THE WAY OF SCIENCE - PowerPoint PPT Presentation

1 / 36
About This Presentation
Title:

THE WAY OF SCIENCE

Description:

The center of the epicycle moves with unchanging speed, as seen from the equant ... that motions were both circular and uniform (epicycle theory too complex) ... – PowerPoint PPT presentation

Number of Views:49
Avg rating:3.0/5.0
Slides: 37
Provided by: saou6
Category:
Tags: science | the | way | epicycle

less

Transcript and Presenter's Notes

Title: THE WAY OF SCIENCE


1
CHAPTER 1
  • THE WAY OF SCIENCE

2
SUMMARY
  • Stardust An Invitation to Science
  • Observing the Night Sky
  • Ancient Greek Theories An Earth-Centered
    Universe
  • Copernicuss Theory A Sun-Centered Universe
  • Keplers Theory A Sun-Focused Universe

3
  • 1.1 AN INVITATION TO SCIENCE
  • Science Observing and understanding the natural
    world
  • Reasons for learning science
  • expanded awareness of the universe
  • problems of modern society and their solutions
  • understanding everyday technology
  • Physics The study of universal phenomena

4
  • What is Physics?

"Physics" could best be described as the study of
(a) matter. (b) atoms in motion. (c) the
absolute, or certain, truths about the natural
world. (d) the general principles underlying
natural phenomena. (e) the application of
science to the needs of human beings.
5
  • 1.2 OBSERVING THE NIGHT SKY
  • How does science operate
  • Observe phenomena in nature
  • Hypothesize on why they behave the way they do
  • Test the hypothesis to se if it works
  • If the hypothesis works, it is promoted to theory
  • A theory should predict phenomena that have not
    been observed yet
  • Astronomy Study of stars and other objects in
    space
  • In this chapter, we will look at how various
    theories on astronomy evolved with time.

6
  • 1.3 ANCIENT GREEK THEORIES
  • Babylonians and Egyptians (3000 BC) Knew about
    starts, sun, moon, and 5 planets
  • Greeks (500BC) Sought to understand their motion
  • Each sphere rotates at a uniform rate around
    Earth, roughly once a day.
  • Pythagoras Pythagoreans formed a cult that
    believed in the importance of abstract ideas ?
    Mathematics

7
  • They were persecuted
  • Deep influence on Plato and Aristotle
  • Aristotle (200 years later) Earth is spherical
  • Ships sink little by little below the horizon
  • In Northern lands, noontime sun is lower in the
    sky
  • Shadow cast by Earth on the moon, observed during
    eclipse, is spherical

8
  • Careful observations show that Mars generally
    moves from East to West at a variable rate and
    occasionally changes direction ? Retrograde motion
  • Aristarchus theory Sun at Center of Universe ?
    dismissed because
  • Earth is not the center of Heavens?
  • Absurd that Earth moves.Too big Birds and
    clouds should be left behind

9
  • Epicycle theory Mars has a deferent and an
    epicycle (Fig. 10)
  • Ptolemy Figs. 11 and 13
  • He introduced 2 new ideas
  • Earth is displaced slightly from the center of
    the deferent
  • The center of the epicycle moves with unchanging
    speed, as seen from the equant

10
  • Ptolemy checked his theory with many quantitative
    measurements
  • Used long sighting rods with a scale to measure
    the angular position of a planet
  • Measured angle between the horizontal and the
    direction of the planet.
  • Ptolemys theory gave a good explanation that
    agreed with the measured quantities
  • These devices were accurate to within 0.2 degrees
  • However, telescopes were not invented yet!!!

11
  • 1.4 COPERNICUS THEORY
  • Polish (1473-1543 AD)
  • He revealed his theory on his deathbed
  • He looked at Earth as an object similar to
    other objects in space
  • Like Pythagoras, he believed that motions were
    both circular and uniform (epicycle theory too
    complex)
  • A sun-centered universe

12
  • The figure below shows the position of Earth and
    Mars at 9 different times. Mars is in retrograde
    motion during
  • Times 4 to 6
  • Times 3 to 5
  • Times 1 to 5
  • Times 4 to 7
  • None of the time

Figure 1.16
13
  • Questions that Copernicus could not answered at
    that time
  • How can Earth move?
  • Why does it keep moving?
  • Why arent birds, clouds and other objects left
    behind?
  • He asked the same Questions regarding Ptolemys
    theory
  • His findings led Newton to his work on gravity

14
(No Transcript)
15
  • 1.5 KEPLERS THEORY
  • Brahe made a device that was so accurate that it
    is sometimes used today (0.04 degrees)
  • After 20 years of observations, he found that
    neither Ptolemy nor Copernicus was right
  • Kepler was Brahes disciple
  • Each planet moves in a sun-focused ellipse An
    ellipse having the sun at one of its two focuses

16
Keplers First Law The orbital paths of the
planets are elliptical (not circular) with the
Sun at one focus. What is an ellipse?
17
In-class Problem (a) A circle can be defined as
the set of all points that are equidistant from
the center point, i.e., all the points are the
length of the radius away from the center . How
can one define an ellipse in terms of the lengths
of string indicated in the figure?
(b) The separation of the two foci determines the
ellipticity ( or the out of round) of the
ellipse. How can one make a circle out of an
ellipse by changing the positions of the foci?
A
B
HINT for (a) the string does not stretch.
18
Perihelion and Aphelion of a planetary orbit
Perihelion point of closest approach. Aphelion
point at the greatest distance from the sun
19
Keplers Second Law (addressing the speed of a
planet along its elliptical path) An imaginary
line connecting the Sun to any planet sweeps out
equal areas of the ellipse in equal intervals of
time.
20
1.4 Copernicuss Theory A Sun-Centered Universe
Once Galileo had invented the telescope, he was
able to observe the phases of Venus. These phases
are totally incompatible with the Earth-centered
universe.
21
  • 1.6 DIALOGUE BETWEEN NATURE AND MIND
  • Figure 1.25 shows the dynamic interplay between
    observations and theories

22
When the last three planets were discovered
(Uranus, Neptune and Pluto), their orbits
followed closely Keplers theory
23
  • OBSERVATIONS Data-gathering
  • MEASUREMENT Quantitative observation
  • EXPERIMENT Observation designed and controlled
    by humans
  • THEORY Confirmed framework of ideas that
    explains or unifies a group of observations
  • MODEL Theory that can be visualized
  • No scientific idea is ever certain.

24
  • There are two common misconceptions about
    scientific knowledge
  • (a) Knowledge is absolute
  • (b) Knowledge is dubious guesswork
  • Knowledge is not absolute
  • (a) Ptolemys and Copernicus theories were not
    absolute but they served their purpose.They
    predicted planetary motion to within 10
    arc-minutes
  • (b) Keplers theory is not perfect
    either.planets severely deviate from their
    elliptical paths due to gravity between different
    planets.but is a good and useful
    approximation...

25
  • Science is not dubious guesswork
  • (a) People who disliked Copernican theory on
    religious or other grounds argued that it was a
    mere theory.They did not use scientific facts
    to disprove it.
  • (b) Imperfection of Earth meant that humankinds
    centrality to Gods plan was threatened. The
    catholic Church, for example, pronounced his
    theory as false, erroneous and heretical.
  • (b) Only until 1992 that the Pope announced that
    the Church had wrongly accused Gallileo.
  • (c) People that dislike the theory of evolution
    do the same.

26
  • Scientific Method The dynamic interplay between
    experience and thought
  • Scientists generally believe in the Pythagorean
    ideal of a universe based on simple and elegant
    principles

27
  • 1.7 Copernican Revolution
  • Roots of the scientific age
  • Pythagorean belief in natural harmonies the
    universe is organized in a framework of
    principles that can be uncovered by observation
  • Copernican revolution the Earth is a planet
    similar to the other planets, and the natural
    world is fundamentally the same everywhere

28
Some of the things we know today
  • Rejection of the geocentric illusion that Earth
    is at the center of the universe
  • The sun is a star
  • There are 400 billion visible aggregation of
    stars
  • Each of the giant aggregation of stars is called
    a galaxy
  • Ours is the Milky way

29
Relative Sizes of the Sun and the planets
30
An astronomical unit the average distance between
Earth and the Sun 149,600,000 km.
31
A primary reason for you to learn science,
according to the textbook's opening section, is
(a) to pass on Western culture to the next
generation. (b) to increase your intelligence.
(c) to increase your awareness. (d) because a
broadly educated person can get a better job.
(e) Actually there is no good reason all this
scientific nonsense.
32
Our primary reason for studying the theories of
Ptolemy, Copernicus, and Kepler was (a) to learn
some history of physics and astronomy. (b) to
learn about the methods and the validity of
science. (c) as a foundation for our later
study of Newtonian physics. (d) to see how
these early theories of atomic physics compare
with more recent studies. (e) so that we can
understand the structure of our solar system.
33
The most significant difference between the
astronomical theories of Ptolemy and Copernicus
is (a) Ptolemy's is not based on scientific
evidence, while Copernicus's is. (b) Ptolemy
uses circular planetary orbits while Copernicus
uses elliptical orbits. (c) Ptolemy's theory is
sun-centered, whereas Copernicus's is
Earth-centered. (d) Ptolemy's theory is
Earth-centered, whereas Copernicus's is
sun-centered. (e) Ptolemy's theory does away
with many of the complexities of the Copernican
theory.
34
The closest planet to the sun is (a) Pluto (b)
Earth (c) Jupiter (d) Mercury (e) Venus
35
Which statement best describes the status of the
Copernican and Ptolemaic theories of the solar
system shortly after Copernicus invented his
theory about 1550, and before Tycho? (a)
Copernicus had proved that Ptolemy's theory was
incorrect. (b) Both theories agreed with the
experimental facts. (c) Ptolemy's theory fit
the experimental facts better than the Copernican
theory. (d) although Copernicus couldn't
disprove Ptolemy's theory, the Copernican theory
agreed much better with the experimental facts
than did the Ptolemaic theory. (e) both
theories were known to be wrong.
36
Continuing the previous question, which of the
following statements best describes the status of
these two theories shortly after Tycho Brahe's
observations? (a) These observations showed
Ptolemy's theory to be the correct one. (b)
These observations showed Copernicus's theory to
be the correct one. (c) These observations
showed both theories to be correct. (d) These
observations showed both theories to be
incorrect. (e) These observations turned out to
have little or no bearing on either theory.
Write a Comment
User Comments (0)
About PowerShow.com