92 SCIENCE AND IMMORTALITY 



and experimentally by Peter Lebedew in 1901. 

 The pressure is small : the light pressure on the 

 whole earth is only 70,000 tons, but even a slight 

 pressure would be sufficient to repel these small 

 electrons. We have, thus, gravity and positive 

 electricity attracting the electrons, and light 

 pressure repelling them. In the case of such 

 small bodies, which are almost all surface, it is 

 certain that the light pressure would be stronger 

 than gravitation, and the only question is — Would 

 it be strong enough to overcome the attractive 

 force of the positive electricity ? To this final 

 question there can be but one answer : that un- 

 doubtedly at times, when the sun blazes up and 

 the sun-spots enlarge, the light pressure is sufficient 

 to destroy the equilibrium between the negative 

 and positive electricity, and to hurl the electrons 

 across the ninety-three million miles between the 

 sun and the earth. Long before the relationship 

 was understood it was noted that there was " an 

 almost perfect parallelism " between the intensity 

 of auroral phenomena and the abundance of sun- 

 spots, and that any flare-up of the sun was followed 

 by splendid auroras. When the electrons reach 

 the magnetic field of the earth (the earth is, of 

 course, a magnet), they are conducted by the mag- 

 netic lines of force, in a series of spirals, toward the 

 poles, and on their way through the outer atmos- 



