Copernicanism is interesting to me in how it came about and
what was used to argue its validity. It required a physical theory that
Copernicus was unaware of, but his system demanded its existence. It is from
this requirement that it is possible to move from the realm of impetus
mechanics to inertial mechanics.
This to me shows the morphing and growing of an idea and
understanding of the world as more is learned and understood. More questions
get asked and answered which refines what came before it. Luckily, it also
leads us to yet more questions that we deem worth asking.
Wolff pieces together how Copernicus, Benedetti, and Galileo
used impetus mechanics to explain what they saw and how this becomes inertial
mechanics because it has no other choice if it is to work. The Earth itself has
to be able to rotate about its own axis for the Copernican system to work, and
the argument was put forth that it does so because it is spherical. That is
what spheres are able to do. The universe is made out of spheres, so the Earth
is able to rotate.
Building from that is the concept of forced and natural
motions. Forced motions are motions that require an external force to act upon
a body. Natural motions are simple motions and suit the "nature" of
simple bodies. Spheres are considered to be simple bodies, and their simplicity
is realized by their form and their motion.
I will be honest in saying that wrapping my head around the
mental gymnastics that are being used to justify all of this is giving me a
slight headache as it all seems a bit much, but then again, our understanding
has advanced from what Copernicus had to work with when he made his statements.
For students, it is very important to show how theories and
ideas evolve over time. They can be morphed or outright discarded. Parts of a
discarded theory can come find new meaning after a new discovery. It could be
said that the world of science is ever evolving, but perhaps it would be better
to say that we're just becoming better at describing what it is that we have seen
all along.
Michael Wolff, "Impetus mechanics as a physical argument for Copernicanism: Copernicus, Benedetti, Galileo," Science in Context, Vol. 1, pages 215-256 (1987)
