Early in the 20th century, Robert H. Goddard patented the basic rocket
design that remains in use to this day. In a 1919 report, Goddard
described the principles of rocket travel in outer space, and in 1920 the
Smithsonian Institution, which had financed some of Goddard's work,
summarized the gist of this article in a press release. Journalists were
skeptical. An editorial in The New York Times reminded the public that
it would be impossible for a rocket to function in a vacuum, and
dismissed Goddard with, "Of course, he only seems to lack the knowl-
edge ladled out daily in high schools." To its credit the Times eventually
printed a retraction, but not until 1969 as U.S. astronauts prepared for
the first moon landing ( Wohleber, 1996).

Before he wrote this article, Goddard first proved that rocket
engines could operate in a vacuum by testing an actual engine in a
vacuum chamber. This early model not only worked in a vacuum,
but it worked 20% better in the vacuum than in air. Goddard was
well aware of the traditional belief that engines cannot work in a
vacuum, but he settled the question with experimental evidence rather
than plausible arguments. The chief objective of this book is to offer
tools for distinguishing between belief and evidence.

Goddard did much more than assert that his rocket engine could
work in a vacuum. He described his experiments in detail: how he
created a vacuum in his experimental chamber, how he measured the
vacuum, how he measured the output of his engine, and so on. He
described his experimental operations in such detail that other scien-
tists could evaluate his evidence and repeat his experiments. They
could reach their own conclusions. Operational definitions tie theories
and explanations to observation and experiment.

Can blind human beings locate objects at a distance? For hundreds,
perhaps thousands, of years natural philosophers debated this ques-
tion. Many cultures believe that losses such as blindness stimuluate
compensation. To skeptics, compensation seems like a sentimental
denial of the harshness of nature and the principle of survival through
fitness. Believers retold dramatic stories about the remarkable abilities
of blind people. Skeptics found it easy to discount such informal,

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