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We accept today that science follows certain rules
and processes that make it a dependable source of information, but
those rules have not always been in place. Until as recently
as the 1700s, for instance, it was widely believed that living
things could arise spontaneously from non-living, dead, or waste
materials (this is called spontaneous generation),
because people saw such materials "generate" living
things like mold, or maggots. In 1688, Italian
naturalist Francisco Redi set out to test the idea with decaying
meat in two containers: one open to the air, the other
sealed. The open container meat eventually became infested
with maggots. And when critics insisted that it was simply that
sealing the second container kept spontaneous generation
from occurring, Redi did the test with an open container and one
covered with cheesecloth, through which air could circulate (he
suspected what we now know, that flies were the actual source of the
maggots, but there is no record of whether he tested that idea), and the cheesecloth-covered sample produced no
maggots. However, even after many aspects of spontaneous
generation were tested and became recognized as wrong, the basic concept persisted: when germs were first
discovered it was thought that they were a spontaneous
product of sick tissues, rather than independent-living organisms
that reproduced in the body.
It was a long road from that basic test
by Redi to
today's
scientific
method, but some of the approach he used
persists: modern science is about testing suspected
explanations of one's observations.
Observations can be
made directly through one's own personal senses, or indirectly
through instruments or second-hand from someone else's direct
observations. An explanation for one or more observations is
properly called a hypothesis. A hypothesis
should produce testable predictions or it isn't much
use scientifically, and the tests are most reliably done under controlled
conditions. The whole system is like puzzle-solving, in that
you have to notice things, decide if what you're noticing is important,
come up with explanations for those things, and test those explanations.
A good imagination is really valuable in doing science.
In biology, complete control over conditions is
hard to achieve, but scientists still strive for it. If no
alternative exists, testing may be done in the field, with
well-planned and organized series of observations that look for
evidence for the hypothesis' predictions. Controlled
experiments may be done in a laboratory environment with
different test groups, similar to how Redi did his
experiment. One group, the experimental group,
is specifically set up to test some critical aspect (called the variable,
sometimes the independent variable)
of the hypothesis; another group, the control group,
duplicates the experimental group but removes the variable (or, if
that isn't possible, changes it in some significant way). In Redi's
second test, the experimental group was the cloth-covered containers (the
cloth barrier as a test of air access but fly blockage was the variable),
with the control test being containers with no cloth over
them. Control tests may also be run to try to figure out how
outside influences (Confounding
factors,
discussed below) may be
affecting an experiment.
Results,
usually in some sort of number form (quantitative data,
as oppose to non-number qualitative data) are
collected from each group and compared. The
comparison is absolutely critical - just running an experimental
group is possible (we could give a new headache remedy to a group
of 100 people with headaches and record how much their headaches
improved), but how would you know whether your results were
directly connected to your variable - how many headaches would have
improved on their own, or improved just because the subjects were
given a pill and the expected to feel better (improvement based solely on
expectations is called the placebo effect, placebo
being an "empty" treatment)? In a proper
experiment, a control group would have been treated identically,
given pills with the remedy ingredient removed; the
difference in effects in the two groups could then be said to be an
effect of the remedy itself.
Aspects of your results that appear not from the
variable, but rather from the process of experimenting itself - the act of
treating can produce a placebo effect, for example - are called
artifacts. Parts of the experimental procedure that produce
artifacts are one type of confounding factor.
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