What should I not do with a magnet ?

The most important thing to avoid doing with a strong magnet, is letting it out of your sight.
This is for several reasons.
You do not want babies picking them up and putting them in their mouth, this is very bad !
You do not want to forget about them and walk away. They might stick to anything that passes nearby. (they love vacuum cleaners)
If you carelessly move another magnet nearby, the two may attract each other and collide with great violence. (I have shattered many Neodymium magnets this way)

Another thing NOT to do is underestimate it's power.
While carefully lowering a magnet towards a heavy steel plate, the plate may lift up to the magnet. Always immobilize a magnetic plate that a magnet will approach.

Another No-No depends on the strength of the magnets and how much you value your fingers. The crushing force between two magnets can be as strong as a hammer-blow.

If a second magnet or a piece of steel are "stuck hard" to a strong magnet, the most successful separation technique is to slide them apart. This may require using the edge of a non-magnetic tabletop to block one while the other is slid over the top.

Be careful that the separated magnets do not re-attract. Grab the second magnet or item before they separate.

Do not bring a magnet too near a color TV screen (CRT type). It can cause a strange shift in the displayed colors. If this happens, the screen needs to be "degaussed". Sometimes several degaussing passes are required.

If carrying a strong magnet from place to place. be aware of objects that may be attracted to it along the route.

And lastly, keep them clear of valuable magnetic recordings, such as VCR tapes, audio tapes, "floppy disks" , and credit cards.

Monday, August 25, 2008

Bocce, anyone ?

Bocce is a lawn bowling game from Renaissance Italy.

Modern Bocce sets have eight large balls, in two different colors. The balls of the same color are differentiated by two different patterns of engraved lines, allowing four players with two balls each. A team with red balls, and a team with green balls.

These balls are slightly larger than softballs, but are very hard and quite heavy. Modern balls are made from dense and hard plastic, such as phenolic. In the older days they would have been made from carved and polished stone of differing colors.

As Billiard players bring their own cue-sticks, Bocce players could bring their own Bocce balls.
There is also a small white ball, similar in size to a golf ball. This ball is internally weighted to make it heavy also. Typically it would have an Iron center-weight.
The play of the game is that someone would toss the white ball several yards in a random direction. Then the players would take turns bowling their large balls nearer to the white ball than any of the opponents balls. At the end of a round, the nearest ball would score a point, and all balls of the same color that are nearer to the white ball than the closest ball of the other color, will also score. Then the white ball will be tossed again to start another round.

At the time this game was invented, lodestones (spelled "loadstones" at that time) were laboratory curiosities. The common practice was to have them ground into perfect spheres, and engrave them with latitude and longitude marks aligned to the magnetic poles, to emulate the planet Earth.

Would a Bocce cheater have used his lodestones for Bocce balls, which could attract the white ball, and the player's other lodestone balls, to cheat?

Are there other ways to make a magnet float ?

Yes, there are other methods of making a magnet float.

Floating a magnet is one way to indicate that a substance has become super-conductive. A super-conductive substance provides absolutely no electrical resistance. When a magnet is brought nearby, an electrical current is generated in the superconductor. This electrical current will generate an electromagnetic field of it's own, and always opposing the original magnet. As the magnet comes closer the reverse field becomes stronger, and eventually it will float on the repelling field.
Since this process has no losses, the magnet will float for as long as the super-conductivity remains.

Another way is by utilizing the repulsion between similar poles of two magnets.
The trick is to prevent the floating magnet from flipping over and attracting the base magnet. The Levitron, from Edmund Scientific, spins the floating magnet like a top. The gyroscopic forces keep it from flipping until the rotation becomes too slow, which can take many minutes.

There are also "floating globes".
These devices float a hollow Iron sphere below an electromagnet. There is a sensor, usually optical, that continuously adjusts the power supplied to the electromagnet to maintain a constant float height.
The sphere will float for as long as adequate power is supplied.
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