Posted by Art on October 23, 1997 at 08:21:09:
In Reply to: I'm confused! posted by Lana Cho on October 20, 1997 at 16:20:54:
: In our sidereal time handout, it says that if we're on the
: North Pole, the celestial equator is on the horizon all
: around us. I'm confused because, isn't the celestial
: equator an extension of the earth's equator which is located
: on the middle of the earth, dividing the earth into a
: southern and northern hemisphere??? And if this is true,
: then wouldn't that mean that if we're on the North Pole, the
: celestial equator would be BELOW us, out of our line of
: vision?? Also, what is the exact definition of the horizon?
: And lastly, how do I answer question number 17 in chapter 3?
: Do we have to know how to do these types of problems for
: the test??
: Please help me!!
: Thank you.
: Lana
The horizon plane at the North pole and the plane of the equator are parallel, separated by the radius of the earth.
When you extend these planes indefinitely far into space, they meet (by convention) at the vanishing point of perspective.
Remember, the celestial equator is out on the sky.
Horizon is defined as the plane tangent to the Earth at your position.
Yes you should know how to do any homework question for the test.
This is a question of what fraction of the area of the 5m mirron is blocked by the 1m cage.
The area of the mirror is 1/4 pi (5 squared) and the area of the cage is 1/4 pi (1 squared)
When forming the ratio to get the fraction, the 1/4's and pi's cancel out so
the ratio is (1 squared)/(5 squared) = 1/25 = 4%.
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