In Class:
Question to Ponder
The ``habitable zone'' on Earth (i.e, where life exists) extends from
high mountain terrain about 20,000 ft (6000m) above sea level to deep
ocean trenches a similar distance below sea level. Based on these
numbers, what fraction of the Earth's radius does this habitable zone
occupy (you can approximate the Earth's radius as 6000 km).
- a) 0.2 %
- b) 1 %
- c) 2 %
- d) 20 %
- e) 100 %
The Magnetosphere
- Last, outermost bit of the Earth's protective screen.
- Earth's interior acts like a magnet; creates field lines that
envelop the Earth.
- The magnetic field deflects incoming charged particles from
the solar wind.
- This is a good thing, since these charged particles have high
energy and can damage living tissue.
- The magnetic field guides these particles toward the polar regions,
where they occasionally interact with the upper atmosphere, producing
the "northern lights," or aurora borealis (aurora
australis in the southern hemisphere).
The Moon's Effect on the Earth: Tides
- As planetary moons go, our Moon is pretty big.
- At 1% of the Earth's mass, the Moon is the largest moon in the
Solar System, when measured as a fraction of its parent planet's mass.
(other moons are bigger, but they're found around much bigger planets).
- The gravitational tug of the Moon produces tides
on the Earth (see the special web page on
tides for more detail).
- Tides may have been essential for the establishment of life on Earth.
- Some theories for the development of life depend on the periodic
filling and emptying of tidal basis to transport nutrients and remove wastes.
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