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Chat with a friend about
an established scientific theory
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and she might reply,
"Well, that's just a theory."
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But a conversation about
an established scientific law
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rarely ends with,
"Well, that's just a law."
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Why is that?
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What is the difference
between a theory and a law,
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and is one better?
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Scientific laws and theories
have different jobs to do.
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A scientific law predicts
the results of certain initial conditions.
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It might predict your unborn
child's possible hair colors,
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or how far a baseball travels
when launched at a certain angle.
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In contrast, a theory tries to provide
the most logical explanation
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about why things happen as they do.
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A theory might invoke
dominant and recessive genes
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to explain how brown-haired parents
ended up with a red-headed child,
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or use gravity to shed light
on the parabolic trajectory of a baseball.
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In simplest terms,
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a law predicts what happens
while a theory proposes why.
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A theory will never grow up into a law,
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though the development of one
often triggers progress on the other.
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In the 17th Century, Johannes Kepler
theorized cosmic musical harmonies
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to explain the nature of planetary orbits.
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He developed three brilliant laws
of planetary motion
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while he was studying decades
of precise astronomical data
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in an effort to find support
for his theory.
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While his three laws
are still in use today,
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gravity replaced his theory of harmonics
to explain the planets' motions.
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How did Kepler get part of it wrong?
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Well, weren't handed
a universal instruction manual.
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Instead, we continually propose,
challenge, revise, or even replace
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our scientific ideas
as a work in progress.
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Laws usually resist change
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since they wouldn't have been adopted
if they didn't fit the data,
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though we occasionally revise laws
in the face of new unexpected information.
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A theory's acceptance, however,
is often gladiatorial.
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Multiple theories may compete
to supply the best explanation
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of a new scientific discovery.
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Upon further research,
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scientists tend to favor the theory
that can explain most of the data,
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though there may still
be gaps in our understanding.
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Scientists also like
when a new theory successful predicts
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previously unobserved phenomena,
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like when Dmitri Mendeleev's theory
abou the periodic table
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predicted several undiscovered elements.
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The term, "scientific theory"
covers a broad swath.
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Some theories are new ideas
with little experimental evidence
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that scientists eye with suspicion,
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or even ridicule.
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Other theories,
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like those involving the Big Bang,
Evolution, and Climate Change,
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have endured years
of experimental confirmation
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before earning acceptance by the majority
of the scientific community.
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You would need to learn more about
a specific explanation
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before you'd know how well
scientists perceive it.
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The word, "theory,"
alone doesn't tell you.
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In full disclosure,
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the scientific community has bet
on the wrong horse before:
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alchemy,
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the geocentric model,
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spontaneous generation,
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and the interstellar ether
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are just a few of many theories
discarded in favor of better ones.
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But even incorrect theories
have their value.
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Discredited alchemy was the birthplace
of modern chemistry,
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and medicine made great strides
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long before we understood the roles
of bacteria and viruses.
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That said, better theories often lead
to exciting new discoveries
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that were unimaginable
under the old way of thinking.
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Nor should we assume
all of our current scientific theories
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will stand the test of time.
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A single unexpected result is enough
to challenge the status quo.
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However, vulnerability to some potentially
better explanation
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doesn't weaken
a current scientific theory.
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Instead, it shields science from becoming
unchallenged dogma.
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A good scientific law
is a finely tuned machine,
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accomplishing its task brilliantly
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but ignorant of why it works
as well as it does.
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A good scientific theory is a bruised,
but unbowed, fighter
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who risks defeat if unable to overpower
or adapt to the next challenger.
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Though different,
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science needs both laws and theories
to understand the whole picture.
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So next time someone comments that
it's just a theory,
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challenge them to go nine rounds
with the champ
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and see if they can do any better.