It is very interesting to observe the sky at night, to see the constellations, the stars and the planets. To the casual eye everything may appears to be the same. There are the well-known constellations, rising one by one, looking exactly the same as they did last year. But it is not so.
Everchanging sky: above — 100,000 years ago; in the middle — today and below — in100, 000 years time
The sky represents an everchanging picture as it goes round the Polar Star at night. This nightly motion is, of course, the result of the earth's rotation about its axis. As is known it takes it 24 hours to complete a rotation. The picture of the sky changes not only from hour to hour, but from month to month. In England the Lion constellation can be seen rising at 9 p.m. in January and in February at 7 p. m.
The monthly motion is the result of the Earth's yearly revolution around the Sun.
If we study the changes that take place from year to year, we shall see that in February 1961 the planet Jupiter was in the constellation of the Archer whereas in February 1965 we could see it near the Bull.
The planet Mars in 1961 was in the constellation of the Twins. In February 1965 it was at the back of the Lion.
Nothing is quite the same or ever will be. Even the stars move about.
The diagram attached is of the well-known constellation, the Dipper. It shows the changes that have taken place in it during the past 100,000 years and also what it will look like in 100,000 years time.
constellation -- созвездие
the result of the earth's rotation about its axis – результат вращения земли вокруг своей оси
to complete a rotation – завершить оборот
the Lion – созвездие Льва
the Archer – созвездие Стрельца
the Bull – созвездие Тельца
in the constellation of the Twins – в созвездии Близнецов
the Dipper – Медведица (Ковш)
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