Earth’s Role as a Body in Space

1. Earth’s Role as a Body in Space

2. Lesson 1 Earth’s Position and Movement Through Space (You Are Here )

3. Earth’s Position in Space What is Earth’s position within the hierarchy of the universe?

4. A. Earth’s Position in the Universe Earth’s Position in the Universe… • Earth  • Solar System (3rd planet from Sun)  • Milky Way Galaxy (the Orion Arm)  • Local Group (about 40 galaxies) • Supercluster (Virgo) • Universe! http://www.atlasoftheuniverse.com/ https://www.youtube.com/watch?v=_IVqMXPFYwI Pure Education Detailed Observation of the Universe

5. Earth’s Motion through Space How is Earth’s motion related to the origin of the galaxy and its solar system?

6. The Origin of Our Expanding Universe 1. The Big Bang Theory • universe began as a point & has been expanding ever since Notice how the galaxies in each successive picture are moving apart from the singularity? en.wikipedia.org

7. The Origin of the Milky Way 2. Astronomers hypothesize that the galaxy began as… A rotating, spherical cloud in space … a. Our solar system continues to orbit the center of the Milky Way because… it developed in the plane of the disk that orbited the central nuclear bulge of stars http://www.google.com/imgres?imgurl=http://casswww.ucsd.edu/archive/public/tutorial/images/mw.jpg&imgrefurl=http://casswww.ucsd.edu/archive/public/tutorial/MW.html&usg=__

8. b. A Diagram – Milky Way Galaxy Formation • http://lcogt.net/education/article/milky-way-galaxy • http://astronomy.nju.edu.cn/~lixd/GA/AT4/AT423/HTML/AT42304.htm

9. The Origin of the Solar System 3. Our solar system began when… …a rotating, interstellar cloud of gases (nebula) collapsed (due to gravity) & formed a sun & orbiting planets a. Earth orbits the Sun because … it was located outside the center of the spinning nebula

10. A Diagram - Origin of the Solar System (Draw this!) • http://csep10.phys.utk.edu/astr161/lect/solarsys/nebular.html Rotating cloud flattens as it contracts Early stages of rotating cloud of gas & dust Sun forms in center & planets form within flattened cloud. Radiation from the Sun drives away the “atmosphere” of hydrogen gas from the inner planets.

11. Lesson 2 Kepler’s Laws and Earth’s Orbit

12. Kepler’s Laws (Introduction)… Johannes Kepler, working with data painstakingly collected by Tycho Brahe (from 1576-1601) without the aid of a telescope, developed three laws which described the motion of the planets across the sky. http://www.nmspacemuseum.org/halloffame/images.php?image_id=131 Unless otherwise noted, the info on the slides on Kepler’s laws was taken from the following website: http://hyperphysics.phy-astr.gsu.edu/hbase/kepler.html

13. 1. Kepler’s First Law… The Law of Orbits: All planets move in elliptical orbits, with the sun at 1 focus. a. An ellipse is … oval shape centered on 2 points instead of 1 point. b. The orbital period of a planet is … how long it takes for it to travel a complete orbit around the Sun. c. We call this a year!

14. 2. Kepler’s Second Law… The Law of Areas: A line that connects a planet to the Sun sweeps out equal (=) areas in equal (=) times. • Earth sweeps out a longer path when it is closer to the Sun. • Earth moves fastest when it is closest to the Sun. http://phet.colorado.edu/en/simulation/my-solar-system http://www.mathacademy.com/pr/prime/articles/kepler/index.asp

15. 3. Kepler’s Third Law… The Law of Periods: The square of the orbital period of any planet is proportional to the cube of the semi major axis of its orbit. a. P² = a³(P = orbital period = unit of time in Earth yrs, a = length of the semi major axis) • If you know the distance of a planet to the Sun, you would be able to figure out its… orbital period. • Basically… The closer a planet is to the Sun, the shorter its orbital period is.

16. Kepler’s Third Law • Another way of thinking about this is that …The closer a planet’s orbit is to the Sun, the shorter its year will be. (Write that in the margin!) • For Examples: Appendix J on p. 921… • Mercury’s year is 88 (Earth) days • Venus’ year is 224 (Earth) days • Earth’s year is 365 (Earth) days • Mars’ year is 686 (Earth) days • Neptune’s year is 60,189 (Earth) days!!

17. Practice! Orbit Eccentricity • The eccentricity of an ellipse can be defined as the ratio of the distance between the foci to the major axis of the ellipse. • The more eccentric an orbit, the more of an oval it is. • The eccentricity is zero for a circle. • Of the planetary orbits, only Pluto has a large eccentricity. http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=175

18. Mini-Lesson 2: Barycenter The True Center of the Solar System!

19. Mini Lesson 2: Barycenter and Earth’s Orbit… Barycenter is …the center of mass between a planet and the Sun. 1. The law of universal gravitation states that… • every pair of bodies in the universe attracts each other with a force related to… • …mass (the more mass they have, the stronger the pull) AND • …distance (the farther apart they are, the weaker the pull)

20. Barycenter, Universal Gravitation, and the Wobbling Sun • The Sun wobbles around in its orbit because… • … the 8 planets are pulling on it as they orbit it!

21. Barycenter and Earth’s Orbit… 2. A planet, such as Earth, actually orbits… its barycenter with the Sun 3. The Sun orbits … the barycenter of the solar system. (It is NOT stationary in the sky as planets orbit it.) 4. Draw this! See next slide. http://www.barewalls.com/pv-605547_Barycenter-Diagram.html

22. Lesson 3 Earth’s Rotation Day and Night Earth’s Slightly Squashed Shape

23. Earth’s Rotation Causes Day and Night 1. Earth’s axis is… • … the imaginary line that goes through the N & S poles. 2. Day and night are caused by… • … the rotation of Earth on its axis - spinning towards & away from the Sun. (23.9345 hrs)

24. 3. When the Sun “rises” … • … we are actually spinning TOWARDS it • Sun “rise” on Myrtle Beach (looking towards the east over the Atlantic Ocean)

25. 4. When the Sun “sets” … • … we are actually spinning AWAY FROM it • … sun “set” over Ft. Lauderdale, FL (looking towards the west while on the Atlantic Ocean)

26. Think About It… Why are there 24 hours in a day? Earth spins… 15 degrees each hour There are 360 degrees in a circle (the circumference of Earth). 360 divided by 15 is 24 so there are 24 hours in a day! http://huntingtonastro.wikispaces.com/file/view/earth-rotation.png/199559520/earth-rotation.png

27. Still Thinking About It… The exact amount of time it takes Earth to spin one time on its axis is… • 23.9345 hours • If an Earth day was 5832.5 hours long (like that of Venus!) then… • It would take 243 days for Earth to spin one time on its axis! • Our day and night would be much longer! (And it would get really hot and really cold!)

28. 1. What motion causes Earth to take the shape of an oblate spheroid? Earth’s rotation 2. What force causes the Earth’s mass to move outward from its center at the equator as Earth rotates? centrifugal force Earth’s Rotation Causes Its Slightly-squished Shape…

29. Earth’s Rotation Causes Its Slightly-squished Shape… 3. There is a slight bulging at the equator and a slight squishing at the poles. 4. This causes the circumference at the equator to be slightly larger than that of the poles.

30. Earth’s Rotation and Its Shape… 5. Draw this  Notice the equatorial diameter is 42 km more than the polar diameter! Simulation: http://www.cleonis.nl/physics/phys256/equatorial_bulge.php

31. Lesson 4 The Seasons

32. Earth’s Orbit and Seasons… 1. The ecliptic is… • …the plane on which Earth orbits around the Sun http://en.wikipedia.org/wiki/Ecliptic

33. Earth’s Orbit and Seasons… 2. The tilt of Earth’s axis relative to the ecliptic is 23.5 degrees. http://republicanredefined.com/2010/03/02/chile-quake-shifted-earths-axis-and-made-days-shorter/

34. http://www.exploratorium.edu/ancientobs/chaco/HTML/TG-shadows.htmlhttp://www.exploratorium.edu/ancientobs/chaco/HTML/TG-shadows.html 3. Draw The Seasons!

35. Earth’s Orbit and the Seasons! 4a. What causes summer in the northern and southern hemispheres? when the hemisphere is tilted toward the Sun during Earth’s orbit

36. Earth’s Orbit and the Seasons! Fall occurs when a hemisphere is starting to tilt away from the Sun. Fall occurs when a hemisphere is starting to tilt away from the Sun.

37. Earth’s Orbit and Seasons… 5 . The seasons in the northern and southern hemispheres are opposite each other because… • When 1 hemisphere is tilted towards the Sun, the other is tilted away from it

38. http://www.onlytoptens.com/wp-content/uploads/2011/08/top-10-documentaries-march-of-the-penguins.jpghttp://www.onlytoptens.com/wp-content/uploads/2011/08/top-10-documentaries-march-of-the-penguins.jpg Seasons - Perihelion 6. Earth is closest to the Sun in January a. Our winter! b. This is called perihelion http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=2517

39. Seasons - Aphelion • And farthest from the Sun in July - • our summer! • This is called aphelion But in Antarctic it is winter (which makes it tough on the penguins!)

40. Lesson 5 Changes in The Seasons – Precession and Nutation

41. Precession Precession is… • the wobble in Earth’s rotational axis. 1. One full cycle of precession takes… • 26,000 years! 2. The force that causes precession is… • the sideways pull of the Moon & Sun on the Earth’s bulging equator. https://www.youtube.com/watch?v=dFzhjnjXc2o (Weebles wobble…)

42. The Moon’s orbit is tilted 5° which over time pulls on Earth… http://earthsky.org/astronomy-essentials/what-is-the-ecliptic

43. Precession… 3. Our current north star is… • Polaris • In about 12,000 years, our new north star will be… • Vega http://www.wwu.edu/skywise/a101_precession.html

44. Precession and Our Seasons… 4. Draw this! Aphelion Winter July Perihelion Summer January In 14,000 yrs Aphelion Summer July Perihelion Winter January Present http://earth.usc.edu/classes/geol150/stott/variability/orbitalchanges.html

45. A New North Star and Our Seasons… 5a. Winters in the N. hemisphere will be… • in June, July, and August • It will be colder here because Earth will be farthest from the Sun. 5b. Summers in the N. hemisphere will be… • in December, January, and February • It will be warmer here because Earth will be closest to the Sun.

46. http://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_99/bilskemp/natural_variability.htmlhttp://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_99/bilskemp/natural_variability.html Nutation… Nutation is… … a change in the angle of tilt of Earth’s axis 1. Present tilt of Earth’s axis is 23.5°. 2. The tilt can vary from 22.1° to 24.5 °.

47. http://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_99/bilskemp/natural_variability.htmlhttp://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_99/bilskemp/natural_variability.html Nutation… 3a. If the angle of tilt decreased to 22.1… there would be less of a temperature differenceb/tw seasons. 3b. If the angle of the tilt of Earth’s axis increased to 24.5… there would be more of a temperature differenceb/tw seasons.

48. Lesson 6 Tides

49. Tides… Tides are caused by… • the gravitational attraction among Earth, the Moon, and the Sun. 1. Tides are… the periodic rise and fall of sea level. a. High tide… • highest level to which the water rises b. Low tide… • lowest level of the water

50. The Cause of Tides… 2. What forces & heavenly bodies cause the tides? • gravitational pull of Moon on oceans facing it causes high tide • “centrifugal swish” oceans facing away from Moon experience less of a pull (high tide) • The sides of Earth NOT directly facing toward or away from the Moon experience low tide.