2. ASTRONOMY
• defined as the study of the objects
that lie beyond our planet and the
processes by which these objects
interact with one another.
3. HOW GREEKS KNOW THAT THE EARTH IS ROUND
• Aristotle (384-322 BCE) - the tutor of Alexander the Great,
describes how the progression of the Moon’s phases – its
apparent changing shape – results from our seeing different
portions of the Moons sunlit hemisphere as the months goes by.
He also knew that the sun has to be further away than is the
moon because occasionally the Moon passed exactly between
Earth and the Sun and hid the sun temporarily from view. We
call it a Solar Eclipse. A Lunar eclipse occurs when the moon
moves into and out of Earth’s shadow.
6. ARISTOTLE’S TWO CITED ARGUMENT THAT EARTH IS ROUND
- First is the fact that as the Moon enters or emerges from
Earth’s shadow during an Eclipse of the Moon, the shape of
the shadow seen on the Moon is always round. Only a
spherical object always produces a round shadow.
- Second, Aristotle explained that travelers who go south a
significant distance are able to observe stars that are not
visible farther north. And the height of the North Star – the
star nearest the north celestial pole- decreases as the
traveler moves south.
7.
8. HOW GREEKS KNOW THAT THE EARTH IS ROUND
• Eratosthenes (276-194 BCE) - a
Greek Mathematician living in
Alexandria, Egypt. His method
was a geometric one, based on
observations of the Sun. In
order to know the size of the
Earth, he measured the shadow
of Alexandria and Syene to
calculate their angle relative to
the sun.
9. HOW GREEKS KNOW THAT THE EARTH IS ROUND
• Eratosthenes said that no vertical shadow was cast as the sun
rays fall vertically in the city of Syene in Egypt during summer
solstice. Eratosthenes noted that all same time a shadow was
cast as the sun rays fell at an angle of 7.2 degrees [one fiftieth
(1/50) of a circle of ancient Greek writings] in the city of
Alexandria. He assumed that the sun was so distant that the
rays fall parallel to each other on the Earth’s surface and that
the difference in the shadow was cast in the two cities was due to
the curvature of Earth’s round surface.
10. ASTRONOMICAL EVENTS KNOWN TO MEN BEFORE THE ADVENT OF
TELESCOPES
• Diurnal Motion – is defined as the apparent daily motion of stars
and other celestial bodies across the sky due to Earth’s rotation.
The Greek astronomers have described ‘fixed stars’ moving in the
sky at the same arrangement and speed as most of the stars are.
Stars whose movements deviate from what seems to be fixed
stars were called ‘planetes’ which means ‘wandering stars’ in
Greek. The seven wandering stars are the Sun, Moon, Mercury,
Venus, Mars, Jupiter, and Saturn.
11. ASTRONOMICAL EVENTS KNOWN TO MEN BEFORE THE ADVENT OF
TELESCOPES
• Annual Motion – is the apparent yearly motion of
stars and other celestial bodies across the sky due to
Earth’s revolution. Below are events under annual
motion.
A. Zodiac and the Ecliptic – If we trace the path the sun takes in
the celestial sphere as we see on Earth, we would have traced the
ecliptic. A band of thirteen constellations collectively called zodiac
can be seen in the ecliptic. These constellations served to mark the
time for planting and used by astronomers to develop a chart called
horoscope.
12.
13.
14.
15. ASTRONOMICAL EVENTS KNOWN TO MEN BEFORE THE ADVENT OF
TELESCOPES
B. Equinoxes and Solstices – Equinoxes are the two days in a year
in which the sun crosses the celestial equator occurring near March
20 (vernal equinox) and near September 22 (autumnal equinox).
Midway between these two equinoxes is the solstices. Solstices are
the two days in a year in which the sun is at the farthest
declination (north or south) from the celestial equator.
16. ASTRONOMICAL EVENTS KNOWN TO MEN BEFORE THE ADVENT OF
TELESCOPES
C. Precession – Hipparchus in 150 BCE has discovered based on
his observation that the north celestial pole has changed during the
period of a half-century. He noticed that the slow and continuous
change in the direction in which the sky is moving.
D. Eclipse – occur when either the Earth or moon cast a
shadow into each other. A solar eclipse occurs when the moon
passes between the Earth and sun with the moon casting a
shadow on the Earth’s Surface. A lunar eclipse occurs when
the Earth is directly aligned between the sun and the moon
with the Earth casting a shadow on the moon.
17. HOW GREEKS KNOW THAT THE EARTH IS ROUND
• Tycho Brahe – a Danish Astronomer, nobleman and writer born
the Danish Peninsula of Scania and is known for his accurate
observations of the movement of celestial bodies. He invented
different astronomical instruments, with help of his assistant,
and made an extensive study of the Solar system. He, together
with his assistants were able to determine the position of 777
fixed stars accurately.
18. HOW GREEKS KNOW THAT THE EARTH IS ROUND
• Johannes Kepler – a German Astronomer, mathematician, and
astrologer moved to Prague in 1599 where he was supported by
Emperor Rudolf II. He then works as an imperial mathematician
and work as an assistant of Tycho Brahe at the age of 27. Kepler
was born to a poor German family, and studied as a scholar at
the University of Tubingen in 1589. He considered the key figure
in the 17th century scientific revolution. He was known for his
Laws of planetary motion and published books.
19.
20. KEPLER’S LAW OF PLANETARY MOTION
1. The Law of Ellipses
- Describes that the actual path followed by the planets was elliptical, not circular,
with the Sun of one focus of the ellipse.
2. The Law of Equal Areas
- States that when an imaginary line is drawn from the center of the Sun to
the center of the Planet, the line will sweep out an equal area of space in
equal time interval.
3. The Law of Harmony
• Unlike the first and second laws that describe the motion characteristics of
a single planet, the third law makes a comparison between the motion
characteristics of different planets,
21. GALILEO’S ASSERTION AND NEWTON’S LAW OF
MOTION
GALILEO GALILEI
- was a very famous astronomer,
engineer, and physicist. He is
popularly known as the father of
observational astronomy. His most
noteworthy discovery was that the
Earth revolves around the sun.
22. GALILEO’S UNIFORM ACCELERATION
• Galileo asserted using his cannonball
experiment that when objects are dropped
simultaneously at the same height, they will
reach the ground at the same time regardless
of mass, size, and air resistance. This
experiment paved the way for the discovery
of the principle of uniform acceleration.
23.
24.
25. NEWTON’S LAW OF MOTION
ISAAC NEWTON
- Isaac Newton was a physicist
and mathematician who developed
the principles of modern physics,
including the laws of motion and is
credited as one of the great minds
of the 17th-century Scientific
Revolution.
26.
27. REFLECTION AND REFRACTION OF
LIGHT
WHAT IS REFLECTION OF LIGHT
Reflection of light (and other forms of
electromagnetic radiation) occurs when the waves
encounter a surface or other boundary that does not
absorb the energy of the radiation and bounces the
waves away from the surface.
28. REFLECTION OF LIGHT EXAMPLE
• The simplest example of visible light reflection is the
surface of a smooth pool of water, where incident light
is reflected in an orderly manner to produce a clear
image of the scenery surrounding the pool. Throw a
rock into the pool (see Figure 1), and the water is
perturbed to form waves, which disrupt the reflection
by scattering the reflected light rays in all directions.
29.
30. REFLECTION AND REFRACTION OF
LIGHT
WHAT IS REFRACTION OF LIGHT
- Refraction of light refers to when light travels in a single
direction, it follows a straight path while when it bends.
- Refraction in simple terms is the bending of light when it
passes from one transparent substance to another. It also
happens with water, sound and other waves. Due to this
bending, which causes refraction of light, we are able to
have magnifying glasses, prisms, lenses and rainbows.
31.
32. WHAT IS PHOTON?
• A photon is a particle of light defined as a discrete bundle
(or quantum) of electromagnetic (or light) energy. Photons
are always in motion and, in a vacuum (a completely
empty space), have a constant speed of light to all
observers. Photons travel at the vacuum speed of
light (more commonly just called the speed of light) of c =
2.998 x 108 m/s.
33. THREE QUANTITIES OF PHOTON
- C = speed of light (2.998 x 108m/s)
- Λ = photon wavelength
- F = photon frequency
34. HOW TO CALCULATE THE ENERGY OF
PHOTON
E = hc / Λ
E = energy of the photon
c = speed of light (2.998 x 108m.s-1)
Λ = photon wavelength
f = photon frequency
h = the Planck’s constant (6.626 x 10 -34 J s)
35. EXAMPLE 1
Calculate the energy of a photon of radiation that
has a wavelength of 3.3 x 10-6 m
36. EXAMPLE 2
Calculate the energy of a photon of radiation that
has a wavelength of 4.6 x 10-14 m
37. QUIZ (5 POINTS EACH)
Calculate the energy of a photon of radiation that
has a wavelength of 4.7 x 10-16 m
Calculate the energy of a photon of radiation that
has a wavelength of 3.9 x 10-10 m
