11. Work in groups. Group 1 summarize everything that you know about

semiconductors. Group 2 the same about computers.

11. Give interesting facts that you know in the sphere of physics, electronics, mathematics etc. Your group mate will act as an interpreter from Russian into English.

Divide into 2 groups. Group A translates text A group B translates text B “Communicating Through the Earth” with a dictionary.

Text A

Communicating Through the Earth

part I

How do we communicate with people beyond the horizon? What can be made to follow the curve of earth's surface?

Of course, we can send electrical signals through wires around any curves. In the Nineteenth Century, copper wires were strung across the continents and ocean floors and the world was united through te­legraphy. That takes a lot of copper, though, and a lot of maintenance.

We could send light-wave signals and do away with wires, but light waves move in a straight line and won't curve around the earth's bulge. We would have to set up relay stations or place mirrors in orbit to make that work.

Radio waves, like light waves but a million times longer, do better. They travel in straight lines, too, but the upper atmosphere contains regions rich in charged particles (the ionosphere) that tend to reflect the radio waves. It is as though there were natural mirrors in the sky. That makes it possible to send radio signals long distances, and in the Twentieth Century the world was united without wires.

However, the ionosphere is affected by the solar wind. When the sun produces flares, an electrical storm can take place that will disrupt radio communications.

But short radio waves (microwaves) can go right through the ionosphere and be amplified and sent on by communications satellites. As communications satellites improve, signals will be sent from place to place on earth with so little trouble that it would seem unreasonable to ask for anything better.

What can go through the earth itself? Light certainly can't. Radio waves can't. We can't even string wires through the earth to carry electrical signals.

One thing that does travel through the body of the earth is an earthquake wave, but it takes a very hard blow to set the earth to vibrat­ing perceptibly.

Text b Communicating Through the Earth part II

On the other hand, certain massless subatomic particles called neutrinos travel at the speed of light and go through matter as though it weren't there. A beam of neutrinos could travel through trillions of miles of solid lead and come out the other end just about unaffected. Neutrinos reach us from every direction and almost every neutrino that does so passes right through the earth in less than a 20th of a second (and through us if we are in their paths).

This doesn't mean that neutrinos can't be detected. Out of many trillions, one neutrino may occasionally combine with an atomic nucleus and induce a detectable change.

Thus, huge vats of cleaning fluid made up of molecules that include chlorine atoms can serve as a “neutrino telescope”. Such neutri­no telescopes can be placed in mines, a couple of miles under the earth's crust. In that case, nothing can reach them but neutrinos, and, in this way, neutrino-producing reactions deep in the sun's соrе can be studied.

Scientists can produce neutrino beams without much trouble. Some day it might be possible to send them out in Morse code or in more complicated modulation. The day may come when improved neutrino telescopes, using water rather than cleaning fluid, will be placed all over the earth, eventually television sets might be built that would incorporate the equivalent of neutrino telescopes and convert the signals directly into sight and sound.

If this could be done, communications satellites would be un­necessary and so would relay stations of any sort. Any two points on earth's surface (or in mines, or under the sea) would be connected by a mathematically straight line along which neutrinos would move at the speed of light. There is no way of communicating more quickly.

For that matter, neutrinos move in a straight line throughout the universe. They are unaffected by the electromagnetic fields and dust clouds that can disrupt or block microwaves and light.

In the end, then, it may be that communications among worlds would be carried out through neutrino beams.

Perhaps that is why we aren't detecting signals from other intelligent civilizations out there. We're looking for beams of micro­waves, but perhaps we should be looking for beams of neutrinos.