The Science Book

(Elle) #1

43


See also: Nicolaus Copernicus 34–39 ■ Isaac Newton 62–69


SCIENTIFIC REVOLUTION


collected. By letting the ball go at
different points on the ramp, he
showed that the distance traveled
depended on the square of the time
taken—in other words, the ball
accelerated down the ramp.


The law of falling bodies
Galileo’s conclusion was that bodies
all fall at the same speed in a
vacuum, an idea later developed
further by Isaac Newton. There is a
greater force from gravity on a larger
mass, but the larger mass also


needs a bigger force to make it
accelerate. The two effects cancel
each other out, so in the absence of
any other forces, all falling objects
will accelerate at the same rate. We
see things falling at different rates
in everyday life because of the
effect of air resistance, which slows
objects down at different rates
depending on their size and shape.
A beach ball and a bowling ball
of the same size will initially
accelerate at the same rate. Once
they are moving, the same amount
of air resistance will act on them,
but the size of this force will be a
much greater proportion of the
downward force on the beach ball
than the bowling ball, and so the
beach ball will slow down more.
Galileo’s insistence on testing
theories with careful observation
and measurable experiments marks
him, like Alhazen, as one of the
founders of modern science. His
ideas on forces and motion paved
the way for Newton’s laws of motion
50 years later and underpin our
understanding of movement in the
universe, from atoms to galaxies. ■

Objects of different
masses appear to fall at
different rates.

Without air resistance,
all objects would fall at
the same rate.

All moving objects are
affected by air resistance.

A falling body
accelerates
uniformly.

Count what is countable,
measure what is measurable,
and what is not measurable,
make it measurable.
Galileo Galilei

Galileo Galilei Galileo was born in Pisa, but
later moved with his family to
Florence. In 1581, he enrolled
in the University of Pisa to
study medicine, then switched
to mathematics and natural
philosophy. He investigated many
areas of science, and is perhaps
most famous for his discovery of
the four largest moons of Jupiter
(still called the Galilean moons).
Galileo’s observations led him to
support the Sun-centered model
of the solar system, which at
the time was in opposition to the
teachings of the Roman Catholic
Church. In 1633, he was tried and

made to recant this and other
ideas. He was sentenced to
house arrest, which lasted
the rest of his life. During
his confinement, he wrote a
book summarizing his work
on kinematics (the science
of movement).

Key works

1623 The Assayer 
1632 Dialogue Concerning the
Two Chief World Systems 
1638 Discourses and
Mathematical Demonstrations
Relating to Two New Sciences 
Free download pdf