MAN’S THEATER OF ACTION 
of millions of years. Back farther still the most ancient 
traces of life itself fade out. 
Was this the dawn of time for our earth? We believe 
not. Nature furnishes a calendar in the minerals which 
bear the radioactive elements, radium, thorium, uranium, 
and their degenerated products, lead and helium. Radium, 
for example, constantly decomposes, yielding helium and a 
temporary element called radium emanation. The emana- 
tion itself decomposes into more helium and a second 
temporary element. After five similar transformations the 
end product, besides the gas helium, is the familiar metal 
lead. 
Such are the works of nature’s time clock. The time 
element consists in this, that radium loses half of its weight 
in 1,700 years, producing helium and lead at rates which 
are now well known, and which no known agency can 
either hasten or retard. Basing their estimates on the 
quantities of helium and of lead in certain of the very old- 
est rocks which contain such chemical elements as uranium 
and radium, and on other similar data, students have now 
come to a general agreement that the primeval earth’s 
crust can not be less than a billion years of age. 
Was this, then, the beginning of time? Evidently not, 
for the chemicals in the stars are all so hot as to be gaseous, 
whereas the crust of the earth is so cool as to be solid. 
Immense periods of time must have elapsed before the 
material which combined to form the solid earth was de- 
veloped from the gases of which once it formed a part. 
This brings us to the newest view relating to the length of 
time, which grows out of the consideration of solar and 
stellar energy. Our sun and the other stars constitute im- 
mense bodies hundreds of thousands of times more massive 
than the earth. Owing to their tremendous temperatures 
they constantly give off visible and invisible rays having 
enormous energy. Even at the earth’s immense distance 
the sun rays contain over a horsepower of energy per square 
yard. Equally intense are the sun rays in all directions, so 
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