THE sun's journey THROUGH SPACE 



Two Other extremely delicate methods of finding the 

 sun's distance are reserved for the mathematician, both of 

 which are based upon the subtle attraction of gravitation. 

 The first is called the lunar method of finding the sun's 

 parallax, which depends upon the ratio between the 

 diameter of the moon's orbit and the distance of the sun. 

 It was this method that led Hansen in 1854 to throw doubt 

 upon the generally accepted value of the sun's distance 

 of those days. The other method, founded upon the 

 same influence exerted by gravitation, enables the 

 astronomer, by observing the perturbations of the planets, 

 to compute the ratio between the masses and distance of 

 the whole solar family. 



There still remains one other method of solving the 

 problem we are dealing with, and it is known as the 

 physical method, by which the velocity of light is made to 

 disclose the distance separating the earth from the sun. 

 Light travels at a speed of 186,327 miles a second, and we 

 have only to multiply these figures by the number of 

 seconds required by light to reach us from the sun to get 

 at its distance. After combining all the results of this 

 last method, which Prof. Young says outranks all others, 

 as it gives directly the distance of the sun and the parallax 

 only indirectly, he obtains 8.80" as the solar parallax, giv- 

 ing a final distance of 92,892,000 miles. We may there- 

 fore rest assured that for all practical purposes 93,000,000 

 miles is the limit we can obtain at present, and that, at 

 last, we hold securely in our hands the key which unlocks 

 the mysteries of the stars around us. 



