THE UNIVERSE IN WHICH WE LIVE 17 



has recently been subdivided into three magnitudes, as our 

 measures of brilliancy have become more exact, namely, stars 

 of i magnitude, the most brilliant, those of magnitude o, and 

 those of magnitude i. A star of magnitude i is 2.5 times as 

 bright as one of magnitude 2, (2.5) 2 or 6.25 times as bright as 

 one of magnitude 3, etc. 



But the stars that are visible to the naked eye are but a 

 fraction of those that exist. The telescope shows thousands and 

 thousands that the eye cannot see. Indeed, every time a new 

 and more powerful telescope is made and pointed to the skies 

 it shows new stars beyond the range of the old, less powerful 

 telescopes; so that just how many stars there really are no one 

 knows. Some 200,000 have already been located and mapped, 

 and it is estimated that there are at least a half-billion of them 

 in our stellar system. The Milky Way, which seems like a band 

 of hazy light crossing the sky, is made of thousands of stars so 

 numerous and so distant that their radiance blends into a mist 

 of light. Then beyond the limits of our galaxy of stars, with its 

 half-billion or more, are possibly many other galaxies, so dis- 

 tant they seem like mere flecks of hazy light, even when seen in 

 powerful telescopes. How many such exist astronomers even 

 do not guess. 



Many of these stars are almost inconceivably distant from 

 our earth. The nearest one, 61 in the constellation of Cygnus 

 (see p. 29), is so far away that, if we represent the distance from 

 the earth to the sun by i inch, the distance to this star would be 

 represented by a line yj miles long. Light traveling at the 

 enormous rate of 186,300 miles (seven and one-half times around 

 the earth) in one second, takes three and one-half years to reach 

 us from this star. Some of the stars are so far away that their 

 light only reaches the earth after traveling through space for 

 10,000 years, and that probably is not the limit. 



Stars are really suns that in all probability, judging by our 

 sun, have planets revolving about them. Is it possible they too 

 are inhabited ? If so, by what sorts of beings ? And many of 



