Transcript Lecture 16 - Empyrean Quest Publishers

NOTES: The Solar System:
Origin: the nebular theory fits most of the facts.
The nebular theory:
1. The Big Bang produced lumpy clouds--COBE satellite.
2. Recycled star stuff with heavier elements combined with H and He gas
from Big Bang, and gravity pulled it together.
There were two supernova in our region.
3. The gas cloud collapsed to a spinning disk and a globe in the center.
4. It heated as it collapsed, the center hotter than outer regions:
Helmholtz contraction or heating.
5. The sun's magnetic field slowed its rotation by dragging on
electrons.
6. There were swirls formed to predate satellite systems.
7. The inner regions were too hot to allow light gases to collect.
This left heavier elements and produced terrestrial planets.
8. The outer regions were cool enough to allow large amounts of H and He
to collect into the Jovian Planets.
9. Dust collected into planetesimals, planetesimals into protoplanets.
Gravity smoothed the larger objects to spheres.
10. All planets, the sun, and satellites rotated and revolved in the same direction
(prograde). Some planets (Venus, Uranus and Pluto) rotate retrograde
because of large collisions (Velikovsky).
Steps in how the solar nebula forms.
The Nebular Hypothesis
Conservation of Angular Momentum:
Contraction  increase in rotation,
shown in reverse above.
Hannes Alfven explained
why the sun seemed to rotate
slower than conservation of
angular momentum would
suggest
If you spin underwater
with your arms out,
it slows you down.
The magnetic field in the
solar nebula disk is like the
arms, the charged particles
in that disk are like the water.
The Solar Nebula heated as it collapsed,
the center hotter than outer regions:
Helmholtz contraction or heating.
Compressing a gas makes it hotter, as
particles move faster.
Gravitational potential
energy between
dust particles and gas
becomes kinetic energy
of motion or heat.
The inner regions were too hot to allow light
gases to collect.
This left heavier elements and produced
terrestrial planets.
Planetesimals (rocks) formed out of the dust by gravity.
Planetesimals
condensed into
planets, moons,
and asteroids.
Protoplanet model by Pawel Artymowicz of Sweden
Prograde vs Retrograde Rotation:
Only Venus, Uranus spin retrograde
--opposite to earth.
Velikovsky in 1950’s
suggested
Venus was hit
by something big,
flipping her rotation.
He was labeled a ‘crackpot’.
Bode's Law: Planet Dist. in AU = (3x2n-1 + 4)/10, n = 1, 2, 3, ...
Planet
Prediction Actual Distance
Mercury
0.4
0.39
Venus
0.7
0.72
Earth
1.0
1.00
Mars
1.6
1.52
Ceres
2.8
2.8 (Largest in asteroid belt)
Jupiter
5.2
5.20
Saturn
10.0
9.54
Uranus
19.6
19.18
Neptune
38.8
30.06
Pluto
77.2
39.44 (was Pluto an original?)
No reasonable explanation why this works.
Distances found by radar ranging--bouncing radio waves and
timing.
Radar Ranging: bounce radio waves
off planetary body.
Distance = speed of light x time
Mass:
Found using Newton's version of Kepler's 3rd Law a3/P2 = kM.
This gives mass of sun. Then, let M = the mass of a planet with
a moon in orbit about it. Planets without moons have masses
determined by orbiting spacecraft or deviations in trajectories
(paths) of passing objects.
Planetology:
Example--content of Atmospheres: depends on
1. Volcanism, and origin of planet.
2. Surface temperature--a measure of average speed of atoms
and molecules.
3. Surface gravity and escape velocity.