1. Exploration of the Universe Lives of the Stars

2. Two Profound Ideas The Sun is a Star We Are Made of Starstuff

3. Large Numbers 10 x 10 x 10 x 10 = 10 4 10 x 10 x … (n times) = 10 n To multiply, add exponents – 10,000 x 100,000 = 1,000,000,000 – 10 4 x 10 5 = 10 4+5 = 10 9

4. More About Large Numbers 1,000,000,000/10,000 = 100,000 10 9 /10 4 = 10 5 = 10 9-4 To divide, subtract exponents 1000/100 = 10 3 /10 2 = 10 3-2 = 10 1 = 10 Anything to the first power equals itself

5. A “Paradox” of Scientific Notation Not really a paradox, but hard for many people to accept 100/100 = 10 2 /10 2 = 10 2-2 = 10 0 = 1 Anything to the zero power equals 1

6. Negative Exponents 1000/100,000 = 10 3 /10 5 = 10 3-5 = 10 -2 = 1/100 =.01 10 n x 10 -n = 10 n-n = 10 0 = 1 10 -n = 1/10 n

7. Does Anybody Need Really Big Numbers? 10 100 = “googol” 10 10 100 = 10 googol = googolplex Statistical Physics: energy distribution of air molecules in a room – Need to know total possible energy states – Roughly 10 number of molecules = 10 10 26 – Not a googolplex, but still pretty huge

8. Infinity The symbol ∞ for infinity is not a number - you can’t calculate with it. The mathematician Georg Cantor studied transfinite numbers, denoted by א (Hebrew letter Aleph) – א 0 : integers (counting numbers) – א 1 : all numbers, or points on a line – א 2 : all mathematical functions

9. Forces in Nature Long Range – Gravity – Electromagnetism Short Range - Only Within Atoms – Weak Nuclear – Strong Nuclear Other???

10. Atoms Democritus 400 B.C. Lucretius 1st c. B.C. Medieval: new elements Definition of Element Ratios in Chemical Reactions Crystallography

11. Atoms Nucleus: Almost all Mass in Atom – Protons: Determines Element Identity – Neutrons – Protons repel (electromagnetism) but strong nuclear force is stronger, holds it together – Too many protons: unstable (radioactive) Electrons – The part that engages in chemical reactions

12. Why Alchemy Didn’t Work Atomic energies are measured in units called electron volts (ev - very tiny) Energy binding electrons to an atom are a few ev Energies binding particles in the nucleus are millions of ev Trying to alter elements by chemical means is like trying to crack a safe with a feather

13. The Heavens Are Not Changeless The Stars Move – Most of our constellations would have been unrecognizable to Neanderthal Man The Solar System Moves – Very few of our nearby stars would have been visible to the first humans Stars are Born, Live and Die – Many of our brightest stars did not exist in the days of the dinosaurs