4 i2 GENERAL SCIENCE 



telescope, they appear like huge balls illuminated. Some 

 of their moons can also be seen. 



It takes about eight minutes for the light to come 

 from the sun to the earth, a distance of about ninety-two 

 million miles. This means that light travels at the 

 enormous speed of 186,000 miles per second, or seven 

 and one-half times around the earth if it could go in a 

 curved line. 



The stars other than the planets are called fixed stars, 

 and the nearest of these, Alpha Centauri, is so far away 

 that 4.4 years are required for the light to come from it 

 to the earth. It takes about 45 years for the light to 

 come from the North Star. Some of the stars are so far 

 away that several hundred years are required for the light 

 to reach the earth. 



287. Meteors. Meteors are also known as "shooting 

 stars." Some are composed mostly of iron and others of 

 stone. They vary in size from small shot to hundreds of 

 pounds. One found in Texas weighs 1635 pounds; it is 

 now in the Peabody Museum of Yale University. The 

 same museum has hundreds of smaller ones also. Other 

 museums in the United States and Europe contain thou- 

 sands of meteorites. 



Meteors are flying through space at a speed of about 

 35 miles per second, and when they strike the earth's 

 atmosphere they are made white hot by the impact and 

 by the friction produced while passing into the air. They 

 strike the earth's atmosphere by the million every day, 

 but nearly all are vaporized before they penetrate very far 

 and never become visible. Those which are large enough 

 to be seen rarely become visible until they are within 

 70 miles, and usually disappear before they come within 

 30 miles of the earth. Only a few have been seen to fall 



