Astronomy: A Search for Origins!!!

9. 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.

10. 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

11. 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

12. 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.

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

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 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.

20. 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

21. 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 3.4 billion year old stromatolite fossils 0.3 billion year old trilobyte URL

22. 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

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

24. 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. Lecture Notes: Lookback time

25. 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

26. “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.

27. “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.

28. “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.

29. 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 • Light travels “slowly”. The stale view of the universe permits Astronomers tolook backin time. Radio observationscan detect light originating from the warm, glowing universe shortly (300,000 years) after the Big Bang

30. 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

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

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

33. Human Biases • Location

34. Human Biases • Location

35. Human Biases • Location

36. 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 • 300K room temperature vs. 3K elsewhere.

37. Human Biases • Location

38. Human Biases • Wavelength

39. Human Biases • Wavelength • The universe looks quite different when we look outside the tiny slice of the spectrum accessible to the human eye.

40. Human Biases • Wavelength

41. Human Biases • Comprehending large numbers • It's easy to visualize 5, 10, or even 100 things. • What's the difference between a million, a billion, or a trillion (from a visualization standpoint) • How do we make large numbers conceptually meaningful?

42. Human Biases • Comprehending large numbers • It's easy to visualize 5, 10, or even 100 things. • What's the difference between a million, a billion, or a trillion (from a visualization standpoint) • How do we make large numbers conceptually meaningful? • The mass of the Sun is 2,000,000,000,000,000,000,000,000,000,000 kg • Using scientific notation makes the above number manageable, but not necessarily comprehensible. = 2 x 1030 kg

43. Human Biases • Scale models can put these numbers in a relative context.

44. Human Biases • Scale models can put these numbers in a relative context. NO!