Transcript Sponge: Tell three reasons reflectors are better than refractors.

Sponge:
Tell three reasons
reflectors are
better than
refractors.
The Earth has a
circumference of
40,000 km and a
radius of 6500 km
(6378 km).
The volume of the
solid and liquid
27
3
parts is 10 cm .
(no gases or
magnetosphere)
Its mass is 6.0 x
27
10
g.
(6000 billion billion tons)
(Atmosphere and
magnetosphere make up
less than 0.1% of mass)
27
10 g
Density is 6 x
27
divided by 10 cm3.
Avg density =
3
6 g/cm
For comparison, water
3
has a density of 1 g/cm ,
3
crust rock is 2 to 4 g/cm .
Since the average is 6
3
g/cm , the Earth must be
much denser below the
crust.
The Earth has an
equatorial bulge
40 km larger than
the polar diameter
(because of rotation
speed).
This is 40 km
compared to a total
diameter of 13,000 km;
the Earth is smoother
and more spherical
than a billiard ball.
The Earth has six
main regions:
1) Magnetosphere zone of charged
particles trapped by the
Earth’s magnetic field.
2) Atmosphere - air
3) Crust - solid
continents and sea
floor
4) Hydrosphere oceans
5) Mantle - huge layer
of rocky material below
the crust and above the
core.
6) Core contains a liquid
outer layer and
a solid inner
layer.
Hydrosphere
3/4 of the Earth’s
surface is covered
by water to an
average depth
of 3,682 meters.
2 % of the water
on Earth is in
lakes and rivers,
98% in oceans.
Tides - the rising and
lowering of ocean
water levels due to
the gravitational pull
of the Moon.
There are two high and
two low tides each day.
The typical change in
level from low to high is
1 meter.
(In some places it can be
as high as 20 m.)
The gravitational influence of the
Moon causes a tidal bulge on the
side toward the Moon and the
side away from the Moon.
Rotation actually causes the tidal
bulges to be offset in the direction
of rotation.
Spring tides - higher tides
because the Sun’s gravity is
adding to the tidal bulge.
Neap tides - lower because the
Sun is pulling at a right angle.
Spring tides occur twice per
month when the Moon, Earth,
and Sun are lined up.
Neap tides occur twice per
month when the Moon has
moved to a position at a right
angle to the Earth-Sun line.
Tidal forces - refers to any
variation of gravity across a large
body like the Earth or Moon.
This variation of the Moon’s
gravitational pull which causes
the ocean tides is just one
example.