The Moon’s tides have been an ever-present force in Earth’s
history, shaping the landscape and the lives of the creatures that
inhabit it. Now there’s a tantalising hint that the galactic tide may
have played a significant role in Earth’s past.
The work comes from Jozef Klacka at Comenius University in the
Slovak Republic. He has calculated the strength of the galactic tide
and its effect on the Solar System. His conclusion is that the tide
is strong enough to significantly effect the orbital evolution of
Oort Cloud comets.
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That’s a fascinating result. We’ve long known that the Moon’s
tides must have been crucial for the evolution of life on Earth. The
constant ebb and flow of the oceans would have left sea life stranded
on beaches, forcing adaptations that allowed these creatures to cope
with conditions on land.
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Astrobiologists also believe that comets played an important part
in the development of life on Earth because the atmosphere and oceans
were seeded, at least in part, by comets. By that way of thinking,
the forces and processes that have shaped evolution stretch to the
edge of the Solar System.
But if the galactic tide plays a role in sending these comets our
way, then it looks as if we’re part of a much larger web. Could it be
that Earth and the life that has evolved here, is crucially
dependent, not just on our planet, our star and our local
interplanetary environment, but on the Milky Way galaxy itself?
Klacka has a lot more work to do to prove that the galactic tide
plays such a role. But it might just be that the field of
astrobiology has become a whole lot bigger.
