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PHYSICS OF THE IMPOSSIBLE
tional field squeezes the moon like a rubber ball, creating friction deep
within its core, which in turn could cause the ice cover to melt. Since
there are over one hundred moons in our solar system alone, this
means that there could be an abundance of life-supporting moons in
our solar system outside the Goldilocks zone. (And the 250 or so giant
extrasolar planets so far discovered in space might also have frozen
moons that can support life.)
Furthermore, scientists believe the universe could be peppered
with wandering planets that no longer circle around any star. Because
of tidal forces, any moon orbiting a wandering planet might have liquid oceans under its ice cover and hence life, but such moons would
be impossible to see by our instruments, which depend on detecting
light from the mother star.
Given that the number of moons probably greatly outnumbers the
number of planets in a solar system, and given that there could be millions of wandering planets in the galaxy, the number of astronomical
bodies with life-forms in the universe might be much larger than previously believed.
On the other hand, other astronomers have concluded, for a variety
of reasons, that the chances for life on planets within the Goldilocks
zone are probably much lower than originally estimated by Drake.
First, computer programs show that the presence of a Jupiter-sized
planet in a solar system is necessary to fling passing comets and meteors into space, thereby continually cleaning out a solar system and
making life possible. If Jupiter did not exist in our solar system, Earth
would be pelted with meteors and comets, making life impossible. Dr.
George Wetherill, an astronomer at the Carnegie Institution in Washington, D.C., estimates that without the presence of Jupiter or Saturn
in our solar system, the Earth would have suffered a thousand times
more asteroid collisions, with a huge life-threatening impact (like the
one that destroyed the dinosaurs 65 million years ago) occurring every
ten thousand years. "It's hard to imagine how life could survive that
extreme onslaught," he says.
Second, our planet is blessed with a large moon, which helps to
stabilize the Earth's spin. Extending Newton's laws of gravity over mil-
PHYSICS OF THE IMPOSSIBLE
tional field squeezes the moon like a rubber ball, creating friction deep
within its core, which in turn could cause the ice cover to melt. Since
there are over one hundred moons in our solar system alone, this
means that there could be an abundance of life-supporting moons in
our solar system outside the Goldilocks zone. (And the 250 or so giant
extrasolar planets so far discovered in space might also have frozen
moons that can support life.)
Furthermore, scientists believe the universe could be peppered
with wandering planets that no longer circle around any star. Because
of tidal forces, any moon orbiting a wandering planet might have liquid oceans under its ice cover and hence life, but such moons would
be impossible to see by our instruments, which depend on detecting
light from the mother star.
Given that the number of moons probably greatly outnumbers the
number of planets in a solar system, and given that there could be millions of wandering planets in the galaxy, the number of astronomical
bodies with life-forms in the universe might be much larger than previously believed.
On the other hand, other astronomers have concluded, for a variety
of reasons, that the chances for life on planets within the Goldilocks
zone are probably much lower than originally estimated by Drake.
First, computer programs show that the presence of a Jupiter-sized
planet in a solar system is necessary to fling passing comets and meteors into space, thereby continually cleaning out a solar system and
making life possible. If Jupiter did not exist in our solar system, Earth
would be pelted with meteors and comets, making life impossible. Dr.
George Wetherill, an astronomer at the Carnegie Institution in Washington, D.C., estimates that without the presence of Jupiter or Saturn
in our solar system, the Earth would have suffered a thousand times
more asteroid collisions, with a huge life-threatening impact (like the
one that destroyed the dinosaurs 65 million years ago) occurring every
ten thousand years. "It's hard to imagine how life could survive that
extreme onslaught," he says.
Second, our planet is blessed with a large moon, which helps to
stabilize the Earth's spin. Extending Newton's laws of gravity over mil-