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over much greater distances than is possible today. The problem is that the metallic superconductors need to be so cold that they are not practical for transmission lines. There are new high temperature superconducting materials. They were discovered in 1986 by Karl Müller (1927-) and Johannes Bednorz (1950-). They were awarded the Nobel Prize in Physics in 1987 “for their important break-through in the discovery of superconductivity in ceramic materials.” To date, superconductivity in these ceramic materials is not understood theoretically. Such materials can be superconducting at temperatures as high as 138° K. This temperature is high enough to make many applications practical. Because the high temperature superconductors are ceramic, the materials cannot be formed into wire as metals can. However, future advances may produce usable high temperature superconductivity, which will revolutionize power transmission and other fields of electronics.

20

Think Quantum

WHEN A PARENT HOLDS A TODDLER and points to the moon saying “that’s the moon,” the toddler certainly has an awareness of the bright object in the sky. The toddler may learn that the light in the sky is called “moon,” but has no understanding of what and where the moon is. By the time a child is seven or eight, understanding of the moon has grown considerably. The child knows that it is very different from the street light at the end of the block, that it is very far away, and that you cannot touch the moon or even go there, although many years ago people actually did go to the moon. As an adult, a person has a good understanding of what the moon is even without knowing how to use Newton’s classical mechanics to calculate its orbit around the Earth. The adult knows that the moon’s apparent motion across the sky is caused by the rotation of the Earth, that the moon is far away, but not nearly as far as the planets in the solar system, and that a person feels much lighter and can jump higher on the moon than on Earth because the moon has less mass and, therefore, it exerts a weaker gravitational pull.

EXPERIENCE TEACHES US TO UNDERSTAND THE CLASSICAL WORLD

As we grow up, our increased understanding of the moon comes not just from education, but from the intuitive logic in the description of the moon in orbit around the Earth. This description is, in many respects, consistent with everyday experiences. If you throw a baseball, it arcs before falling back to Earth. If you throw the ball harder and aim higher, it goes higher and farther, making a bigger arc before hitting the ground. It is a simple and reasonable extension to accept that if you use a rocket and get an object moving really fast, aiming very high, you can make the arc extend halfway around the Earth, which is the basis for intercontinental missiles. After that, it is not a great leap to accept that if you use an even bigger rocket and get an object going even faster, the object will have an arc that is more or less a circle going around the Earth in orbit. Then the moon is just a very large object moving very fast so that it is in orbit around the Earth.

The fact that we can progress from a baseball to the moon orbiting the Earth is based on everyday classical mechanics experiences. However, it does require abstract reasoning to put the pieces together. The ancients reasonably thought that the moon circled the Earth. After all, you can see it move across the sky. We can do a simple experiment to see why the moon appears to circle the Earth. Standing in the middle of a room with a single light on a wall, if you slowly spin around, you will see the light come and go. With your back to the light, you do not see it. As you rotate, the light will come into the edge of your vision, move to the center of your view, and then disappear at the other edge of your view. It does not appear again until you have made a half circle of your rotation. Given this simple experience combined with what we know about baseballs and intercontinental missiles, it is easy to accept and, in fact, understand that