of worlds revolving round the numerous
and distant stars that people Infinitude; suns more or less analogous to
that by which we are illuminated, and generally speaking of larger bulk,
although our Sun is a million times larger than our planet.

Among the ancients, before the isolation of our globe in Space and the
motions that incessantly alter its position were recognized, the Earth
was supposed to be the immobile lower half of the Universe. The sky was
regarded as the upper half. The ancients supplied our world with
fantastic supports that penetrated to the Infernal Regions. They could
not admit the notion of the Earth's isolation, because they had a false
idea of its weight. To-day, however, we know positively that the Earth
is based on nothing. The innumerable journeys accomplished round it in
all directions give definite proof of this. It is attached to nothing.
As we said before, there is neither "above" nor "below" in the Universe.
What we call "below" is the center of the Earth. For the rest the Earth
turns upon its own axis in twenty-four hours. Night is only a partial
phenomenon, due to the rotary motion of the planet, a motion that could
not exist under conditions other than that of the absolute isolation of
our globe in space.

[Illustration: FIG. 2.--The earth in space. June solstice, midday.]

Since the Sun can only illuminate one side of our globe at one moment,
that is to say one hemisphere, it follows that Night is nothing but the
state of the part that is not illuminated. As the Earth revolves upon
itself, all the parts successively exposed to the Sun are in the day,
while the parts situated opposite to the Sun, in the cone of shadow
produced by the Earth itself, are in night. But whether it be noon or
midnight, the stars always occupy the same position in the Heavens,
even when, dazzled by the ardent light of the orb of day, we can no
longer see them; and when we are plunged into the darkness of the night,
the god Phoebus still continues to pour his beneficent rays upon the
countries turned toward him.

The sequence of day and night is a phenomenon belonging, properly
speaking, to the Earth, in which the rest of the Universe does not
participate. The same occurs for every world that is illuminated by a
sun, and endowed with a rotary movement. In absolute space, there is no
succession of nights and days.

Upheld in space by forces that will be explained at a later point, our
planet glides in the