1. Birth of a Solar System Birth of a Solar System Chapter 17, Section 1

2. 1.Let’s review Gravitational Pull

4. Investigate Lab: Analysis 4  Both pieces of paper should reach the bottom at the same time when the flat piece of paper is placed on a book.  They should have fallen at the same rate as the book. Gravity causes all objects to fall at the same rate, regardless of their mass.  Both pieces of paper should reach the bottom at the same time when the flat piece of paper is placed on a book.  They should have fallen at the same rate as the book. Gravity causes all objects to fall at the same rate, regardless of their mass.

5. Investigate Lab: Analysis 5  The crumpled piece of paper should reached the floor first.  While gravity pulled both pieces toward the floor, the differing result has to do with air resistance.  The crumpled piece of paper should reached the floor first.  While gravity pulled both pieces toward the floor, the differing result has to do with air resistance.

6. 2. The Hammer & the Feather On the Moon

7. 3. Mythbusters : Feather & Hammer

8. What is gravity?  Gravity is a force of attraction between two objects.  Gravity gets stronger as objects get bigger and closer together.  The bigger the object, the more gravitational pull it will have on nearby objects.  The Earth is so big, that it is able to pull the pieces of paper to its surface.  Gravity is a force of attraction between two objects.  Gravity gets stronger as objects get bigger and closer together.  The bigger the object, the more gravitational pull it will have on nearby objects.  The Earth is so big, that it is able to pull the pieces of paper to its surface.

9. 4. Moon and Gravitational Pull Explained

10. How did our solar system come to be?  Today we are going to look at a theory created by scientists to explain how the solar system ever came to be.  We will talk about how the planets, including Earth, were formed.  What is a solar system?  A solar system is composed of the sun (a star) and the other bodies that travel around the sun.  Today we are going to look at a theory created by scientists to explain how the solar system ever came to be.  We will talk about how the planets, including Earth, were formed.  What is a solar system?  A solar system is composed of the sun (a star) and the other bodies that travel around the sun.

11. It all starts with a Nebula  A what?  A nebula is a huge interstellar cloud made up of dust and gas.  Nebulas are so big it takes many years to cross them.  These nebulas are cold (10 degrees above absolute zero) and dark.  A what?  A nebula is a huge interstellar cloud made up of dust and gas.  Nebulas are so big it takes many years to cross them.  These nebulas are cold (10 degrees above absolute zero) and dark.

12. Gravity Pulls Matter Together  These nebulas which consist of dust and gas have matter and therefore have mass.  However, the matter in a nebula is very spread out and because of this the attraction between the gas/dust particles is very small.  These nebulas which consist of dust and gas have matter and therefore have mass.  However, the matter in a nebula is very spread out and because of this the attraction between the gas/dust particles is very small.

13. Pressure Pushes Matter Apart  As the molecules in a nebula are pulled together by gravity, they begin to hit each other and bounce back.  These collisions create a push, or pressure, within the nebula.  As the molecules in a nebula are pulled together by gravity, they begin to hit each other and bounce back.  These collisions create a push, or pressure, within the nebula.

14. Together, gravity & pressure reach a balance in a nebula.

15. What is this lady talking about?  Ok, think of it like this.  What keeps you balanced on your chair?  Gravity pushes you down on the chair  The pressure of the chair pushes you back up.  Together, they balance each other out.  Ok, think of it like this.  What keeps you balanced on your chair?  Gravity pushes you down on the chair  The pressure of the chair pushes you back up.  Together, they balance each other out.

16. The Solar Nebula Forms  So we have this perfectly happy & balanced nebula.  Suddenly, out of no where, a neighboring nebula crashes into it! Ahhhh!  When that happens stars can explode and areas can become so compressed that pressure can ’ t react quickly enough to balance the gravity.  So we have this perfectly happy & balanced nebula.  Suddenly, out of no where, a neighboring nebula crashes into it! Ahhhh!  When that happens stars can explode and areas can become so compressed that pressure can ’ t react quickly enough to balance the gravity.

17. The Solar Nebula Forms  Enter: the solar nebula.  When nebulas collide and the balance is upset, a star may be formed in the middle of the dust cloud.  This star, now called a solar nebula, becomes the center of the new solar system.  Enter: the solar nebula.  When nebulas collide and the balance is upset, a star may be formed in the middle of the dust cloud.  This star, now called a solar nebula, becomes the center of the new solar system.

18. 5. Birth of a Solar System

19. The solar nebula changes  Once our solar nebula collapses, things happen quickly (on a cosmic scale!)  The dark clouds collapsed, matter in the clouds got closer and closer together.  The gas and dust particles moved at a faster rate.  The center of the cloud got hotter and hotter and hotter.  Once our solar nebula collapses, things happen quickly (on a cosmic scale!)  The dark clouds collapsed, matter in the clouds got closer and closer together.  The gas and dust particles moved at a faster rate.  The center of the cloud got hotter and hotter and hotter.

20. And it keeps changing…  Before you know it … the dust and gas begins to rotate slowly around the hot center and the solar nebula flattens into a disk.

21. 6. The Birth of a Solar System

22. Planetesimals Form  With so many collisions happening in this swirling vortex of cloud, bits of dust start sticking together.  This dust begins to form the building blocks of planets called planetesimals.  With so many collisions happening in this swirling vortex of cloud, bits of dust start sticking together.  This dust begins to form the building blocks of planets called planetesimals.

23. Planets Form  The biggest planetesimals collect more and more of the dust & gas and eventually become a planet.  Watch it all here! Watch it all here!  The biggest planetesimals collect more and more of the dust & gas and eventually become a planet.  Watch it all here! Watch it all here!

24. Inner & Outer Planets Form  The gas planets (or outer planets)- Jupiter, Saturn, Uranus and Neptune, were all able to collect a ton of dust in the cooler, outer solar nebula.  Once they grew large enough, their gravity was strong enough to attract the nebula gases, hydrogen and helium.  The rocky planets (or inner planets) - Mercury, Venus, Earth & Mars, couldn ’ t take the heat and all of the gases burned off, leaving only the rocky parts.  The gas planets (or outer planets)- Jupiter, Saturn, Uranus and Neptune, were all able to collect a ton of dust in the cooler, outer solar nebula.  Once they grew large enough, their gravity was strong enough to attract the nebula gases, hydrogen and helium.  The rocky planets (or inner planets) - Mercury, Venus, Earth & Mars, couldn ’ t take the heat and all of the gases burned off, leaving only the rocky parts.

25. What makes an inner planet different from an outer planet? Inner Planet  Rocky  Small  Thin atmosphere  Few or no moons  Molten core in Earth and Mars Inner Planet  Rocky  Small  Thin atmosphere  Few or no moons  Molten core in Earth and Mars Outer Planets  Mostly gas  Huge  Thick atmosphere  Many moons  rocky core  not dense

26. 7. Journey to the Edge of the Universe

27. Let’s Talk: Planetary Motion  We have one more thing to talk about today and it is …  What is planetary motion?  It is how the planets move.  We have one more thing to talk about today and it is …  What is planetary motion?  It is how the planets move. revolution

28. Weird Science  When you consider the motion of the Earth ’ s rotation, it ’ s revolution around the sun, and the sun ’ s movement around the Milky Way galaxy, you are actually traveling more than 900,000 km/h just standing still!

29. Planetary Motion: Rotation  The Earth spins, or rotates, around its axis.  Only 1/2 of the earth faces the sun at any given time.  As the earth rotates, different parts of the Earth receive sunlight.  The half facing the sun is light (day), and the half facing away from the sun is dark (night).  The Earth spins, or rotates, around its axis.  Only 1/2 of the earth faces the sun at any given time.  As the earth rotates, different parts of the Earth receive sunlight.  The half facing the sun is light (day), and the half facing away from the sun is dark (night).

30. Planetary Motion: Rotation  Did you know we ’ re all a little crooked??  The Earth ’ s axis is tilted 23.5˚.  The Earth also rotates very quickly - 1000 miles per hour!  How long does it take the Earth to complete one rotation (or one spin around its axis)?  1 day, or 24 hours.  Did you know we ’ re all a little crooked??  The Earth ’ s axis is tilted 23.5˚.  The Earth also rotates very quickly - 1000 miles per hour!  How long does it take the Earth to complete one rotation (or one spin around its axis)?  1 day, or 24 hours.

31. Planetary Motion: Revolution  The Earth also travels around the sun in a path called an orbit.  The motion around the sun along its orbit is called a revolution.  The other planets ALSO revolve around the sun on their orbits.  The Earth also travels around the sun in a path called an orbit.  The motion around the sun along its orbit is called a revolution.  The other planets ALSO revolve around the sun on their orbits.

32. Planetary Motion: Revolution  How long does it take the Earth to revolve around the sun?  The Earth revolves around the sun in 365 days or 1 year.  We call this the period of revolution.  Make sure you know the difference between revolution & rotation!!!!  How long does it take the Earth to revolve around the sun?  The Earth revolves around the sun in 365 days or 1 year.  We call this the period of revolution.  Make sure you know the difference between revolution & rotation!!!!

33. Let’s Try it!  Whoever is the blondest person in your group is the:  SUN - stand still & shine!  The tallest person is the:  EARTH rotating around its axis and revolving around the sun - be a graceful ballerina!  The smallest person is the:  MOON rotating around its axis and revolving around the Earth - be calm and serene!  The last person:  Make sure they’re doing it right - be a bossy dictator!  Whoever is the blondest person in your group is the:  SUN - stand still & shine!  The tallest person is the:  EARTH rotating around its axis and revolving around the sun - be a graceful ballerina!  The smallest person is the:  MOON rotating around its axis and revolving around the Earth - be calm and serene!  The last person:  Make sure they’re doing it right - be a bossy dictator!

34. Question of the day  Why do we have seasons???

35. 8. Harvard Graduates should know!

36. 9. Let’s see if these kids know better!

37. Why do we have seasons???  Does the Earth get closer to the sun for summertime to occur????  NOOOOOOOOOOOOOOOOOOO  The placement of the Earth in orbit has NOTHING to do with seasons  The seasons are caused by the tilt of the Earth on its axis.  Does the Earth get closer to the sun for summertime to occur????  NOOOOOOOOOOOOOOOOOOO  The placement of the Earth in orbit has NOTHING to do with seasons  The seasons are caused by the tilt of the Earth on its axis.

38. Seasons & the Earth’s Tilt  Hey, didn ’ t I warn you that we ’ re all a little crooked?  In the summer, the Northern Hemisphere is tilted toward the sun.  In the winter, the Northern Hemisphere is tilted away from the sun.  In fact, Earth is actually closest to the sun during the Northern hemisphere ’ s winter.  Hey, didn ’ t I warn you that we ’ re all a little crooked?  In the summer, the Northern Hemisphere is tilted toward the sun.  In the winter, the Northern Hemisphere is tilted away from the sun.  In fact, Earth is actually closest to the sun during the Northern hemisphere ’ s winter.

39. Why are there seasons?  Of course, no one can explain it better than Tim & Moby.  BrainPOP: Seasons BrainPOP: Seasons  Of course, no one can explain it better than Tim & Moby.  BrainPOP: Seasons BrainPOP: Seasons