365¼. Because of this fact, an extra day accumulates every four years;
and to include this we add this extra day to February every “leap
year.” In this way, our celestial bookkeeping is kept fairly accurate.
Twelve months of 30 days each would give 360 days, with five days over.
It was, however, found that five days was not enough, while five and a
quarter was too much. It is interesting to note that Hipparchus, who
flourished in the 2nd century B. C., worked on this problem, and fixed
5 days and 55 m., as the time required--a truly remarkable achievement,
since it has since been found to be accurate to within less than six
minutes.
CURVED SPACE
This, and various other problems connected with the Einstein theories
may be found treated in No. 408 of the present series, “An Introduction
to Einstein,” by William F. Hudgings.
THE TEMPERATURE OF SPACE
The Earth is warmed by the sun’s rays, some of which are absorbed,
while some are reflected. But these rays themselves possess no
“heat”; they are merely minute vibrations in the ether. Heat is only
present when they strike some solid body. Consequently the vast
inter-stellar spaces are tremendously cold--probably at or about
absolute zero (-273.10°C). Our earth is not heated directly, as a man
is heated by standing in front of a blazing fire; but only by means
of electro-magnetic undulations, which traverse millions of miles of
space, colder than death, without heating them!
LIGHT IN SPACE
Space is also intensely dark; no light exists there save the faint
twinklings of distant stars. The sun illumines our earth, because its
rays are reflected from its surface; but space itself is intensely
black, just as it is intensely cold It is a “cold world” indeed, once
we have stepped off the little planet on which we dwell!
LIFE IN SPACE
All this being so, life in any form cannot very well exist in
space--since the conditions for its existence are altogether absent.
Arrhenius has, however, suggested, that the “germs of life” might
possibly be carried across millions of miles of space on dust
particles, propelled by the energy of light. This, however, is a pure
theory, which has so far received no official proof.
THE CAUSES OF AN ICE AGE
We know that our Earth has passed through several ice ages, in the
past, and various astronomical theories have been advanced in order to
explain this fact. Perhaps the most ingenious of these is that advanced
by Sir Robert Ball (see his “The Cause of An Ice Age”). Very briefly,
it is that the eccentricity of the earth’s orbit and the tilting of
the polar axis causes an ice age, or the reverse. If the northern axis
is tilted towards the sun, when nearest to it (so to say), then the
northern hemisphere will enjoy a genial climate, and if the southern
axis be thus tilted, the reverse conditions will prevail. This, and
various other theories have, however, been discussed by Finger in his
book on “The Ice Age,” in the present series, No. 327.
WHY DO STARS “TWINKLE”?
When we look at a star near the horizon, we at once notice that it
twinkles, or “scintillates,” especially in the winter time. The
phenomenon is purely atmospheric, and is due to waves of air of unequal
density sweeping across the line of sight. When viewed through a
telescope, this is sometimes magnified into actual dancing.
WHY DOES THE MOON SOMETIMES APPEAR LARGER?
It is well known that the moon often appears larger when rising or
setting--i. e., near the horizon, than when it is overhead. The same
is true of the Sun. It is hardly necessary to say that these celestial
bodies have not _actually_ increased or decreased in size! Why, then,
should we perceive them larger at some times than at others?
The reason for this is two-fold; psychological and optical. In the
first place, the Heavens do not appear to us quite round, but somewhat
flattened out, like a watch-glass. Hence the moon appears to be much
further away when it rises than it does when it is overhead, with
nothing between. The moon near the horizon is apparently larger because
it seems further away. The second reason is that the refraction of the
earth’s atmosphere gives this illusion of increased size.
ARE THE PLANETS INHABITED?
This is a much-disputed point! Various astronomers (Schiaparelli,
Lowell, etc.) have contended that they have almost indubitable evidence
that Mars is inhabited by living beings like ourselves; other
equally competent astronomers assert the contrary. Certainly, none
of the planets of our own solar system, with the possible exceptions
of Mars and Venus, could possibly be inhabited. That is universally
granted. And we have no _direct_ evidence of any other inhabited
worlds throughout space. Analogy, however, forces us to believe that,
of the millions of suns blazing in the heavens, many of them must be
attended by a planetary system such as ours; and if such be the case,
there is no reason why life should not originate and thrive thereon as
well as upon our own planet. We have, however, no means of proving or
disproving this directly.
In our own system, Venus and particularly Mars offer possibilities.
Venus probably always turns one face towards the sun, so that this
side would be tremendously hot, while the other side would be frozen
in perpetual ice. Mars is a possibility; and, as we know, great
controversy has raged regarding the habitability of this planet, and
as to its “Canals.” The interested reader may refer to Lowell’s “Mars
as the Abode of Life,” and “Mars and Its Canals” for the affirmative,
and to Maunder’s “Are the Planets Inhabited?” for the negative, side of
this question.
A FEW DEFINITIONS
What “Parallax” means. Since the earth revolves round the sun, the
stars are apparently in slightly different directions from it at
different times of the year. The difference in direction of a star as
seen from two points on the earth’s orbit which are separated by the
mean distance to the sun is the _parallax_ of the star. In other words,
the parallax of a star is the angle subtended by the major semi-axis of
the earth’s orbit, as seen from the star.
The “Orbit” of a moving body is its more or less circular passage
through space, usually around another larger body, as our earth
revolves round the sun. The “eccentricity” of the orbit consists in the
fluctuations or variations from its exact path.
The “Ecliptic” System. If we could see the stars near the sun, we
should find that the Sun apparently moves eastward among them,
completing one revolution in a year. Tracing such a path, it will be
found that it more or less coincides with the celestial equator. The
equator and the ecliptic intersect at two points; these points are the
“equinoxes” the _vernal_ equinox being the one at which the sun crosses
the equator from south to north, and the _autumnal_ equinox the other
one.
“Satellites.” These are smaller bodies which revolve round large ones,
and, so to say, attend them. All except two of the planets are known
to have satellites revolving round them, just as they revolve round
the sun. Mercury and Venus have none; the earth has the moon; Mars has
two little moons, only a few miles in diameter; Jupiter has four large
satellites and four small ones; Saturn has ten, one of which is larger
than Mercury; Uranus has four satellites, and Neptune one.
The “Planetoids.” Between Mars and Jupiter a number of small bodies
have been discovered, moving in a regular orbit; these have been
called planetoids. If some planet has once occupied this mid-way
position, and subsequently exploded, the fragments would occupy the
position occupied by the planetoids. Whether or not this is their
origin is a disputed point, which it would take us too far afield to
consider here. They suggest the possibility.
“Planets.” These are the bodies revolving round a central sun. Aside
from those constituting our own solar system, we see no planets in
space; we see suns, or stars; but if the latter have planets attendant
upon them, we cannot see them.
The point of the moon’s orbit nearest the earth is called the
_perigee_; the furthest point, the _apogee_.
TRANSCRIBER’S NOTES
Author’s spelling of “dialectric” has been retained.
Inconsistencies in hyphenation have been left unchanged.
Typos corrected:
Title page: missing opening quote in “Psychology for Beginners”
Page 13: “concenses” to “consensus”
Page 17: “equitorial” to “equatorial”, "Myriads" to "myriads"
(lowercase)
Page 49: “on my book” to “of my book”
Page 54: “litle” to “little”
Page 59: “Unanus” to “Uranus”