Geoscience Reference
In-Depth Information
support them (might be wrong) and dangerous to oppose them (might be right). The best
course is to ignore them until forced to face them. Even then, respect for the brevity of life
and professional caution lead most scientists to wait until someone they trust, admire, or
fear supports or opposes the theory. Then they get two for one—they can come out for or
against without having to actually read it, and can do so in a crowd either way. This, in a
nutshell, is how the plate-tectonics “revolution” took place.”
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Paul was clearly convinced this was true of the Snowball. He was certainly doing his best to force
other geologists to face up to the theory. But it wasn't just Paul's
style
that made his colleagues object
to the Snowball theory. There was another reason why many people found the theory discomfiting and
even dangerous: it was a theory that required its proponents to think what to geologists was unthink-
able. The Snowball Earth was different in almost every characteristic from the planet we see today.
Accept Paul and Dan's theory, and you have to imagine our home planet behaving like Mars or Europa
or some other alien place. That was more than enough to make many geologists shiver.
The problem was that the Snowball—as Paul described it—violated a key geological maxim called
“uniformitarianism”. This rule was first articulated in the eighteenth century, when geology in its mod-
ern scientific sense was born, and all geologists learn it at their mother's knee. It says that the present
is the key to the past. The general assumption behind this rule is that the same things happening in the
world today have been happening throughout Earth's history. Uniformitarianism is generally a good
world worked, and you risk straying into the world of mysticism and magic rather than accessible,
empirical science.
But there are some phenomena that don't show up in the everyday world, and yet are no less sci-
entifically valid for all that. Uniformitarianism encountered one of its most serious challenges in the
1980s, when Walter and Luis Alvarez succeeded in convincing most—if not quite all—of the scientif-
ic world that the dinosaurs were killed when Earth was struck by a giant asteroid.
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Their theory was,
at first, most unpopular. Invoking some outside celestial agency for the dinosaur extinctions contra-
vened the law of uniformity; it was like attributing it to an act of God rather than to some ordinary and
perfectly explicable Earthly process. But then researchers found a huge crater from exactly the right
time, off the coast of modern Mexico. Just because you can't see mighty asteroids hitting the Earth
and destroying untold species of animals and plants today, the message ran, that doesn't mean it never
happened.
And there are plenty of other reasons not to trust a simple reading of the world around you. You
could do very sensible and careful experiments in the everyday world and end up thinking that time
flows smoothly, that rulers are the same length for everyone, and that clocks tick at the same rate re-
gardless of where you are or how fast you're moving. All of these assumptions are wrong. On large
enough or small enough scales, the world doesn't work like that at all. Clocks can tick more slowly
or quickly, time comes in packets, objects can be in two places at once, and the faster something is
travelling, the shorter it gets.
All of these things were discovered in the early part of the last century, when relativity theory and
quantum physics shattered our comfortable connections between direct experience and natural laws.
There's a reason our intuition is often wrong: we evolved that way. In our normal lives we don't deal
with relativistic or quantum scales. Nor do we deal with vast geological timescales.
And that fact has not escaped Paul and Dan. They both have a habit of talking about the Snowball
as an “outrageous hypothesis”. This is a nice touch, with an instant resonance for all geologists. The
