1 Introduction Lecture 1

2 What is Science? l Science is a way of viewing the world based on the guiding principles: l Nature is lawful l Some of this lawful behavior is universal l The goal of science is to uncover the laws of Nature and use them to satisfy our species profound need to understand what we see around us. l Science also provides the basis of technology

3 Cosmological Principle l There is nothing special about our place in the universe l If this principle is true, then what we learn from studying our neighborhood of the universe will apply to the universe as a whole. l The principle is also known as the l Copernican Principle

4 Scientific Method l Based on testing and experimentation l Make a model (hypothesis) l Test the model Observations Experiments l Modify the model (if necessary) l Retest Improved techniques: better observations Better experiments l Based on evidence, not faith. l Discard false ideas, however pleasing they may be

5 Distances

6 Distance Units l Meters (m) and Kilometers (km) l Good for everyday distances l Astronomical Unit (AU) l Average distance between the Sun and Earth l 150 million kilometer l Lightyear (LY) l Distance light travels in 1 year l Light travels at 3 x 10 8 m/s in a vacuum About 7 times around the Earth in a second l So in a year, how far does light travel?

7 Really Big Numbers l Really big numbers are hard to understand… l Examples: 10,000,000,000, 10,000,000,000,000,000? l We will often use powers of 10 for large 1,000,000 = 10x10x10x10x10x10 = 10 6 l Each factor of 10 is called one order of magnitude

8 Really Small Numbers l Really small numbers are hard to understand also…! l Examples: , l Easier to use negative powers of 10 A million billionth is

9 Lightyear l There are about 3 x 10 7 seconds in a year l 60 s/min x 60 min/hr x 24 hr/day x 365 days/year ~ 3.15 x 10 7 s/yr l Light travels at 3 x 10 8 m/s (300 million km/s) l So, 3 x 10 8 m/s x 3 x 10 7 s= 9 x m = 9 x km

10 Whoever can no longer wonder, no longer marvel, is as good as dead… Albert Einstein

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13 Jupiter and Io

14 The Eagle Nebula

15 The Red Giant

16 Andromeda

17 M87 Distance:50 Mly Length of jets:5000 ly Mass of Black hole:3 billion Msun

18 Summary l Astronomy is a science l During this semester you will learn about a wide range of objects such as l Planets, the Sun, Neutron Stars, Super-giant Stars, Supernovas, Black holes, Galaxies etc. l This class should be one of the most interesting courses you take at FSU l See you next time!