Preface 1

1 Introduction

1.1 The cosmological standard model . . . . . . . . . . . . . . . . . . . . 4

2 How does Science work? 13

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.2 Scientific Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.3 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.3.1 Colour dependent gravity . . . . . . . . . . . . . . . . . . . . 17

2.3.2 The Perihelion Shift in the Orbit of Mercury . . . . . . . . . . 19

2.4 Changing Theory in Physics . . . . . . . . . . . . . . . . . . . . . . . 20

2.5 Cosmological Simulations . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.2 What reaches us . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.2.1 Different forms of light - electromagnetic radiation . . . . . . 28

3.2.2 Non-standard messengers - neutrinos and gravitational waves 31

3.3 How Observations are Made . . . . . . . . . . . . . . . . . . . . . . . 34

3.3.1 Optical Telescopes . . . . . . . . . . . . . . . . . . . . . . . . 35

3.3.2 Radio Telescopes . . . . . . . 1 . . . . . . . . . . . . . . . . . . 38

3.3.3 Microwave Telescopes . . . . . . . . . . . . . . . . . . . . . . . 40

3.3.4 Examples for non-standard messenger observatories . . . . . . 43

3.4 Future experiments and telescopes . . . . . . . . . . . . . . . . . . . . 47

3.5 Closing Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4 What can we actually observe and measure? 51

4.1 Things we can observe directly . . . . . . . . . . . . . . . . . . . . . . 51

4.2 Distance units in cosmology . . . . . . . . . . . . . . . . . . . . . . . 55

4.3 How to measure distances in cosmology . . . . . . . . . . . . . . . . . 56

4.5 A very large map: the distribution of galaxies . . . . . . . . . . . . . 63

4.6 An even larger map: the Cosmic Microwave Background . . . . . . . 66

5 What is the universe made of? 69

5.1 Familiar types of matter, what is normal stuff made off? . . . . . . . 69

5.1.1 Matter on the smallest scales - up to atoms . . . . . . . . . . 69

5.1.2 Larger scales - particles interacting . . . . . . . . . . . . . . . 71

5.1.3 Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

5.2 Where does normal matter come from . . . . . . . . . . . . . . . . . 76

5.3 Exotic Stuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

5.3.1 Dark Matter - Cold and Hot . . . . . . . . . . . . . . . . . . . 79

5.3.2 Dark matter candidates - WIMPS, MACHOS, and Black Holes 82

5.4 Weird stuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

5.4.1 The cosmological constant - _ . . . . . . . . . . . . . . . . . . 83

5.4.2 Quintessence . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

6 What underlying Forces shape the Universe? 87

6.1 The four forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

6.2 What are forces and fields . . . . . . . . . . . . . . . . . . . . . . . . 88

6.3 Forces in Newtonian mechanics . . . 1 . . . . . . . . . . . . . . . . . . 88

6.4 Electromagnetism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

6.5 The other forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

6.6 Gravity . .