Chapter Three, Unit D Cycles in the Solar System

1. Chapter Three, Unit DCycles in the Solar System “Space: the final frontier…”

2. Science Question of the Day • Why is it hot in the summer and cold in the winter?

3. Answer

4. The Organization of the Solar System • The way we view the solar system has changed a lot over the years. • Astronomers used to believe that the Earth was the ___________ of the universe with everything revolving around it. • How self-centered of us!

5. The Organization of the Solar System • Ptolemy was the first to theorize a _________ model (and create a fairly well-working model) of how the planets, moons, and stars move in space. • He believed Earth was at the center and all other celestial bodies moved around us. • It wasn’t until much later that Copernicus developed a new theory (the _________ theory) of how planets rotate around stars like the Sun. • The problem with both Ptolemy and Copernicus’ theories was the way in which they described the motion of the planets as circular. • What’s wrong with this???

6. The Organization of the Solar System • The planets travel in an _________ (a flattened circle) around the Sun. • This was discovered by Kepler in the early 1600s. • This theory was not widely accepted until many years later, however, when Galileo was able to observe planetary motion with the telescope!

7. Planetary Motion

8. Planetary Motion

9. Science Question of the Day • Why does Saturn have rings?

10. Answer

11. The Structure of the Solar System • Our solar system isn’t just about planets and moons; there are also smaller bodies called _________, __________, and _______. • An _________ is a chunk of rock and metal that orbits the sun. • Asteroids are too small to be called planets, and lack the spherical shape that is characteristic of planets. • Many of the largest in our solar system are named and studied by NASA.

12. The Structure of the Solar System • Another body that is in our solar system is the _________. • Meteors are too small to be considered asteroids. • Meteors actually hit the Earth thousands of times a day! • Our atmosphere usually burns them up before they hit the Earth’s surface, but when one does survive and hits the Earth it is called a meteorite. • Many times we can see meteor showers at night.

13. The Structure of the Solar System • One other fun item we have in our solar system are ________. • Comets are balls of rock, ice, and frozen gasses that orbit the sun. They are different than asteroids because asteroids are made of _______ and ______, not gasses. • When comets get close to the Sun, the heat causes the gasses to react and glow as well as melt some of the ice in the comet which makes it form a tail. • We can see many comets from Earth when they pass close to our orbit around the Sun.

14. Comets, Asteroids, and Meteors

15. Time for a little practice… • Read “Asteroids, Meteors, and Comets” and answer questions 1-5.

16. Science Question of the Day • What are black holes and how are they formed?

17. Answer

18. Astronomical Units and Light Years • The distances in space are gigantic! • You may think it takes a long time to get to Florida for your family vacation. That’s only a few hundred miles; try multiplying that times a million and then adding on some more to get to the Sun. • Think about how many miles are between us and the farthest planet in our solar system, Neptune. • How about from here to the closest Earth-like planet, Gliese 151 c which is ______ trillion miles away?!

19. Astronomical Units and Light Years • Instead of measuring in miles, we measure distances within our own solar system in ______________ units or AUs. • One AU is equal to the number of miles between Earth and the Sun, about 93 million miles. • This makes it easier to write. Consider this example: Mars is 1.52 AU from the Sun versus Mars is 142,000,000 miles from the Sun.

20. Astronomical Units and Light Years • The AU only works in our solar system, however. • Stars in other solar systems are millions of times farther than the Sun to Earth, so we would have to use pretty large figures to describe that. • Instead, we use a larger unit, __________ years, to measure distances outside of our solar system. • A light-year is the equal to the distance light can travel in a vacuum in one year, 5.9 million million miles. • Alpha Centauri (the closest star to our solar system) is 270,000 AU from Earth. It is easier to say it is 4.3 light years from Earth.

21. Light Years and Time Travel • The cool thing about light years is that it allows you to look into the past. • It takes 4.3 light years for light from Alpha Centauri to reach Earth, so when we look at the star, we are actually looking into the past 4.3 years.

22. Space, Distance, and Time

23. Let’s do some calculations! • We know that one AU is equal to about 93 million miles, so how many miles are the following planets from the Sun?

24. Time for a little practice… • Read “Measuring Distance in the Universe” and answer questions 1 and 2 only.

25. Science Question of the Day • There is a definite beginning of time, therefore, there was something before the beginning. What do you think was before the beginning of the beginning?

26. Answer

27. The Cycles of Planets: Axes Rotation • Imagine if there were no rotation of our planet. What would it be like???

29. OR…

31. The Cycles of Planets: Axes Rotation • Imagine waking up in the morning to a black sky and and it continued month after month until finally the sun began to rise. The only problem is, the sun will now shine endlessly for months on end. • This may sound fun, but think of the heat and drought this will cause. • Not to mention how hard it will be to fall asleep with the sun streaming in! • This is what the world would be like if it did not __________.

32. Earth’s Rotation • Because of Earth’s rotation on its _______, we have a day that lasts about 24 hours. • The Earth’s axis is an imaginary line through the planet’s center from the ________ pole to the ________ pole. • The rotation causes the Earth to ________ through daylight and dark areas. • Every planet rotates on its axis, but they all rotate at different speeds.

33. Days and Years on Planets • Even though our days are 24 hours, other planets rotate faster or slower making their days shorter or longer. • Jupiter, for example, has a day that lasts only ________ hours. • Venus, however, has a day that lasts as long as ________ Earth days. That is 5,832 hours!

34. Days and Years on Planets • Planets not only rotate on their axes; they also _______ around the Sun. • Revolution is the movement of one object around another. • An orbit is the path an object follows in its __________. • The time in which it takes a planet to take a spin around the Sun is one year, but every year is different depending on the planet and how fast it travels around the Sun. • Kepler discovered that the farther you are from the Sun, the slower the planets speed in revolution.

35. Days and Years on Planets • For example, Neptune is the farthest planet from the sun, and it takes it _________Earth Years to travel in its elliptical orbit around the Sun. • The closer you are to the Sun, the faster your revolution will be. Mercury makes its way around the Sun in _______ Earth days.

36. Planetary Motion: Rotation and Revolution

37. Orbits (not the gum) • Planets travel in an ellipse around the Sun. • The Sun is not at the center of the ellipse, however, so that means that at certain points in a planet’s revolution it will be closer to the Sun than at other times. • When it is at the closest point to the Sun in its orbit, it is at the perihelion. • When it is at the farthest point to the Sun in its orbit, it is at the aphelion.

38. Orbits • Even though the Earth is sometimes closer to the Sun than other points in time, this is not what causes the seasons. • We are actually closest to the Sun during mid-winter in the northern hemisphere. • The seasons are caused by the Earth’s tilt in its axis as we discussed earlier in this unit.

39. Why an ellipse? • Let’s think about the first law of motion for a minute… • How does this effect the planets revolving around the Sun?

40. Why an ellipse? • The law states that an object in motion will stay in motion unless another outside force acts upon it. • The planet is being propelled through space because of _______, but the Sun’s gravitational pull changes the motion and pulls it back. • The inertia combined with _______ causes it to move in a curved path rather than a straight line.

41. Planets Wobble on Their Axes • We have discussed two ways in which the planets move (rotation and revolution), but we are missing the last piece to our puzzle: _________. • Precession is the wobble the Earth experiences every 26,000 years. • The Earth is constantly moving like a top, but we don’t notice it because it happens so slowly. • We know it does happen because our North Pole Star changes every 26,000 years.

42. Planets Wobble on Their Axes • Currently, our axis points to a North Star called ________. • Because of its location, Polaris doesn’t seem to move as Earth rotates. It appears to stay in one spot while all the other stars seem to move around it in fixed circles. • Because it seems to never move, navigators use it to help guide them. • Since we wobble, our North Star changes. • During the time of the Ancient Egyptians it was Thuban. • In the future, the North Pole star will be Vega.

43. Science Question of the Day • What do you think the Great Red Spot is on Jupiter?

44. Answer

45. Seasons and Climate on Earth • We know that Earth has seasons because at times it is tilted toward and away from the Sun and can absorb more or less energy and light. • If the Earth were to _______ on a vertical axis, the seasons would be the same year round. • Because of axial ______, the angle that a planet’s axis is tilted from a vertical point, the Sun’s rays are more intense at different points.

46. Overview of the Seasons • Summer • Tilted _______ the Sun • More direct rays • ______ days • Heats atmosphere

47. Overview of the Seasons • Fall • Axial tilt neither _________ or _______ from Sun • Sunlight angle less direct than in Summer • Daylight and dark are almost equal • Temperature begins to cool

48. Overview of the Seasons • Winter • Northern hemisphere pointed _______ from Sun • Sun’s rays are slanted and indirect • _______ hours of daylight • Climate grows cooler

49. Overview of the Seasons • Spring • Similar to Fall • Axial tilt neither _______ or ________ from Sun • Rather than progressively growing cooler, the climate becomes warmer

50. Seasons and Climates on other Planets • Earth has an orbit that is very close to ________, but other planets have more elliptical orbits. • This effects their climate either making it warmer when it is at its perihelion, or cooler when it is at its aphelion. • Planets also have tilts which can cause extreme seasons, or no season change at all.