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0Introduction and Review
If you drop your shoe and a coin side by side, they hit the ground at the
same time. Why doesn’t the shoe get there first, since gravity is pulling
harder on it. How does the lens of your eye work, and why do your eye’s
muscles need to squash its lens into different shapes in order to focus on
objects nearby or far away. These are the kinds of questions that physics
tries to answer about the behavior of light and matter, the two things that
the universe is made of.
0.1The Scientific Method
Until very recently in history, no progress was made in answering
questions like these. Worse than that, the wrong answers written by thinkers
like the ancient Greek physicist Aristotle were accepted without question for
thousands of years. Why is it that scientific knowledge has progressed more
since the Renaissance than it had in all the preceding millennia since the
beginning of recorded history. Undoubtedly the industrial revolution is part
of the answer. Building its centerpiece, the steam engine, required improved
techniques for precise construction and measurement. (Early on, it was
considered a major advance when English machine shops learned to build
pistons and cylinders that fit together with a gap narrower than the thick-
ness of a penny.) But even before the industrial revolution, the pace of
discovery had picked up, mainly because of the introduction of the modern
scientific method. Although it evolved over time, most scientists today
would agree on something like the following list of the basic principles of
the scientific method:
(1)Science is a cycle of theory and experiment. Scientific theories are
created to explain the results of experiments that were created under certain
conditions. A successful theory will also make new predictions about new
experiments under new conditions. Eventually, though, it always seems to
happen that a new experiment comes along, showing that under certain
theory
experiment
The Mars Climate Orbiter is prepared for its mission.
The laws of physics are the same everywhere, even
on Mars, so the probe could be designed based on
the laws of physics as discovered on earth.
There is unfortunately another reason why this
spacecraft is relevant to the topics of this chapter: it
was destroyed attempting to enter Mars’ atmosphere
because engineers at Lockheed Martin forgot to
convert data on engine thrusts from pounds into the
metric unit of force (newtons) before giving the
information to NASA. Conversions are important!