Download A Revolution In Science - Empirical

A Revolution In Science - Empirical
• A dramatic change in ideas or practices.
• Any complete circle made around
something such as a planet orbiting
another body.
A Revolution In Science - Empirical
• Nicholas Copernicus
(1473 – 1543): A
Catholic cleric who was
also a mathematician,
astronomer, all around
scholar. He was
educated at Krakow
Academy (now
Jagiellonian University).
• He was born in Prussia a
part we know as Poland.
A Revolution In Science - Empirical
• He was a serious thinker
of his day.
• What he did was to start
a revolution in the
Western world with
respect to scientific
thought.
• He did not make lots of
friends in the church.
A Revolution In Science - Empirical
• Copernicus proposed
that the planets rotate
around the Sun. He did
not know why or if it
was really true.
• Copernican Principle =
Earth removed from any
position of great cosmic
significance.
Nicolai Copernici Torinensis De Revolutionibus Orbium Coelestium Libri VI
Heliocentric as opposed to geocentric
A Revolution In Science - Empirical
1. There is no one center of all the celestial circles or spheres.
2. The center of the earth is not the center of the universe, but only of gravity and of the lunar
sphere.
3. All the spheres revolve about the sun as their mid-point, and therefore the sun is the center
of the universe.
4. The ratio of the earth's distance from the sun to the height of firmament is so much smaller
than the ratio of the earth's radius to its distance from the sun that the distance from the earth
to the sun is imperceptible in comparison with the height of the firmament.
5. Whatever motion appears in the firmament arises not from any motion of the firmament, but
from the earth's motion. The earth together with its circumjacent elements performs a
complete rotation on its fixed poles in a daily motion, while the firmament and highest heaven
abide unchanged.
6. What appear to us as motions of the sun arise not from its motion but from the motion of the
earth and our sphere, with which we revolve about the sun like any other planet. The earth has,
then, more than one motion.
7. The apparent retrograde and direct motion of the planets arises not from their motion but
from the earth's. The motion of the earth alone, therefore, suffices to explain so many apparent
inequalities in the heavens.
A Revolution In Science - Empirical
• Galileo Galilei (1564
– 1642): A physicist,
mathematician,
astronomer, and
philosopher. He was
the key player in the
Scientific Revolution.
• Born in Tuscan,
Italy.
A Revolution In Science - Empirical
• Galileo Galilei provided
support for the idea of
Copernicus through his
observations.
– 1610- Sidereus Nuncius
(The Starry Messenger)
– 1632- Dialogo sopra I due
massimi sistemi del mondo
(Dialogue Concerning the
Two Chief World Systems)
A Revolution In Science - Empirical
• Other publications:
• 1590 – Pisan De Motu
(On Motion)
• 1596 - La Billancetta
(The Little Balance)
• 1606 – Le Operazioni
del Compasso
Geometrico et
Militar
A Revolution In Science - Empirical
• Tycho Brahe (1546 –
1601): He was a Danish
nobleman who was an
astronomer and
alchemist.
• He had an estate on the
island of Hven and built
a research institution
known as Uraniborg.
A Revolution In Science - Empirical
• Tycho made many important
observations and key
recordings of the locations of
celestial objects.
• He observed SN 1572 in 1572!
• What a nose!
• From 1600 till his death in
1601 he had an assistant.
A Revolution In Science - Empirical
• Johannes Kepler (15711630): He was a German
mathematician,
astronomer, and
astrologer.
A Revolution In Science - Empirical
• He produced two major
works: Astronomia nova
(1609)
A Revolution In Science - Empirical
• He produced two major
works: Harmonices
Mundi (1619).
– This is the one work that
affects all of science.
A Revolution In Science - Empirical
• Kepler took the next step in
understanding the physics of our solar
system and the motion of planets. He
deduced three empirical rules or laws.
– Empirical = the quest to first note and then
accurately describe patterns in nature.
A Revolution - Kepler’s Laws
• I. The orbital paths of the planets are elliptical
(not circular), with the Sun at one focus.
• Shape and size of planetary orbits:
Semimajor axis = the length of the long axis or the
ellipse’s size.
Eccentricity of an ellipse = the ratio of the distance
between the foci to the length of the major axis.
A Revolution - Kepler’s Laws
• II. “Law of Equal Areas” The line connecting
a planet to the Sun sweeps out equal areas in
equal times, regardless of where the planet is in
its orbit.
• An imaginary line connecting the Sun to any
planet sweeps out equal areas of the ellipse in
equal intervals of time.
– The speed of a planet changes as it goes around its
orbit.
A Revolution - Kepler’s Laws
• III. The square of the period of a planet’s
orbit, measured in years, is equal to the cube of
the semimajor axis of the planet’s orbit,
measured in AU. Harmonic Law
• The square of a planet’s orbital period is
proportional to the cube of its semi-major axis.
– (Pyears)2 = (AAU)3
– How long it takes a planet to orbit the Sun = period.
This law states the relationship between the period
of a planet’s orbit (P) and its distance from the Sun
(A).
A Revolution - Kepler’s Laws
• Kepler simply
described the orbits
of the planets, he did
not explain why they
are the way they are.
A Revolution - End of Empirical Approach
• Up to this point in the lecture we have
been discussing the Empirical Approach
or Empirical Observations.
– We have been discussing the what!
• Now we will begin to explain the why and
how of the observations.
A Revolution - Newton’s Laws
• Sir Isaac Newton
(1642-1723) - Set the
foundation for
Classical Mechanics.
Laws were published
in 1687. Known as
the Laws of Motion.
A Revolution - Newton’s Laws
• I. Newton’s First Law
– Objects at rest stay at rest, objects in motion
stay in motion.
– Every body continues in a state of rest or in
a state of uniform motion in a straight line
unless it is compelled to change that state by
a force acting on it.
A Revolution - Newton’s Laws
• The tendency of an object to keep moving in
the same direction or remain at rest is known
as inertia.
• One measure of an object’s inertia is its mass essentially the total amount of matter it
contains or what determines an object’s
resistance to a change in motion.
– The greater the mass, the greater the force needed
to change the object.
A Revolution - Newton’s Laws
• II. Newton’s Second Law
– If there is an unbalanced force acting on an
object, then the object’s motion does change.
– When a force F acts on a body of mass m, it
produces in it an acceleration a equal to
force divided by mass
• a=F/m or F = ma
A Revolution - Newton’s Laws
• III. Newton’s Third Law
– For every action or force there is an equal
and opposite reaction or force.