Lecture Notes: 

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Lecture #26, April 22

• READ SNOW CHAPTER 13 PAGES 286-301
• LOOK OVER THOUGHT QUESTIONS #1,2,8,9,10.

• LIGHTNING BOLT HURLING ZEUS

Unlike Venus, the planet Jupiter has just the right name. Not only 
is it the largest of the planets, but it "hurls" the greatest thunderbolts 
between Io and its poles. 
The high rotational rate of Jupiter results from the conservation of 
angular momentum. Due to conservation of linear momentum, the rapid rate 
of rotation has produced an oblate shape to the planet with a equatorial 
diameter some 9000 km greater than its polar diameter. 
Posiden (Neptune) also could be associated with the planet as huge 
tides are raised in its atmosphere by Io. The volcanoes of Io are also 
signs of the activities of that god of the sea and earthquakes. 
Not only do those lightning bolts produce auroras in Jupiter's 
atmosphere, but they generate radio bursts, which sometime produce static 
on our TV sets. 

• MAGNETIC FIELDS OF PLANETS

Magnetic fields are produced whenever electrons flow in a circular 
current, such as in wires wrapped around an iron plug as in an 
electromagnet. Both charged particles and circular motion are thus 
necessary to produced magnetic fields. Venus has the same hot interior as 
the earth, but because it rotates so slowly, 225 days, it can not generate 
a magnetic field. On the other hand, rapidly rotating Jupiter produces the 
strongest field of all the planets. 

• RESONANCES AT SATURN


The great gap in the rings of Saturn between the A and B rings, 
known as Cassini's division, lies at a distance of 120,000. Material that 
would be in that gap would revolve with a period of 0.47 days around 
Saturan. The Saturnian moon, Mimas, which a huge impact crater on its 
surface, has a period of 0.94 days. The exact 1:2 resonance produces a gap 
similar to the Kirwood gaps in the asteroid belt.