ATOMIC POWER—RICHARDSON 153 
quality of the grape had changed so much that this was no longer 
possible. To this Helmholtz replied that it was more likely that the 
throats of the drinkers had changed rather than the climate of their 
country. 
Astronomers became so convinced of the truth of the contraction 
theory that they arbitrarily told geologists that the maximum age 
of the earth was 25 million years, and to adjust their evolutionary 
scale accordingly. This the geologists flatly refused to do, as they 
had reasons for believing that the age of the earth was more than 
100 million years. 
Toward the close of the century, the discovery of radioactivity by 
Becquerel and the isolation of radium by the Curies led to the uneasy 
suspicion that friction might not be the sole source of solar radia- 
tion. In 1899, T. C. Chamberlain,‘ a geologist, dared to challenge the 
contraction theory as well as boldly to predict, with startling insight, 
sources of subatomic energy. “What the internal constitution of the 
atoms be is yet open to question,” he wrote. “It is not improbable that 
they are complex organizations, and the seats of enormous energies. 
. . . Are we quite sure we have yet probed the bottom of the sources 
of energy and are able to measure even roughly its sum total?” 
With the reluctant abandonment of the contraction theory there 
followed a long interlude during which astronomers could give no 
definite answer to the question, “What is the force from which the 
sun draws its power?” They could watch radium release enough 
energy every hour to melt more than its own weight of ice, knowing 
that it could continue to do so for another 1,000 years. Application 
to the sun, however, was little more than a hopeful possibility. No 
radioactive substances had been identified in the solar atmosphere, 
and there was small prospect of detecting spectral lines of such heavy 
elements. Besides, nobody had the faintest idea whence radium 
derived its energy. Then in 1905, Einstein * published a paper of less 
than 500 words which changed the whole situation and has continued 
to exert an ever-increasing influence on modern physics. From con- 
siderations based upon the electrodynamics of moving bodies, he 
showed that if a body gives off energy, Z, in the form of radiation, its 
mass diminishes by Z/V*, where V is the velocity of light.6 From 
this he concluded, “it is not impossible that with bodies whose energy- 
content is variable to a high degree (e. g., with radium salts) the theory 
may be put to a successful test.” 
There appeared to be two ways in which mass might be converted 
into energy. The more radical involved the total annihilation of 
matter. The case generally envisaged was a head-on collision between 
* Science, vols. 9 and 10, 1899. 
5 Ann. Physik, vol. 18, p. 639, 1905. 
° This is Hinstein’s original notation. 
