FORCE FIELDS 11
MAGNETIC LÉVITATION
In science fiction, force fields have another purpose besides deflecting
ray-gun blasts, and that is to serve as a platform to defy gravity. In the
movie Back to the Future, Michael J. Fox rides a "hover board," which
resembles a skateboard except that it floats over the street. Such an
antigravity device is impossible given the laws of physics as we know
them today (as we will see in Chapter 10). But magnetically enhanced
hover boards and hover cars could become a reality in the future, giving us the ability to levitate large objects at will. In the future, if "roomtemperature superconductors" become a reality, one might be able to
levitate objects using the power of magnetic force fields.
If we place two bar magnets next to each other with north poles
opposite each other, the two magnets repel each other. (If we rotate the
magnet, so that the north pole is close to the other south pole, then the
two magnets attract each other.) This same principle, that north poles
repel each other, can be used to lift enormous weights off the ground.
Already several nations are building advanced magnetic lévitation
trains (maglev trains) that hover just above the railroad tracks using
ordinary magnets. Because they have zero friction, they can attain
record-breaking speeds, floating over a cushion of air.
In 1984 the world's first commercial automated maglev system began operation in the United Kingdom, running from Birmingham International Airport to the nearby Birmingham International railway
station. Maglev trains have also been built in Germany, Japan, and Korea, although most of them have not been designed for high velocities.
The first commercial maglev train operating at high velocities is the
initial operating segment (IOS) demonstration line in Shanghai, which
travels at a top speed of 268 miles per hour. The Japanese maglev train
in Yamanashi prefecture attained a velocity of 361 miles per hour, even
faster than the usual wheeled trains.
But these maglev devices are extremely expensive. One way to increase efficiency would be to use superconductors, which lose all electrical resistance when they are cooled down to near absolute zero.
Superconductivity was discovered in 1911 by Heike Onnes. If certain
MAGNETIC LÉVITATION
In science fiction, force fields have another purpose besides deflecting
ray-gun blasts, and that is to serve as a platform to defy gravity. In the
movie Back to the Future, Michael J. Fox rides a "hover board," which
resembles a skateboard except that it floats over the street. Such an
antigravity device is impossible given the laws of physics as we know
them today (as we will see in Chapter 10). But magnetically enhanced
hover boards and hover cars could become a reality in the future, giving us the ability to levitate large objects at will. In the future, if "roomtemperature superconductors" become a reality, one might be able to
levitate objects using the power of magnetic force fields.
If we place two bar magnets next to each other with north poles
opposite each other, the two magnets repel each other. (If we rotate the
magnet, so that the north pole is close to the other south pole, then the
two magnets attract each other.) This same principle, that north poles
repel each other, can be used to lift enormous weights off the ground.
Already several nations are building advanced magnetic lévitation
trains (maglev trains) that hover just above the railroad tracks using
ordinary magnets. Because they have zero friction, they can attain
record-breaking speeds, floating over a cushion of air.
In 1984 the world's first commercial automated maglev system began operation in the United Kingdom, running from Birmingham International Airport to the nearby Birmingham International railway
station. Maglev trains have also been built in Germany, Japan, and Korea, although most of them have not been designed for high velocities.
The first commercial maglev train operating at high velocities is the
initial operating segment (IOS) demonstration line in Shanghai, which
travels at a top speed of 268 miles per hour. The Japanese maglev train
in Yamanashi prefecture attained a velocity of 361 miles per hour, even
faster than the usual wheeled trains.
But these maglev devices are extremely expensive. One way to increase efficiency would be to use superconductors, which lose all electrical resistance when they are cooled down to near absolute zero.
Superconductivity was discovered in 1911 by Heike Onnes. If certain