PROBLEMS OF MODERN SCIENCE 



in length, and the wall is constructed of similar 

 blocks. In the foreground is the sun, the various 

 stars are represented by balls placed upon rods 

 which serve to define their positions. Two of 

 the stars are suspended by strings below the pave- 

 ment. The nearest star is Sirius, whose distance 

 is over 8 light-years. The distant group is that 



Fig. 7. TAURUS CLUSTER 



The small arrows indicate the direction in which the stars to 

 which they are attached are moving. 



formed by the stars in the Plough. All these 

 stars are moving away from the sun along this 

 corridor of time at the rate of 1 1^ miles per second, 

 and 160,000 years will elapse before they have 

 moved forward a distance equal to the side of one 

 of the blocks. 



The diagram makes it clear that as an effect 

 of perspective, stars which are really moving on 

 parallel lines will appear to converge to a point. 

 This convergence of paths is very marked in the 

 case of a cluster of stars in Taurus, whose motions 

 were investigated by Boss (Fig. 7). 

 62 



