Contact Information

1. Contact Information • Mike Skrutskie – mfs4n - 924-4328 • Room 262 – Astronomy Building • Office Hours: • Monday 1:30 – 2:30 • Thursday 10:30 – 12:00 Room 262 Astronomy (my office) • if those don't work contact me for arrangements • Course TA • Kim Sokal - krs9tb • Room 267 Astronomy Building • By appointment

2. How Do You Make Sense of it All?

3. Astronomy: A Search for Organization? Stars.... Galaxies....

4. Astronomy: A Search for Organization?

5. Our Galaxy (the Milky Way) in Perspective: How do we fit in? • Galaxies, collections of billions of stars assembled and bound by gravity, are a primary unit of Universal structure. • Any random deep view of the night sky shows a universe peppered with galaxies – each containing hundreds of billions of stars.

6. Our Galaxy (the Milky Way) in Perspective: How do we fit in? • Imagine we are able to travel to a point billions of light years away and look back toward our galaxy... Us?

7. Our Galaxy (the Milky Way) in Perspective: How do we fit in? Our sun (a star) resides out toward the edge of a thin and flat collection of 100 billion stars – the Milky Way Galaxy A distant galaxy similar to our Milky Way The Stars Near Our Sun Associated WWW Link

8. Our Galaxy (the Milky Way) in Perspective: How do we fit in? The Stars Near Our Sun Associated WWW Link

9. Our Galaxy (the Milky Way) in Perspective: How do we fit in? • The Sun is embedded in the Milky Way (far from the center). • We have a myopic perspective. • The Milky Way is thin and flat, yet we see a lumpy diffuse band across the sky because of our proximity.

10. Our Galaxy (the Milky Way) in Perspective: How do we fit in? • The Sun is embedded in the Milky Way (far from the center). • We have a myopic perspective. • The Milky Way is thin and flat, yet we see a lumpy diffuse band across the sky because of our proximity.

11. Our Galaxy (the Milky Way) in Perspective: How do we fit in? • The Sun is embedded in the Milky Way (far from the center). • We have a myopic perspective. • The Milky Way is thin and flat, yet we see a lumpy diffuse band across the sky because of our proximity. Aitoff Projection

12. Our Galaxy (the Milky Way) in Perspective: How do we fit in? • Infrared light penetrates dust better than visible light. • An infrared view of the Milky Way reveals the real Galaxy.

13. Astronomy: A Search for Structure? • Hierarchical structure in the Universe leads to an extended mailing address..... Earth The Solar System (in capital letters) The Milky Way Galaxy The Local Group The Local Supercluster The Universe • Implicit in understanding this structure is knowing how far away things actually are.... not an easy task!

14. Understanding Structure: Divining Depth

15. Understanding Structure: Divining Depth

16. Understanding Structure: Divining Depth Still, we are focusing on phenomenology....

17. Astronomy: A Search for Origins!!! • Where did all the structure and organization come from? • How did it emerge over time? • What were the starting conditions? • What physical processes were important? • We wish to explain, not just observe.

18. Astronomy: A Search for Origins!!! • Where did all the structure and organization come from? • How did it emerge over time? • What physics/physical processes were important? Hydrogen + Helium + Gravity ⇨ Stars, Galaxies, and Humans given about 14 billion years.

19. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • - a numbernow known to better than 1 percent! • The early Universe containedonlyuniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” for previous generations of stars. • At the same time system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Lecture outline: A Brief Brief History of the Universe

20. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravitybegins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” for previous generations of stars. • At the same time system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Lecture outline: A Brief Brief History of the Universe

21. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” for previous generations of stars. • At the same time system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago.

22. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” for previous generations of stars. • At the same time system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Lecture outline: A Brief Brief History of the Universe

23. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” for previous generations of stars. • At the same time system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Lecture outline: A Brief Brief History of the Universe

24. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” of previous generations of stars. • At the same time a system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Lecture outline: A Brief Brief History of the Universe

25. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” of previous generations of stars. • At the same time a system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Stars die Stars form Lecture outline: A Brief Brief History of the Universe

26. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” of previous generations of stars. • At the same time a system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Lecture outline: A Brief Brief History of the Universe

28. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” for previous generations of stars. • At the same time system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Lecture outline: A Brief Brief History of the Universe

29. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” for previous generations of stars. • At the same time system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago. Lecture outline: A Brief Brief History of the Universe

30. A Five-Minute History of the Universe • The “Big Bang” brings matter, space and time into existence. • It happened 13.7 billion years ago. • a number now known to better than 1 percent! • The early Universe contained only uniformly distributed Hydrogen and Helium. • Almost immediately gravity begins to form stars and galaxies. • Stars “process” Hydrogen and Helium into heavier elements like Iron, Calcium, and Oxygen. • After 9 billion years of cosmic recycling (4.6 billion years ago) our Sun forms from the “ashes” for previous generations of stars. • At the same time system of planets form from debris left in orbit around the Sun. • Life originates quickly on Earth. • but only becomes “complex” ½ billion years ago.

31. A Single-Year Perspective • If this history could be compressed into a single year: • The Universe starts on January 1... • The Solar System forms in early-September

32. A Single-Year Perspective • If this history could be compressed into a single year: • The Universe starts on January 1... • The Solar System forms in early-September • Life on Earth originates in mid-September • - Life becomes complex in early-December 3.4 billion year old stromatolite fossils 0.3 billion year old trilobyte URL

33. A Single-Year Perspective • If this history could be compressed into a single year: • The Universe starts on January 1... • The Solar System forms in early-September • Life originates in mid-September • - Life becomes complex in early-December • Dinosaurs roamed the Earth for two weeks between December 10 and December 25 • Humanity (intelligence?) arose at 10 p.m. on December 31 • Recorded history began around 11:59:45 on December 31

34. Overcoming Human Biases • Location, Wavelength, and Time to name a few Lecture Notes: Human Biases in Astronomy

35. Human Biases • Time • A human lifetime is a blink of the eye relative to the timescale of cosmic events. • - Going back to that cosmic year, a human lifetime is about 2 one-hundredths of a second. • Stars and galaxies change incredibly slowly by comparison. • Astronomers must reconstruct the workings of the Universe from this “snapshot” view. Lecture Notes: Lookback time

36. Lecture Notes: Lookback time

37. Human Biases • Time • A human lifetime is a blink of the eye relative to the timescale of cosmic events. • - Going back to that cosmic year, a human lifetime is about 2 one-hundredths of a second. • Stars and galaxies change incredibly slowly by comparison. • Astronomers must reconstruct the workings of the Universe from this “snapshot” view. • The Astronomer's task is similar to asking an alien anthropologist to reconstruct the intricacies of human relationships and politics from a snapshot of the events happening on Earth at one instant. Lecture Notes: Lookback time

38. Human Biases • Time • A human lifetime is a blink of the eye relative to the timescale of cosmic events. • Astronomers must reconstruct the workings of the Universe from this “snapshot” view. • This task is similar to reconstructing the intricacies of human relationships and politics from a snapshot of the events happening on Earth at one instant. • Astronomers have two powerful tools to address this shortcoming • Light travels “slowly”. A stale view of the universe permits Astronomers tolook backin time. Lecture Notes: Lookback time

39. “Lookback” Time • Light takes time to get from one place to another. • Light travels at a speed of 300,000 km/s • The travel time is instantaneous for most everyday experience where distances are small. • Travel time becomes important for more distant objects • Light takes just over a second to get to the Moon (400,000 kilometers away). • In a year light traverses a distance of a light-year.

40. “Lookback” Time • We get a “stale” view of the Universe, seeing more distant object as they were in the more distant past. • We see the Sun as it was 8.3 minutes ago because the light took 8.3 minutes to traverse the distance from the Sun to the Earth (150 million kilometers). • For extremely distant objects, billions of light-years, the light takes billions of years to get here, bringing a view that is billions of years out of date.

41. “Lookback” Time • We see the Sun as it was 8.3 minutes ago because the light took 8.3 minutes to traverse the distance from the Sun to the Earth (150 million kilometers). • For extremely distant objects, billions of light years, the light takes billions of years to get here, bringing a view that is billions of years out of date. • We see the distant universe as it was in the distant past.

42. Human Biases • Time • A human lifetime is a blink of the eye relative to the timescale of cosmic events. • Astronomers must reconstruct the workings of the Universe from this “snapshot” view. • This task is similar to reconstructing the intricacies of human relationships and politics from a snapshot of the events happening on Earth at one instant. • Astronomers have two powerful tools to address this shortcoming • Light travels “slowly”. A stale view of the universe permits Astronomers to look back in time. • Computer simulation can permit scientist to watch events play out over millions or billions of years. • Insert the laws of physics and turn the crank... Lecture Notes: Lookback time

43. Simulation Real Some computer animations: Collision between Galaxies Formation of Structure in the Universe

44. Simulation Real Some computer animations: Collision between Galaxies Formation of Structure in the Universe Tour the Millenium Simulation

45. Human Biases • Location

46. Human Biases • Location

47. Human Biases • Location

48. Human Biases • Location • High density of matter compared with intergalactic space. • 1019 atoms per cubic centimeter in air. • 1 atom per cubic “stadium” in intergalactic space. • High temperature compared with intergalactic space • 300 Kelvins room temperature vs. 3 Kelvins elsewhere. • Dominance by elements other than hydrogen and helium.

49. Human Biases • Location

50. Human Biases • Wavelength