Early Ideas aboutthe Universe

1 Early man got hisideas about the universe by looking at the stars as you do.He

observedcarefully,and learned many things about the sun,the moon,and the stars.

2 Suppose you wereasked to collect evidence about the sun as early man did.You might

go out morning aftermorning and see it come up in the east.Even on cloudy mornings,you

would observe thatthe darkness goes away and the world becomes light.You might not see

the sun but would besure it is there,because you notice that the earth warms up.As you

continued,the sunclimbs higher in the sky each day during part of the year. It stays in the

sky longer. The earthgets warmer. Things begin to grow. It is spring and then summer.

3 After a while thesun stays in the sky for shorter and shorter periods.Many plants begin

to die.Leavesfall.Winter comes.Year after year this is repeated and you cannot tell

exactly why ithappens.But you realize that the sun seems to make the difference.

Primitive（原始的）man felt that since the sun was sopowerful it must be a god. It may

seem silly to us nowto worship（崇拜）a sun-god,but primitive man was right about the

importance of thesun to life on earth.

4 You have been toldthat the world is round.But suppose no one had ever taught you

that the world waslike a huge ball.Would you have ever thought of it yourself?You cannot

see the curve（曲线）of the earth at once. You wouldhave no idea of how big it was.

That's why early manbelieved that the earth was small and flat.Such ideas appeared from

the evidence theyhad.

5 If you watch thestars night after night,you will see them rise and set.As you look at

the sky,it is notdifficult to imagine that you are in the center of a vast collection oftwinkling

（闪烁）lights. Someearly astronomers（天文学家）believed the sky was a crystalshell or

series of crystalshells,one inside the other. They believed this because that is what the

night sky lookedlike.For many centuries,men believed that the earth was the center of

the universe andthat the sun,the moon,and the stars circled around it.Early man thoughtthe earth was small and flat because_________.

A.he did not observethe sun carefully enough

B.he could not seeits curve

C.the sun,the moonand the stars seemed to move around it

D.the earth circlesaround the sun

E.it looked likethat at night