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20th-century philosopher of science
Karl Popper pointed out, it can only
disprove things. Every experiment
that gives predicted answers is
supporting evidence, but one
experiment that fails may bring
an entire theory crashing down.
Over the centuries, long-held
concepts such as a geocentric
universe, the four bodily humors,
the fire-element phlogiston, and a
mysterious medium called ether
have all been disproved and
replaced with new theories. These
in turn are only theories, and may
yet be disproved, although in many
cases this is unlikely given the
evidence in their support.
Progression of ideas
Science rarely proceeds in simple,
logical steps. Discoveries may be
made simultaneously by scientists
working independently, but almost
every advance depends in some
measure on previous work and
theories. One reason for building
the vast apparatus known as the
Large Hadron Collider, or LHC, was
to search for the Higgs particle,
whose existence was predicted
40 years earlier, in 1964. That
prediction rested on decades of
theoretical work on the structure of
the atom, going back to Rutherford
and the work of Danish physicist
Niels Bohr in the 1920s, which
depended on the discovery of the
electron in 1897, which in turn
depended on the discovery of
cathode rays in 1869. Those could
not have been found without the
vacuum pump and, in 1799, the
invention of the battery—and so the
chain goes back through decades
and centuries. The great English
physicist Isaac Newton famously
said, “If I have seen further, it is
by standing on the shoulders of
giants.” He meant primarily Galileo,
but he had probably also seen a
copy of Alhazen’s Optics.The first scientists
The first philosophers with a
scientific outlook were active in
the ancient Greek world during the
6th and 5th centuries BCE. Thales
of Miletus predicted an eclipse of
the Sun in 585 BCE; Pythagoras set
up a mathematical school in what
is now southern Italy 50 years later,
and Xenophanes, after finding
seashells on a mountain, reasoned
that the whole Earth must at one
time have been covered by sea.
In Sicily in the 4th century BCE,
Empedocles asserted that earth,
air, fire, and water are the “fourfold
roots of everything.” He also took
his followers up to the volcanic
crater of Mt. Etna and jumped in,apparently to show he was
immortal—and as a result we
remember him to this day.Stargazers
Meanwhile, in India, China, and
the Mediterranean, people tried to
make sense of the movements of
the heavenly bodies. They made
star maps—partly as navigational
aids—and named stars and groups
of stars. They also noted that a
few traced irregular paths when
viewed against the “fixed stars.”
The Greeks called these wandering
stars “planets.” The Chinese
spotted Halley’s comet in 240 BCE
and, in 1054, a supernova that is
now known as the Crab Nebula. ❯❯INTRODUCTION
If you would be a real seeker
after truth, it is necessary
that at least once in your
life you doubt, as far as
possible, all things.
René Descartes