Physical Science: Week 1 Topic 1 - Know the Universe

1. KNOW THE
UNIVERSE
• How the Greeks Knew that the
Earth is Spherical
• Astronomical Phenomena Known
to Astronomers before the Advent
of Telescope
• Brahe’s Innovation

2. OBJECTIVES
Explain how the Greeks knew that the Earth is spherical (S11/12PS-
IVa-38)
Explain how Brahe's innovations and an extensive collection of data
in observational astronomy paved the way for Kepler’s discovery of
his laws of planetary motion (S11/12PS-IVb-44)
Cite examples of astronomical phenomena known to astronomers
before the advent of telescopes (S11/12PS-IVa-41)
01
03
02

3. Who believes
that Earth is
spherical?

4. MESOPOTAMIAN
S
Described Earth as a
flat disk floating in
the ocean and
bounded by a
spherical sky.

5. As quest of knowledge continues and civilization
prosper, several models of universe presented

6. He argued that:
• The sphere is perfectly solid and the
heavens are a region of perfection.
• The earths component pieces, falling
naturally towards the center, would
press into a round form.
• In an eclipse of the moon, the Earth's
shadow is always circular thus, if
Earth is a flat disc, it would cast an
oval shadow
• Even in short travels northwards the
Pole Star is higher in the sky
ARISTOTLE

7. Another phenomenon considered by
Greeks in their claims: NAVIGATION
They observed that when ships sails away, it seems that it
gradually disappears behind the horizon.

8. Astronomical
Phenomena

9. • Change within 29.5
days.
• Changes appearance
from a thin semi-
circular disk to a full
circular disk.
• Periodic change of the
moon’s phases was
the basis of ancient
calendar.
PHASES OF THE
MOON

10. • The time in a month
when the moon or
part of it seemed to
be covered by a
shadow for a brief
moment.
• Occurs when Earth
is between the moon
and the Sun, Earth
casts a shadow on
the moon.
LUNAR ECLIPSE

11. • Happens when the
moon is in between
the Sun and the
Earth and the moon
partially or
completely blocks
out the Sun.
SOLAR ECLIPSE

12. • The astronomers
noticed that the
constellations’ positions
in the night sky vary
depending on the time
of the year.
• The stars seem to be
attached to a celestial
sphere that rotates
around an axis in one
day.
MOTION OF THE
STARS

13. • Few stars in heaven are
relatively brighter than
the rest of the stars.
• Seemed to be fixed in
their position but these
stars change position
periodically thus, it is
call “wanderers” or
planets
VISIBILITY OF
PLANETS

14. Brahe’s
Innovation

16. GEOHELIOCENTRIC
MODEL
• A hybrid of the
geocentric model
and heliocentric
model.
• The sun orbited the
Earth, while other
planets orbited the
sun.

17. ORBIT OR LAW OF
ELLIPSE
The planets move
in elliptical orbits
with the Sun at a
focus (F1). The
other focus (F2) is
empty.

18. LAW OF EQUAL AREAS
• As the planets
orbit around the
sun, the planets
cover equal areas
in equal times.

19. LAW OF PERIODS
The ratio of the squares of the
periods (the time needed for
one revolution about the Sun)
of any of the two planets
revolving around the Sun is
equal to the ratio of the cubes
of their mean distances from
the Sun