EEn Explain the Earth s motion through space, including precession, nutation, the barycenter, and its path about the galaxy.

Transcription

1 EARTH IN SPACE

2 EEn Explain the Earth s motion through space, including precession, nutation, the barycenter, and its path about the galaxy. I Can Explain the origin of the Earth s motion based on the origin of the galaxy and its solar system. Recall Earth s role in the hierarchy of organization within the universe and in the development of the continuum.

3 Explain planetary orbits, especially that of the Earth, using Keplar s laws. Explain relative motion of the Earth in the solar system, the solar system in the galaxy, and the galaxy in the universe - including the expanding nature of the universe; Orbital motion (Earth around Sun - once/year, seasons depend upon an approximate 23.5 degree tilt); Rotation around Earth s axis (day/night). Explain precession - change in direction of the axis, but without change in tilt - this changes the stars near (not near) the poles, but does not affect the seasons (as long as the angle of 23.5 degrees stays the same).

4 Explain nutation - wobbling around the precessional axis. This is a change in the angle - ½ degree one way or the other that occurs over an 18 year period and is due to the moon exclusively. This slightly increases or decreases amount of seasonal effects. Explain barycenter - the point between two objects where they balance each other. When a moon orbits a planet, or a planet orbits a star, both bodies are actually orbiting around a point that lies outside the center of the primary (larger) body. For example, the moon does not orbit the exact center of the Earth, but a point on a line between the Earth and the moon approximately 1,710 km below the surface of the Earth, where their respective masses balance. Summarize that the Sun is not stationary in our solar system. It actually moves as planets tug on it, causing it to orbit the solar system s barycenter. The Sun never strays too far from the solar system barycenter.

5 ENGAGE Prepare to have your mind blown. Our Home in the Universe

6 EXPLAIN - OUR SOLAR SYSTEM & THE MILKY WAY Our solar system is located in the Milky Way Galaxy. Galaxies are made up of many stars. Earth is a satellite planet of one particular star. our Sun. There are other stars in the Milky Way that have planetary systems similar to our solar system.

7 EXPLAIN - The Milky Way There is a Black Hole at the center of our Milky Way Galaxy. What if you jumped in a Black Hole? Spiral arms around the center contain mostly blue stars, gas and dust. There are blue stars and red stars in our galaxy. Blue stars are young and hot stars. Red stars are old and cool stars. The Earth is located in one of the spiral arms. The stars you can see at night with your naked eye are a part of the Milky Way galaxy.

8 EXPLAIN - OTHER GALAXIES and THE UNIVERSE The Milky Way is part of a cluster of about 30 other galaxies. These are all the other galaxies in the Laniakea Supercluster. The universe is made up of about 100 billion galaxies.

9 EXPLAIN - OUR CLOSEST NEIGHBOR The closest known galaxy to us is the Canis Major Dwarf Galaxy, at 236,000,000,000,000,000 km (25,000 light years) from the Sun. To get to the closest galaxy to ours, the Canis Major Dwarf, at Voyager's speed, it would take approximately 749,000,000 years to travel the distance of 25,000 light years! If we could travel at the speed of light, it would still take 25,000 years to travel there! Why do you think our knowledge about other galaxies is limited?

10 EXPLAIN: Observe the image and answer the following: 1. Describe at least two things you notice about the movement of the objects? 2. What does this image remind you of? 3. What is this motion called? 4. Can you explain how this happens?

11 EXPLAIN How do Orbits happen? Larger body has a strong gravitational pull on the smaller body (green, a arrow). Inertia is the straight, forward movement of the smaller body (red, v arrow). These two forces compromise and an orbital path is formed. What would happen if the Earth stopped moving forward? What would happen if the Earth lost its gravitational pull on the moon?

12 EXPLAIN - Earth s Rotation One rotation about the Earth s axis takes 24 hours. This is called a day. Rotation about the Earth s occurs from west to east. (Counter clockwise) Earth s rotation is the cause for day and night.

13 EXPLAIN Earth is a little chubby around the middle. Technically, Earth is an oblate spheroid. It is wider at the equator than at the poles. This is caused by the rotation of the Earth on its axis.

14 EXPLAIN - Other Movements Precession - Keeps the tilt of the Earth s axis, but changes the direction where the axis points (like a spinning top that is slowing down). Takes a very long time for these movements to happen. We can measure them, and we know they are happening, but we don t see the effects within a human lifetime.

15 EXPLAIN - Other Movements Nutation - Earth s tilt on it s axis changes slightly from 23.5 degrees to 23 degrees to 24 degrees. This occurs over an 18 year period. This is due to the Moon. This causes a slight change in the seasons.

16 EXPLAIN - Other Movements Barycenter - Like the center of gravity or the balancing point of the solar system. Takes a very long time for these movements to happen. We can measure them, and we know they are happening, but we don t see the effects within a human lifetime.

17 EXPLAIN - Kepler's First Law The focus (Sun) is slightly off center therefore causing an elliptical orbit. Where is the earth closest to the sun? Where would the sun s gravitational pull be the strongest on earth?

18 EXPLAIN - Kepler's Second Law When the orbiting body is closest to the focus, it moves fastest. The farther away it is, the slower it moves. BUT in a given amount of time, the body will cover the same amount of area regardless of it s location.

19 EXPLAIN - Kepler's Third Law The farther away the orbiting body is from the focus, the more distance it takes to complete it s orbital path.

20 EXPLORE/ELABORATE: KEPLER S LAW LAB

21 EVALUATE The length of a year is determined by the amount of time it takes A. the Moon to revolve around Earth. B. Earth to revolve around the Sun. C. Earth to rotate on its axis. D. the Sun to rotate on its axis.

22 EVALUATE A new planet is discovered orbiting a single star. The planet has one moon. According to Kepler s First Law, what do scientists know about the orbit of the planet around the star? A. The orbit is circular with the star at the center of the circle. B. The orbit is elliptical with the star at one focus of the ellipse. C. The planet takes 12 times longer to orbit the star than the moon takes to orbit the planet. D. The planet orbits the star in a direction opposite to the direction of the moon s orbit of the planet.

23 EVALUATE The planet below is orbiting the Sun. The two sweeps are on opposite sides of the Sun and are labeled t. Though the orbital distance covered in each sweep is different, the time interval for each sweep is the same. Areas A and B are bounded by the arcs of the planet s sweep in time, t, and the lines between the endpoints of the arc and the center of the Sun. What is the relationship between Area A and Area B? A. Area A is 50% larger than Area B. B. Area A is 50% smaller than Area B. C. Area A is the same size as Area B. D. Area A is twice as big as Area B.

24 EVALUATE Earth travels on an elliptical orbit around the Sun. When Earth is at the point labeled on the diagram, it moves most quickly in its orbit. Which best explains this more rapid motion of Earth? A. The amount of solar heat reaching Earth is greatest at this point. B. The Sun s gravitational pull on Earth is strongest at this point. C. Earth is closest to the Sun s magnetic field at this point. D. Earth is closest to the Sun s radioactivity at this point.

25 EEn Explain how the Earth s rotation and revolution about the Sun affect its shape and is related to seasons and tides. I Can Explain how the relative motions of the earth, sun, and moon cause ocean tides. Explain the reason that earth has four seasons based on the tilt of the Earth s axis of rotation and Earth s motion relative to the sun. Relate earth s initial formation to its present day spherical shape.