Everybody was very busy indeed for about half an hour. At the end of that time the twelve rough drawings were done and pinned up at equal distances apart around the walls of the playroom, three on each of the four walls. They were arranged around the room in the same order in which Uncle Henry had assigned them. The room then looked like this, though of course you see only three walls in a picture. You must imagine how the fourth wall looked.
“Now Paul, suppose you walk around the table again, spinning on your own axis as you go, and we’ll try to find out what the Zodiac is. You notice that the pictures are all pinned on the walls at the same height from the floor, which is just the height of the electric lamp bulb, and just the height of Paul’s head too, no matter where he is in his walk around the lamp. The twelve constellations, or signs of the Zodiac are in the real sky also on the same level with the earth and the sun, no matter where the earth is in its journey round the sun. Astronomers say it this way: they say that the earth revolves around the sun ‘in the plane of the ecliptic.’ That simply means that if the sun was in the centre of an enormous horizontal pane of glass, the earth and all the signs of the Zodiac would also always be touching the pane of glass, which would then represent the ‘plane of the ecliptic.’ Put an l in ‘pane’ and you have ‘plane.’”
“Is each sign for a month?” asked Peter. “I see there are twelve of them.”
“That’s correct,” said Uncle Henry, “and you want to notice that as Paul walks round the lamp and looks across it at the signs on the wall beyond it, the lamp seems to Paul to move from one picture to the next.”
This picture is drawn as if the ceiling of the room was taken off and you could look down on Paul walking around the lamp.
When it is January first, Paul, representing the earth, is in the position marked A, nearest to the picture of Gemini behind him, while the lamp, representing the sun, appears to him to be entering the sign of the Zodiac called Sagittarius, directly opposite across the room. Later, on April first, after three months, Paul, or the earth, has traveled a quarter of the way around the sun, has passed the pictures of Cancer and Leo on the wall behind him, and stands nearest Virgo in the position marked B. The lamp has also seemed to move through a quarter circle, has passed through the signs of Capricornus and Aquarius, and appears to Paul to be just entering the sign of Pisces, or the Fishes. In the same way the earth moves through a sign of the Zodiac every month and the sun, while really motionless, appears to also travel through a sign every month. Of course we cannot see the sign or constellation, where the sun appears to be, at the same time we see the sun, for his brightness makes the stars invisible, but if we could see the constellations by day, the sun would appear to travel from one sign of the Zodiac to the next every month.
Here is a clock of the year which shows the earth at one end of the hand, the sun in the middle, and at the other end of the hand an arrow, which points to the sign of the Zodiac where the sun appears to be, and to the date when it seems to be there to an observer on the earth. Draw the hand with the earth-end in several different positions and you will see that the sun, if viewed from the earth, would appear to be in the sign of the Zodiac exactly opposite.