1. Ptolemaic theory
(geocentric)
Copernicus’s theory
(heliocentric)

2. Theories about the center of the universe
A theory is an explanation of related observations.
Geocentric
EARTH centered
(sun, moon, stars, planets revolve around Earth)
Believed until 1500 AD
Early cultures and Ptolemy
Heliocentric
Sun centered
(planets and comets revolve around the sun)
1500 AD ~ present
Copernicus*, Galileo, Kepler, Newton
Are either correct? - Helio is mostly correct

3. Review Question
What did the geocentric theory state? Is this theory correct?
>>Earth is at the center of the solar system
(incorrect)

4. Big Bang Theory (theory of the formation of the Universe --1950)
BrainPop: Big Bang
matter, time, and energy were compressed into an extremely small ball(very unstable) also called a singularity, then exploded about BILLION years ago, this explosion is called a Supernova
The leftovers from the supernova is called a nebular cloud. It contains the gas & dust particles from the explosion, and is expanding outward
DYK: Every hour the Universe expands by a billion miles in all directions.

5. Nebular Theory
The most widely accepted theory on solar system formation is the NEBULAR THEORY
States that the solar and stellar systems were developed from an ancient nebula due to the process of accretion.
Protostar

6. Planetesimals form due to the accretion (clumping together)
Nebular Theory
remember, nebulae develop from supernovas
called a star when fusion begins in core (about 10m°K)
Stars begin as a protostar (baby star) in a nebula (gas/dust cloud from old stars)
Planetesimals form due to the accretion (clumping together)
of dust/gas particles that are in orbit around a protostar, eventually forming a planet
Protostar

7. …after about 10 billion years, the star becomes a MAIN SEQUENCE star, where it spends most of its life
this is the stage that our sun is in
(as well as most stars)
hydrogen changes to helium (nuclear fusion) in the core of the star

8. Rotation=SPIN (1 rotation=1 day=24 hours)
The axis of Earth is an imaginary line that runs through the middle of the Earth from the North Pole to the South Pole which Earth rotates or spins around
Earth is tilted on its axis at 23.5 degrees
(why we have seasons)
Day/night animation:

9. N I G H T D A Y

10. Revolution= movement around one object by another object
Note: all of our
planets revolve
counter~clockwise
around the Sun
orbit is the
PATH the planet
(or moon) takes
as it revolves
shape of orbit is
circular or elliptical (oval)
Ex: one revolution/orbit around the sun=1 year= days
Ex: one revolution/orbit of the moon around the Earth=1 month

11. GRAVITY depends on: MASS and DISTANCE INERTIA
Newton's First Law of motion states that an object will remain at rest or in motion (same direction) unless acted upon by an outside force.
elliptical
INERTIA
GRAVITY depends on:
MASS and DISTANCE
BrainPop: Newton

12. Earth in Space Earth revolves rotates On its axis Around the sun
Resulting in
Years
Day & night

13. Earth in Space March=Vernal Equinox September=Autumnal Equinox
BrainPop: Seasons
March=Vernal Equinox September=Autumnal Equinox
June=Summer Solstice December=Winter Solstice

14. Our Solar System (includes the sun, 9 planets and their moons, asteroids, comets, meteoroids & other smaller objects)

15. Our star, THE SUN yellow middle-aged (main sequence) medium-sized
surface temperature of about 6000°C
medium brightness

16. SUPERGIANTS
(on Orion’s shoulder)
GIANTS

17. Planets Inner Planets Outer Planets Other…
also called terrestrial planets
small, dense and rocky
no rings
Mercury
Venus
Earth
Mars
Outer Planets
also called gas giants or Jovian planets
all have moons
all have at least one ring
Jupiter
Saturn
Uranus
Neptune
Other…
Pluto (reclassified as a dwarf planet)

18. Relative size of the planets

19. Comets ~small body of ice, rock, and cosmic dust
~ look like “dirty snowballs”
~tail visible when comet gets close enough to the sun (points away from sun due to solar winds) ~tail can be millions of miles long, and seen for many weeks
~gets smaller with every trip (melts)

20. …website animation…
(comet passage)

21. You can see a comet for weeks (or months)! …unlike a meteor

22. Asteroids
dense, rocky bodies that orbit the sun (over 100,000 known)—smaller than a planet
most are irregularly shaped (not round)
size: few meters to 900 km
most found in the asteroid belt (between Mars and Jupiter)

23. Ceres largest known asteroid (785 km) now considered to be a dwarf planet

24. Meteoroids Meteoroid= small pieces of comets or asteroids in space
Meteor= burning up in the atmosphere
(inaccurate to say “falling/shooting star”)
Meteorite= hits the ground (MAY make a crater)

25. WOW!!! Meteor shower over Russia, Feb 15, 2013

26. Which one is this? What caused this?
meteor
meteorite

27. Did you know??
The mass of the earth increases every year because of the 3,000 TONS of meteorite debris that hits the surface from space!
Approximately every years, somebody is struck by a meteor; last time was in 1954
The odds of you being hit is a billion to one (no human has ever been killed by a meteor strike).

29. Think about it….
If we were to send a manned mission to Mars, how could we avoid getting damaged by the asteroid belt?
The asteroid belt is between Mars and Jupiter.
If you lived on the moon, about how many meteors would you see on the moon in an earth year?
None—no atmosphere

30. Which of the following is a characteristic of comets?
A. Comets are composed of rocky material, iron, and nickel.
B. Comets follow a circular orbit around the sun.
C. Comets give off gas and dust when heated by the sun.
D. Comets are rich in iron.

31. Which of the following is a wide region of small, rocky bodies that is located between the orbits of Mars and Jupiter?
A. the Kuiper belt
B. the Oort cloud
C. the asteroid belt
D. the rings of Saturn

32. When it approaches the sun, which object produces a shimmering tail that lasts at least a few days?
a comet
In which direction does a comet’s tail always face?
away from the sun

33. Where are most asteroids found?
in orbit between Mars and Jupiter
What is the sequence that describes a space rock that falls to Earth’s surface?
meteoroid, meteor, meteorite

34. Which one of the following objects in our solar system would travel the greatest distance during one revolution around the sun?
A. a terrestrial planet
B. an asteroid
C. a gas giant
D. a comet