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The temperature around
us, if there be anything that can be called temperature, is produced
solely by stellar radiation. I need not say how low that is in the
scale, or that it would be the temperature to which our Earth should
fall, if the Sun were suddenly extinguished."
"Little fear of that for a few more million years," said M'Nicholl.
"Who can tell?" asked Ardan. "Besides, even admitting that the Sun will
not soon be extinguished, what is to prevent the Earth from shooting
away from him?"
"Let friend Michael speak," said Barbican, with a smile, to the Captain;
"we may learn something."
"Certainly you may," continued the Frenchman, "if you have room for
anything new. Were we not struck by a comet's tail in 1861?"
"So it was said, anyhow," observed the Captain. "I well remember what
nonsense there was in the papers about the 'phosphorescent auroral
glare.'"
"Well," continued the Frenchman, "suppose the comet of 1861 influenced
the Earth by an attraction superior to the Sun's. What would be the
consequence? Would not the Earth follow the attracting body, become its
satellite, and thus at last be dragged off to such a distance that the
Sun's rays could no longer excite heat on her surface?"
"Well, that might possibly occur," said Barbican slowly, "but even then
I question if the consequences would be so terrible as you seem to
apprehend."
"Why not?"
"Because the cold and the heat might still manage to be nearly equalized
on our globe. It has been calculated that, had the Earth been carried
off by the comet of '61, when arrived at her greatest distance, she
would have experienced a temperature hardly sixteen times greater than
the heat we receive from the Moon, which, as everybody knows, produces
no appreciable effect, even when concentrated to a focus by the most
powerful lenses."
"Well then," exclaimed Ardan, "at such a temperature--"
"Wait a moment," replied Barbican. "Have you never heard of the
principle of compensation? Listen to another calculation. Had the Earth
been dragged along with the comet, it has been calculated that at her
perihelion, or nearest point to the Sun, she would have to endure a heat
28,000 times greater than our mean summer temperature. But this heat,
fully capable of turning the rocks into glass and the oceans into vapor,
before proceeding to such extremity, must have first formed a thick
interposing ring of clouds, and thus considerably modified the excessive
temperature. Therefore, between the extreme cold of the aphelion and the
excessive heat of the perihelion, by the great law of compensation, it
is probable that the mean temperature would be tolerably endurable."
"At how many degrees is the temperature of the interplanetary space
estimated?" asked M'Nicholl.
"Some time ago," replied Barbican, "this temperature was considered to
be very low indeed--millions and millions of degrees below zero. But
Fourrier of Auxerre, a distinguished member of the _Acadιmie des
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