Introduction and The Nature of Science

1. Introduction and The Nature of Science

2. The Nature of Science Science: observation of the world and the constant testing of theories against nature, with the requirement that everything that is to be called science must be testable Practical, pragmatic, based on evidence Healthy skepticism

3. Rational approach to questions Dull slog through failures to reach a conclusion Answers lead to more questions What is a fact, law, hypothesis, theory? Can only address question that deal with the natural world

4. Astronomy is the oldest science

5. Ionia – the birthplace of science

6. What science is not Pseudoscience e.g. astrology

7. Limitations of Science • Science cannot address supernatural phenomena • hypotheses must be testable and falsifiable and experimental results must be repeatable

8. Theories in Science • Broad in scope • Supported by a large body of evidence • Explain • Incorporates confirmed observations, laws, and successfully verified hypotheses

9. e.g. Big Bang Theory

10. Law – description of how a natural phenomenon will occur • Fact – natural phenomenon repeatedly confirmed by observation, e.g. Venus takes 225 days to go around the sun

11. The Culture of Science • Social activity • Cooperation and competition

12. Science, Technology, and Society Technology applies scientific knowledge for some specific purpose

13. Astronomy The study of the universe “We are made of star stuff” Carl Sagan

14. The Universe The totality of all space, time, matter, and energy “The size and age of the Cosmos are beyond ordinary human understanding. Lost somewhere between immensity and eternity is our tiny planetary home. In a cosmic perspective, most human concerns seem insignificant, even petty.” Carl Sagan

15. "Why is the night sky dark?“

16. Olbers' Paradox: "Why is the night sky dark?“

17. The reason that this question is so important is because it can tell us about the distribution of stars and galaxies in the universe.

18. Consider the possibility that the universe is infinite and that it is filled with luminous objects (stars, and the galaxies that contain them). If this is true, then every sight line from the Earth will eventually intersect a bright object. This means that if the universe is infinite and contains an infinite number of bright objects, the night sky will be bright! Since the night sky is dark, this tells us that one of our assumptions about the universe is incorrect.

19. We know that the night sky is dark, so that it means that sight lines from the Earth do not all end on sources of light. This could be due to several different possibilities:

20. The universe is finite, that is, it ends at some point.

21. The stars run out at large distances.

22. There hasn't been enough time for the light to reach us from the most distant stars.

23. We will find out that we can actually estimate the age of our universe. Because the universe is not very old, the answer is thought to be No. 3 listed above. Since light takes time to reach us, we can see only those objects that are near enough to us that their light has reached us. • The Wikipedia Page on Olbers' Paradox

24. Introduction to Astronomy

25. Universe Totality of all space , time , matter, and energy

26. Earth • 15,000 km diameter

27. Sun • 1,500,000 km diameter

28. 1 light year • a unit of length • distance that light travels in a vacuum in one year • = 9.5 x 1012 or (9,500,000,000,000 km) or (9.5 trillion)

29. Scientific Notation example: 567,000. 5.67 x 105coefficientbaseexponent 1. The coefficient must be greater than or equal to 1 and less than 10.2. Thebase must be 10.3. The exponent must show the number of decimal places that the decimal needs to be moved to change the number to standard notation.  A negative exponent means that the decimal is moved to the left when changing to standard notation.

30. M 81 (a galaxy) • 100,000 light year diameter

31. A galaxy cluster • 1,000,000 light years diameter

32. Parsec • 1 parsec = 3.26 light years = 206264.8 AU = 3.086 x 1013 km.

33. Constellations • e.g. Ursa major

37. The Celestial Sphere

38. Important terms • Celestial poles – points where the Earth’s axis intersects the celestial sphere • Zenith - direction pointing directly "above" a particular location • Polaris – North star or pole star, very close to the north celestial pole • Horizon - apparent line that separates earth from sky

40. Earth’s Orbital Motion • We measure time by the Sun • From one noon to the next is a 24-hour solar day is a consequence of Earth’s rotation

41. The cause for the seasons?

42. The cause for the seasons • The most misunderstood fact in astronomy! • Has nothing to do with the distance of the Earth from the Sun • Is due to the tilt of the Earth’s axis of rotation

43. Seasonal changes

45. Earth’s orbit • Motion of the Earth around the Sun, at an average distance of about 150 million kilometers, every 365.25 mean solar days

46. Moon Phases • http://antwrp.gsfc.nasa.gov/apod/ap040829.html

47. Moon Phases

48. Eclipses • when one celestial object moves into the shadow of another e.g. when the Sun and Moon line up precisely when seen from Earth

49. Solar Eclipse

50. Solar Eclipse