Stories from Physics
The Magnet
I
In olden days there was a shepherd whose name was Magnes. Magnes lost a sheep. He went to the mountains to find it. He came to a place where there were barren rocks. He walked over these rocks, and felt that his boots were sticking to them. He touched them with his hand, but they were dry and did not stick to his hand. He started to walk again, and again his boots stuck to the rocks. He sat down, took off one of his boots, took it into his hand, and touched the rocks with it.
Whenever he touched them with his skin, or with the sole of his boot, they did not stick; but when he touched them with the nails, they did stick.
Magnes had a cane with an iron point.
He touched a rock with the wood; it did not stick; he touched it with the iron end, and it stuck so that he could not pull it off.
Magnes looked at the stone, and he saw that it looked like iron, and he took pieces of that stone home with him. Since then that rock has been known, and has been called Magnet.
II
Magnet is found in the earth with iron ore. Where there is magnet in the ore, the iron is of the best quality. The magnet resembles iron.
If you put a piece of iron on a magnet, the iron itself begins to attract other iron. And if you put a steel needle on a magnet, and hold it thus for awhile, the needle will become a magnet, and will attract iron. If two magnets are brought together at their ends, one side will turn away from the other, while the other sides will be attracted.
If a magnetic rod is broken in two, each half will attract at one end, and will turn away at the other end. Cut it again, and the same will happen; cut it again, as often as you please, and still the same will happen: equal ends will turn away from each other, while opposite ends will be attracted, as though the magnet were pushing away at one end, and pulling in at the other. No matter how you may break it, it will be as though there were a bump at one end, and a saucer at the other. Whichever way you put them together—a bump and a saucer will meet, but a bump and a bump, or a saucer and a saucer will not.
III
If you magnetize a needle (holding it for awhile over a magnet), and attach it in the middle to a pivot in such a way that it can move freely around, and let it loose, it will turn with one end toward midday (south), and with the other toward midnight (north).
When the magnet was not known, people did not sail far out to sea. When they went out far into the sea, so that land was not to be seen, they could tell only by the stars and the sun where they had to sail. But when it was dark, and the sun or stars could not be seen, they did not know which way to sail. And a ship was borne by the winds and carried on rocks and wrecked.
So long as the magnet was not known, they did not sail far from the shore; but when the magnet was discovered, they made a magnetic needle on a pivot, so that it should move around freely. By this needle they could tell in which direction to sail. With the magnetic needle they began to sail farther away from the shores, and since then they have discovered many new seas.
On ships there is always a magnetic needle (compass), and there is a measuring-rope with knots at the stern of a ship. This rope is fixed in such a way that when it unrolls, they can tell how far the ship has travelled. And thus, in sailing in a boat, they always know in what spot it is, whether far from the shore, and in what direction it is sailing.
Injurious Air
In the village of Nikólskoe, the people went on a holiday to mass. In the manor yard were left the cow-tender, the elder, and the groom. The cow-tender went to the well for water. The well was in the yard itself. She pulled out the bucket, but could not hold it. The bucket pulled away from her, struck the side of the well, and tore the rope. The cow-tender returned to the hut and said to the elder:
“Aleksándr! Climb down into the well—I have dropped the bucket into it.”
Aleksándr said:
“You have dropped it, so climb down yourself.”
The cow-tender said that she did not mind fetching it herself, if he would let her down.
The elder laughed at her, and said:
“Well, let us go! You have an empty stomach now, so I shall be able to hold you up, for after dinner I could not do it.”
The elder tied a stick to a rope, and the woman sat astride it, took hold of the rope, and began to climb down into the well, while the elder turned the well-wheel. The well was about twenty feet deep, and there was less than three feet of water in it. The elder let her down slowly, and kept asking:
“A little more?”
And the cow-tender cried from below:
“Just a little more!”
Suddenly the elder felt the rope give way: he called the cow-tender, but she did not answer. The elder looked into the well, and saw the cow-tender lying with her head in the water, and with her feet in the air. The elder called for help, but there was nobody nearby; only the groom came. The elder told him to hold the wheel, and he himself pulled out the rope, sat down on the stick, and went down into the well.
The moment the groom let the elder down to the water, the same thing happened to the elder. He let go of the rope and fell head foremost upon the woman. The groom began to cry, and ran to church to call the people. Mass was over, and people were walking home. All the men and women rushed to the well. They gathered around it, and everybody holloaed, but nobody knew what to do. The young carpenter Iván made his way through the crowd, took hold of the rope, sat down on the stick, and told them to let him down. Iván tied himself to the rope with his belt. Two men let him down, and the rest looked into the well, to see what would become of Iván. Just as he was getting near the water, he dropped his hands from the rope, and would have fallen down head foremost, if the belt had not held him. All shouted, “Pull him out!” and Iván was pulled out.
He hung like dead down from the belt, and his head was drooping and beating against the sides of the well. His face was livid. They took him off the rope and put him down on the ground. They thought that he was dead; but he suddenly drew a deep breath, began to rattle, and soon revived.
Others wanted to climb down, but an old peasant said that they could not go down because there was bad air in the well, and that that bad air killed people. Then the peasants ran for hooks and began to pull out the elder and the woman. The elder’s mother and wife cried at the well, and others tried to quiet them; in the meantime the peasants put down the hooks and tried to get out the dead people. Twice they got the elder halfway up by his clothes; but he was heavy, and his clothes tore and he fell down. Finally they stuck two hooks into him and pulled him out. Then they pulled out the cow-tender. Both were dead and did not revive.
Then, when they examined the well, they found that indeed there was bad air down in the well.
This air is so heavy that neither man nor any animal can live in it. They let down a cat into the well, and the moment she reached the place where the bad air was, she died. Not only can no animal live there, even no candle will burn in it. They let down a candle, and the moment it reached that spot, it went out.
There are places underground where that air gathers, and when a person gets into one of those places, he dies at once. For this purpose they have lamps in the mines, and before a man goes down to such a place, they let down the lamp. If it goes out, no man can go there; then they let down fresh air until the lamp will burn.
Near the city of Naples there is one such cave. There is always about three feet of bad air in it on the ground, but above it the air is good. A man can walk through the cave, and nothing will happen to him, but a dog will die the moment it enters.
Where does this bad air come from? It is made of the same good air that we breathe. If you gather a lot of people in one place, and close all the doors and windows, so that no fresh air can get in, you will get the same kind of an air as in the well, and people will die.
One hundred years ago, during a war, the Hindus captured 146 Englishmen and shut them up in a cave underground, where the air could not get in.
After the captured Englishmen had been there a few hours they began to die, and toward the end of the night 123 had died, and the rest came out more dead than alive, and ailing. At first the air had been good in the cave; but when the captives had inhaled all the good air, and no fresh air came in, it became bad, just like what was in the well, and they died.
Why does the good air become bad when many people come together?
Because, when people breathe, they take in good air and breathe out bad air.
Galvanism
There was once a learned Italian, Galvani. He had an electric machine, and he showed his students what electricity was. He rubbed the glass hard with silk with something smeared over it, and then he approached to the glass a brass knob which was attached to the glass, and a spark flew across from the glass to the brass knob. He explained to them that the same kind of a spark came from sealing-wax and amber. He showed them that feathers and bits of paper were now attracted, and now repelled, by electricity, and explained to them the reason of it. He did all kinds of experiments with electricity, and showed them all to his students.
Once his wife grew ill. He called a doctor and asked him how to cure her. The doctor told him to prepare a frog soup for her. Galvani gave order to have edible frogs caught. They caught them for him, killed them, and left them on his table.
Before the cook came after the frogs, Galvani kept on showing the electric machine to his students, and sending sparks through it.
Suddenly he saw the dead frogs jerk their legs on the table. He watched them, and saw that every time when he sent a spark through the machine, the frogs jerked their legs. Galvani collected more frogs, and began to experiment with them. And every time he sent a spark through the machine, the dead frogs moved their legs as though they were alive.
It occurred to Galvani that live frogs moved their legs because electricity passed through them. Galvani knew that there was electricity in the air; that it was more noticeable in the amber and glass, but that it was also in the air, and that thunder and lightning came from the electricity in the air.
So he tried to discover whether the dead frogs would not move their legs from the electricity in the air. For this purpose he took the frogs, skinned them, chopped off their heads, and hung them on brass hooks on the roof, beneath an iron gutter. He thought that as soon as there should be a storm, and the air should be filled with electricity, it would pass by the brass rod to the frogs, and they would begin to move.
But the storm passed several times, and the frogs did not move. Galvani was just taking them down, and as he did so a frog’s leg touched the iron gutter, and it jerked. Galvani took down the frogs and made the following experiment: he tied to the brass hook an iron wire, and touched the leg with the wire, and it jerked.
So Galvani decided that the animals lived because there was electricity in them, and that the electricity jumped from the brain to the flesh, and that made the animals move. Nobody had at that time tried this matter and they did not know any better, and so they all believed Galvani. But at that time another learned man, Volta, experimented in his own way, and proved to everybody that Galvani was mistaken. He tried touching the frog differently from what Galvani had done, not with a copper hook with an iron wire, but either with a copper hook and a copper wire, or an iron hook and an iron wire—and the frogs did not move. The frogs moved only when Volta touched them with an iron wire that was connected with a copper wire.
Volta thought that the electricity was not in the dead frog but in the iron and copper. He experimented and found it to be so: whenever he brought together the iron and the copper, there was electricity; and this electricity made the dead frogs jerk their legs. Volta tried to produce electricity differently from what it had been produced before. Before that they used to get electricity by rubbing glass or sealing-wax. But Volta got electricity by uniting iron and copper. He tried to connect iron and copper and other metals, and by the mere combination of metals, silver, platinum, zinc, lead, iron, he produced electric sparks.
After Volta they tried to increase electricity by pouring all kinds of liquids—water and acids—between the metals. These liquids made the electricity more powerful, so that it was no longer necessary, as before, to rub in order to produce it; it is enough to put pieces of several metals in a bowl and fill it with a liquid, and there will be electricity in that bowl, and the sparks will come from the wires.
When this kind of electricity was discovered, people began to apply it: they invented a way of gold and silver plating by means of electricity, and electric light, and a way to transmit signs from place to place over a long distance by means of electricity.
For this purpose pieces of different metals are placed in jars, and liquids are poured into them. Electricity is collected in these jars, and is transferred by means of wires to the place where it is wanted, and from that place the wire is put into the ground. The electricity runs through the ground back to the jars, and rises from the earth by means of the other wire; thus the electricity keeps going around and around, as in a ring—from the wire into the ground, and along the ground, and up the wire, and again through the earth. Electricity can travel in either direction, just as one wants to send it: it can first go along the wire and return through the earth, or first go through the earth, and then return through the wire. Above the wire, in the place where the signs are given, there is attached a magnetic hand, and that hand turns in one direction, when the electricity is allowed to pass through the wire and back through the earth, and in another direction, when the electricity is sent through the earth and back through the wire. Along this hand there are certain signs, and by means of these signs they write from one place to another on the telegraph.
The Sun’s Heat
Go out in the winter on a calm, frosty day into the field, or into the woods, and look about you and listen: all around you is snow, the rivers are frozen, dry grass blades stick out of the grass, the trees are bare—nothing is moving.
Look in the summer: the rivers are running and rippling, in every puddle the frogs croak and plunge in; the birds fly from place to place, and whistle, and sing; the flies and the gnats whirl around and buzz; the trees and the grass grow and wave to and fro.
Freeze a pot with water, and it will become as hard as a rock. Put the frozen pot on the fire: the ice will begin to break, and melt, and move; the water will begin to stir, and bubbles will rise; then, when it begins to boil, it whirls about and makes a noise. The same happens in the world from the heat. Without heat everything is dead; with the heat everything moves and lives. If there is little heat, there is little motion; with more heat, there is more motion; with much heat, there is much motion; with very much heat, there is also very much motion.
Where does the heat in the world come from? The heat comes from the sun.
In winter the sun travels low, to one side, and its beams do not fall straight upon the earth, and nothing moves. The sun begins to travel higher above our heads, and begins to shine straight down upon the earth, and everything is warmed up in the world, and begins to stir.
The snow settles down; the ice begins to melt on the rivers; the water comes down from the mountains; the vapours rise from the water to the clouds, and rain begins to fall. Who does it all?—The sun. The seeds swell, and let out rootlets; the rootlets take hold of the ground; old roots send up new shoots, and the trees and the grass begin to grow. Who has done that?—The sun.
The bears and moles get up; the flies and bees awaken; the gnats are hatched, and the fish come out from their eggs, when it is warm. Who has done it all?—The sun.
The air gets warmed up in one place, and rises, and in its place comes colder air—and there is a wind. Who has done that?—The sun.
The clouds rise and begin to gather and to scatter—and the lightning flashes. Who has made that fire?—The sun.
The grass, the grain, the fruits, the trees grow up; animals find their food, men eat their fill, and gather food and fuel for the winter; they build themselves houses, railways, cities. Who has prepared it all?—The sun.
A man has built himself a house. What has he made it of? Of timbers. The timbers were cut out of trees, but the trees are made to grow by the sun.
The stove is heated with wood. Who has made the wood to grow?—The sun.
Man eats bread, or potatoes. Who has made them grow?—The sun. Man eats meat. Who has made the animals, the birds to grow?—The grass. But the grass is made to grow by the sun.
A man builds himself a house from brick and lime. The bricks and the lime are burnt by wood. The wood has been prepared by the sun.
Everything that men need, that is for their use—all that is prepared by the sun, and on all that goes much sun’s heat. The reason that men need bread is because the sun has produced it, and because there is much sun’s heat in it. Bread warms him who eats it.
The reason that wood and logs are needed is because there is much heat in them. He who buys wood for the winter, buys sun’s heat; and in the winter he burns the wood whenever he wants it, and lets the sun’s heat into his room.
When there is heat, there is motion. No matter what motion it may be—it all comes from heat, either directly from the sun’s heat, or from the heat which the sun has prepared in the coal, the wood, the bread, and the grass.
Horses and oxen pull, men work—who moves them?—Heat. Where does the heat come from?—From the food. And the food has been prepared by the sun.
Watermills and windmills turn around and grind. Who moves them?—Wind and water. And who drives the wind?—Heat. And who drives the water?—Again heat. Heat raises the water in the shape of vapour, and without this the water would not be falling down. A machine works—it is moved by steam. And who makes steam?—Wood. And in the wood is the sun’s heat.
Heat makes motion, and motion makes heat. And both heat and motion are from the sun.