Chapter 2 The Science of Life in the Universe

Transcription

1 Chapter 2 The Science of Life in the Universe The Big Idea This is a perspective Chapter How did we get to the point where we can address the question of extra-terrestrial life in a scientific way? And what does scientific way mean, anyway? Jump ahead 1

2 Ch The Copernican Revolution The Heliocentric All Star Team I. Nicholas Copernicus (~1540) revives the heliocentric idea Tycho Brahe (~1580) most precise naked-eye planetary positions accuracy ~1/60 of a degree! Johannes Kepler (~1610) detailed analysis of Tycho s data heliocentric model works best planet orbits are ellipses planet orbital speeds vary bigger orbits longer periods 3 Laws of Planetary Motion (see Figs ) 2

3 Ch The Copernican Revolution The Heliocentric All Star Team I. Nicholas Copernicus (~1540) revives the heliocentric idea Tycho Brahe (~1580) most precise naked-eye planetary positions accuracy ~1/60 of a degree! Johannes Kepler (~1610) detailed analysis of Tycho s data heliocentric model works best planet orbits are ellipses planet orbital speeds vary bigger orbits longer periods 3 Laws of Planetary Motion (see Figs ) 3

4 The Heliocentric All Star Team II. Galileo (early 1600 s) first telescopic observations favored heliocentric model (but couldn t prove Earth moves!) early understanding of physics of motion Isaac Newton (~1700) discovered physical principles behind Keplers results mathematically describes the physics of motion Newton s Three Laws of Motion (see Fig 2.12) 4

5 The Heliocentric All Star Team II. Galileo (early 1600 s) first telescopic observations favored heliocentric model (but couldn t prove Earth moves!) early understanding of physics of motion Isaac Newton (~1700) discovered physical principles behind Keplers results mathematically describes the physics of motion Newton s Three Laws of Motion (see Fig 2.12) 5

6 Kepler s Three Laws 1. Orbits are ellipses 2. Orbital speed changes during orbit 3. Orbital size and period are related 6

7 But What About Extraterrestrial Life? Greek atomists believed heavens composed of same element as Earth - and populated by life. Others ( Aristotelians ) believed Earth to be unique the special center of the Universe Copernican Revolution showed that Earth does not occupy a special place in the Universe Earth is just another place What happens here probably happens in lots of other places Made it easier to believe the life might exist elsewhere 7

8 So it seems intellectually reasonable to think about extra-terrestrial life But how do we approach the issue scientifically? 8

9 Ch The Nature of Modern Science definition: science = the view that the physical Universe is governed by a welldefined set of rules (i.e., is a rational place) = the endeavor to uncover those rules The rules that govern the physical Universe can be expressed mathematically (this is a great thing) 9

10 The Scientific Method An idealized view of how science proceeds This is the key part A scientific theory is testable A scientific theory is falsifiable A scientific theory can never be proven to be right! Fig

11 Distinguishing Science from Pseudo-Science There are several characteristics which define scientific thinking UFO-ology, creationism, belief in psychic powers, astrology, etc. all fail to achieve one or more of the hallmarks. They are not science Fig

12 So, our approach to Life in the Universe will be a scientific one. We will utilize only reliable & repeatable observations If we formulate any conclusions, explanations, or theories, they must be testable and falsifiable! 12

13 Science in Action Ch The Fact and Theory of Gravity Isaac Newton Newton first realized that an attractive force (gravity) could explain many different phenomena Falling apples, rocks, cows, Earth s orbit around Sun Moon s orbit around Earth, etc. Strength of force depends only only on masses & separation! Successfully predicted comet orbits, existence of Uranus, Fig

14 But what the heck is a force Action at a distance sounds a bit like magic. Newton s Universal Law of Gravitation really doesn t tell us what gravity is. And it doesn t actually work all the time! 14

15 Albert Einstein Suggests gravity results from curvature of space! mass distorts space orbits are straight lines in curved space! Fig 2.17 General Relativity reproduces all of Newton s results plus - it works in places where Newton s theory didn t 15

16 General Relativity has passed all tests so far But is it right? Do we understand gravity? Probably not! GR not consistent with quantum mechanics (the study of the subatomic world) There s probably a bigger theory out there, but we don t know what it is yet predicting & testing go on 16