Transcript 9 Science Chapter 10 Revised 2015x

What we know about the universe has taken us
thousand of years
Celestial Bodies
 Celestial Body: a natural object out in space
such as a planet, a moon, an asteroid, a comet, or a
star
 Star: like our sun, give off heat and light and
are thousands of years away
 Planets: a celestial body that orbits one or more
stars, is large enough that its own gravity holds it
in a spherical shape, and is the only body
occupying the orbital path.
Constellations
Constellations
 Constellations: a distinctive pattern in the night
sky formed by a group of stars. It often looks
like a familiar object like an animal.
 Examples: Ursa Major or the great bear, Ursa
Minor or the little bear, Orion the hunter,
 Asterisms: smaller groups of stars forming
patterns within the constellations. Example: the
big dipper (found in Ursa Major)
Ursa Major
Orion
Orion is one of the brightest
constellations and is a
mythological character
According to Greek
myths, Orion was a
hunter who used to
brag all the time.
This bother the gods.
When the gods
were tired of him,
the sent a scorpion
to bite and kill him.
The gods felt bad for
doing having Orion
killed, they placed him
in the sky
Ursa Minor
Motion of Cellestial bodies
 Sun follows the same path through the sky
everyday and the path is called ecliptic.
 Ecliptic:
the path followed by the Sun through the
sky, as seen from Earth.
Apparent path of the Sun as
seen from Earth
Motion of planets
 They follow an ecliptic path called orbits around
the Sun,which are long, slightly flattened circles.
 These orbits result from gravitational forces
 As the Earth revolves around the Sun, it appears
that the Sun is moving against the background of
stars
 As the planets revolve around the Sun, they move
at different rates along an ecliptic path
depending on their distance from the sun
Planet motion
Motion of Planets
 Those inside Earth’s orbit (Mercury and Venus)
appear to race through the sky and appear to be
close to the Sun
 Those beyond Earth’s orbit are slower (Mars) and
appear far from the Sun in the sky. Seem to move
against the background of stars in the sky
Motion of Asteroids and
Comets
 Both Orbit around the sun
 Asteroids: one of many small rocky bodies in our
solar system, most of which orbit the Sun
between Mars and Jupiter.
Comet orbit
 The orbits of comets can be above
or below the orbit of Earth, for this
reason we do not always see the
comet on the ecliptic
 They can orbit in different planes
(unlike all other planets)
 Visit to explore the orbits of comets
and asteroids
www.spaceplace.nasa.gov/en/educators/
comet_orbits_cnsr.pdf
Comets Orbit the Sun
Motion of the Moon
 The moon orbits around Earth once every 28 days.
Other motion..
 Planets, suns (stars) and moons spin on a central
axis. Earth spins on its axis, which is an
imaginary line from the North Pole to the South
Pole
 Remember:celestial bodies move in cyclic paths called
orbits and that these orbits result from gravitational
forces.
 Example: the Earth spins on its axis towards the
east. Stars, including the Sun, all generally move
from east to west.
Early Models and Evidence Gathered about the
Universe
 Aristotle: saw the universe as
geocentric – the Earth at the center
and the sun, moon, planets and
stars revolving around it.
 Patterns of stars does not change so
he thought the Earth was in a fixed
place
 During a lunar eclipse, the shadow
cast on the moon had curved edges
so Earth must be a sphere.
Aristotle’s Evidence that
Earth is Sphere
Early models…
Ptolemy: He noticed that the motion of Mars in
the sky over several weeks creates a loop in the
sky. This change in direction is called retrograde
motion.
Early models…
 To explain this motion, Ptolemy proposed that
each planet revolved around a point on its orbit,
called an epicycle, to explain its motion through
the heavens
Early models…
 Copernicus: he thought
the earlier observations
could be explained in a
simpler way by a model
in which Earth rotated
on its axis once daily and
revolved around the Sun
once a year.
(Heliocentric model)
 The Earth’s motion
around the Sun is
relatively recent (1543)
 Galileo: First person to turn a small telescope
towards the sky and publicly report what he saw.
 Observed craters on the moon, spots on the sun,
and four “stars” orbiting Jupiter.
 Galileo also observed that Venus had phases like
our moon does and this could only happen if Venus
orbited the Sun
 Johannes Kepler: with the help of Tycho Brahe,
made observations of Mars’ orbit and found that it
modeled an ellipse (oval shape)
 Kepler developed three laws of planetary motion
Sir Isaac Newton
 He was the first to show mathematically that the
force of gravity reaches far beyond the surface
of Earth and affects all celestial bodies
 This force causes the bodies to remain in orbit
around larger bodies
 Invented the reflecting telescope which allowed
more precise observations.
Early Technologies for
observations
 Stone Circles: possibly used to make simple
astronomical observations. For example,
Stonehenge. On midsummer’s day the Sun rises
directly over a particular stone in Stonehenge.
Marking the longest day of the year.
Sun rising over a stone
Early Technologies…
 Astrolabe: around the time
of Ptolemy, they were used to
help locate and predict the
positions of the Sun, Moon
and stars
 Using a compass and an
astrolabe, they were able to
describe the position of any
celestial body in relation to
the direction North as well as
in relation to the horizon.
 ASTROLAB ACTIVITY:
http://cse.ssl.berkeley.edu/A
tHomeAstronomy/activity_07
.html
Technologies…
 Telescope: Refracting telescope (uses lenses to
gather and focus light) was used by Galileo to
make his observations (Sun centered universe)
 Reflecting Telescope: (uses mirrors to gather
and focus light) was developed by Newton to make
even more precise observations and this design is
used today, called the Newtonian design
Core Lab
 Strolling Through the Solar System