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Updated Sunday 15 May, 2011 12:18 PM |
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This Day in Alternate History Blog
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Some Astronomical POD’s For Consideration Steve Condrey The recent
entry regarding different interpretations for the appearance of Halley’s Comet
prior to the battle of Hastings in 1066 led me to consider how other
astronomical situations may have impacted history (indeed, life) on Earth.
These aren’t really ASB scenarios because all could have occurred with
a slight change in conditions very early in Earth’s history or the solar
system’s history. Some are still
possible (albeit highly unlikely) today or in historical times. First of
all, we should recognize that the layout of the solar system had a huge impact
on the evolution of life on Earth. Without
a large planet like Jupiter between us and the Oort Cloud, Earth may have
experienced many more cometary impacts than it has in ATL, which would have
delayed or even eliminated the possibility of life evolving in the first place.
That’s a bit too drastic, so let’s scale things back a bit: Suppose a
Saturn-like planet is inserted into Jupiter’s orbit instead.
Saturn is only one-third the mass of Jupiter but still massive enough to
deflect many of the comets heading toward the inner solar system. Other possible effects: ---Mars
grows bigger as the asteroid belt grows smaller.
Part of the reason that Mars lost its atmosphere is because it lacks
sufficient gravity to hold any but the heaviest gases (CO2, Ar, CH4) for long
periods of time. Mars could be
somewhat bigger if it were allowed to accumulate mass from the nearby asteroid
belt, but Jupiter’s gravity prohibits this.
A smaller planet in place of Jupiter would allow Mars to gain more mass,
both from the asteroid belt and from primordial material not captured by the
other planets. The result could
lead to a larger Mars able to retain a more massive atmosphere, perhaps thick
enough to support liquid water and life. HT
addresses this scenario in ‘A World of Difference’. ---Shorter,
less frequent Ice Ages on Earth. The
main cause of Ice Ages on Earth is orbital perturbations caused by the gravity
of Jupiter and Saturn (because they are so massive) and Venus (because it is so
close). The switch to a Saturn-like
planet (let’s call it ‘Zeus’) in Jupiter’s orbit results in a 20%
reduction in the gravitational forces on Earth (based on comparison of escape
velocities for the planets in question, escape velocities having a direct
bearing on orbital mechanics). Earth
has fewer Ice Ages, which may create less evolutionary pressure on humans (or
human-analogues). Less-advanced
species like the australopithecines or the early Homo species may survive
longer, but at the expense of developing intellectual and tool-making capacity.
However, if there is an increase in cometary impacts due to the lower
mass of Zeus, intelligent life may never gain a foothold on Earth at all. Now,
here’s another notion: rather than replace Jupiter with Zeus, just switch
Jupiter and Saturn’s orbits. The
comet-shielding effect is still in place (if anything, there are *fewer* impacts
than in OTL) and there are fewer Ice Ages for Earth (but more than in the
replacement scenario). *Both* Earth
and Mars may develop intelligent life, as both planets have fewer negative
pressures against the development of life.
How advanced that life becomes is another matter entirely. Okay, now to
something a little more approachable, and possible (although not probable) even
in historical times. Asteroids
cross Earth’s orbit all the time, and some even come close to Earth itself.
One this year passed within 50,000 km of Earth, well inside the Moon’s
orbit. Impacts are likely over the
long-term and much attention has been given to the problem lately.
Much less likely, but still in the realm of possibility, is Earth
capturing an asteroid as a second moon. Asteroids
whose orbits are gravitationally ‘associated’ with Earth are known: 3753
Cruithine has a ‘horseshoe’-shaped orbit that brings it close to the
Earth-Moon system every 770 years. Another asteroid, 2002 AA29, has a very complicated orbit
that brings it close to Earth every 95 years.
An impact by another body with
either of these bodies could cause its orbit to decay enough to allow capture by
Earth’s gravity. Suppose a
larger asteroid (large enough to be plainly visible from Earth, no matter what
orbit it ends up in) was in a similar orbit and captured by Earth.
If the capture occurs in prehistoric times, human society would adapt and
develop its various cultures accordingly. The
human calendar might have ‘short months’ and ‘long months’ as well as
days and years. Religious festivals
might grow around the different cycles (as they have in our history).
Mathematics would develop more quickly as the societies that evolve start
to set up calendars and develop whatever analogue of astrology crops up. If such an
event happens in historical times, it’s very likely that astrology would be
replaced by astronomy much sooner as the old system is seen to be changeable.
I predict that a lot of astrologers end up victims of kings and emperors
who blame whatever misfortune might be on their plate at the time on the failure
of the court astrologer to predict the appearance and permanence of the new
body. New astrologers would be
appointed, and they would have to refine their predictions to account for the
new body (and develop theories as to how and why a new body—let’s call it
Selene--would appear). Given the
maturity of human society at that point in history, astrology may lose out to
astronomy much earlier than in OTL. The
Romans or Greeks certainly would try to develop a rational framework to explain
what had happened; I’m not so sure about the Egyptians or Babylonians.
What this would have done to societies very highly organized around
astronomy like the Mayans, the Aztecs, or the people who built Stonehenge is
anyone’s guess. Either they
collapse as a society because they can’t explain what happened, or they accept
it and adopt their practices to Selene as well as the original Moon. Flash
forward a few centuries to the late Middle Ages/early modern period.
Imagine what the appearance of a new and (apparently) permanent moon
would have done to the Roman Catholic Church and its adherence to Aristotle’s
view of the universe! Imagine where
Galileo may have taken his arguments if this body showed up in the early 17th
century! The Church would lose
credibility as a major intellectual force even faster than in OTL if it didn’t
revise its view of the universe. The
Protestant movement may pick up steam faster and be stronger than the one in our
history. The prospect of Selene
being cast as God’s tool to show that one side is right (or as Satan’s tool
to deceive the masses) is very likely. Either
way, this event would certainly speed up the scientific revolution as
intellectual inquiry is cast toward the problem.
The light of the new moon would shine over an earlier Enlightenment era. Another
thing to consider if Selene enters the Earth system during the early modern
period (1500-1800): navigation would be affected, as the Earth’s tides change.
Depending upon the size of Selene, Earth’s tides could be affected
hardly at all or very drastically. Considering
that tide tables are among the hardest of mathematical calculations, mathematics
would develop at a much faster pace as governments and shipping companies fund
development of new tables to accommodate the cycle of the new moon.
Calculus, developed by Newton and Leibniz independently in the 17th
century, might appear sooner (as both workers in OTL were relying upon earlier
work done by medieval and ancient mathematicians as a foundation).
The Arabs, Hindus, or Chinese may well develop basic calculus as we know
it, and later workers would develop differential equations and linear algebra as
tools to refine the multiple variables incurred by the second set of
fluctuations in the system. The
three-body problem may be replaced by a four-body (Earth-Moon-Sun-Selene)
problem in basic physics classes. Now, on to
the 20th century: the appearance of a second moon would certainly
impact the development of space exploration, as there are now two large bodies
relatively close to Earth. Let’s
assume Selene arrives in 1900—enough time for astronomers to refine its orbit
and to allow for societies to develop as in OTL up to the space age (all of the
major players in the development of space flight were born within one generation
either way of 1900). If the
Americans land on the Moon first, would the Soviets try for Selene rather than
abandon their program completely? Would
whoever landed on the closer body first find themselves trumped by a landing on
the moon that’s farther out? With
two bodies to exploit, the prospect of a treaty limiting territorial claims or
commercial exploitation of extraterrestrial bodies dims.
In fact, competition in space might increase.
Space technology would improve, but the cooperation that has grown
between the spacefaring nations in OTL probably wouldn’t evolve here. Thoughts?
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