1. 2 nd Law of Thermodynamics 1 st Law – conservation of energy 2 nd Law – no cyclic process which converts heat entirely into work is possible. Can’t build a perpetual motion machine Entropy is a measure of disorder (random motion of particles) In all natural processes, the entropy of the universe increases.

2. Order (opposite of entropy) Order Time

3. Formation of the Solar System Page 43-50

4. GWU Astronomy Bob Fest Saturday January 25 8-5 (9 first program) Tucker Student Center 20 extra points test grade

5. Basic Materials Earth, Moon, Terrestrial Planets, asteroids, meteoroids, comets Heavy elements – Oxygen, silicon, aluminum, iron, carbon, calcium – Very Little Hydrogen and Helium Sun, Stars interstellar clouds – Light elements – Hydrogen, helium – 99% of all atoms, 98% of all mass

6. Big Bang Not big and not a bang Extrapolated the expanding universe back, back, back in time 13.5 to 14.6 billion years ago An explosion that created all space, time, matter and energy Astronomy begins a few minutes after the “beginning”

7. Limits of Science My Opinion Science can not teach us what happened “in the beginning” or before the “beginning” I use the Genesis account – In the beginning, God created… – The universe is not a purposeless, random process You chose your faith

8. Heavy Elements Big Bang formed – Hydrogen, Helium, Lithium Heavier elements were formed in stars – Nuclear fusion – Hydrogen fused to form helium – Helium fused to form carbon – Carbon transformed into heavier elements nitrogen, oxygen, neon, silicon, iron

9. Star Material Ejection Stellar Winds – Routine explosions expel outer layer Planetary nebulae – More energetic outburst Supernovae – Giant explosion formed heavier elements

10. Cone Nebula Page 131

11. Newly formed stars in Orion Nebula

12. Other Observations All planets orbit in the same direction All planets orbit in a flat plane Almost all planets spin in the same direction Rocky planets near sun Gas giants far from sun

13. Solar Nebula The solar system formed from a fragment of a vast cloud of interstellar gas and dust Diameter of at least 100 AU 2-3 times the mass of the sun Collapsed due to – Winds from nearby stars – Explosion of another supernova – Pairs of clouds compressed each other – Radiated away enough energy to collapse Gravitational attraction collapsed further

14. Page 46

16. Protosun Slowly rotating cloud Deep inside the nebula, gravitational attraction caused the gas and dust to “fall” to the center Pressure, density and temperature increased Protosun Atoms collided with each other producing heat Matter near center rotated faster

17. Protoplanetary disks Gravity, collisions and rotation produced irregular cloud fragments These fragments slowly came together Formed larger objects planetesimals Planetesimals collided and stuck together forming protoplanets Process of accretion continued for 100 million years.

18. Computer Simulation (P47)

20. Outer Planets Core accretion model Beginning with a “seed” rocky core Attracted rock, gas, ices Eventually the giant mass attracted hydrogen and helium Gas giants formed Hydrogen and helium were pushed out of the inner solar system by solar winds.

21. Meanwhile back at the Ranch Sun continued to heat up due to collisions of atoms Reached 10 7 K Ignited hydrogen fusion Star process – produces energy from fusion of hydrogen into helium

22. Early solar system Very active place Lots of debris Lots of collisions- craters on moons

24. We see similar things in Orion Nebula

25. What the model explains Number and make up of terrestrial planets Make up of Gas giants Flatness of the Ecliptic Rotation all in one direction Craters on Moon and moons