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A millennium ago, American Indian tribes built villages
and cities with astronomical connections across the United States. |
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The priests and pharaohs of ancient Egypt established
their own cosmic order. |
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A source of information on the life and work of
Galileo Galilei (1564-1642) and the science of his time. |
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The proper motion of a star is its apparent angular
movement per year on the celestial sphere. It is a combination
of its actual motion through space and its motion relative to
the solar system. Most stars are so distant that the proper motion
is almost negligible on a human time scale. |
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A look at the size and scale of things in the universe. |
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As the earth moves around the sun, a foreground
(or nearer) star will change position relative to the background
of more distant stars. |
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Our clocks are based on the solar day and the Sun
appears to drift eastward with respect to the stars (or lag behind
the stars) by
about 1 degree per day. |
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What keeps the planets in their elliptical orbits?
Newton's answer was that a fundamental force
called "gravity" operating between all objects made
them move the way they do. |
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The laws of physics are the same for every inertial
observer. By observing the outcome of any
experiment, one cannot distinguish a state of rest from a state
of constant velocity. |
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No physical experiment can distinguish a uniformly
accelerating reference frame (relative to an inertial frame) from
an inertial reference frame with a uniform gravitational field. |
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The phenomena referred to as "light" range
from radio through X-rays, and beyond. . . |
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At least 95% of the celestial information we receive
is in the form of light. |
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The hotter an object gets, the brighter it glows.
Its color changes from red to orange, to yellow, and so on, eventually
becoming blue (or beyond) |
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Each element has its own unique "light signature"
in the production or absorption of light. |
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The ability of a telescope to collect a lot more
light than the human eye, its light-gathering power, is probably
its most important feature. |
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The power source of the stars! |
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If we want to learn about stars, let's start by
studying the one closest to us. |
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An introduction. . . |
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How do we learn about the stars? What can we find about the
stars? |
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An example of celestial violence and change is the birth of
stars. |
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Stars live for a very long time compared to human lifetimes. |
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A brief introduction to stellar evolution. |
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Stars live for a very long time compared to human lifetimes. |
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Stars evolving and dying? These are strange concepts. |
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All that is left of the star after the outer layers are ejected
to space is the core remnant. |
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The idea that space and time can be curved, or warped, is fairly
recent. |
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Neutron stars are the collapsed cores of some massive stars.
They pack roughly the mass of our Sun into a region the size of
a city. |
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Ever wonder what it would look like to travel to a black hole?
A neutron star? |
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Cosmology is the study of the origin, current state, and future of our Universe. |
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Cosmology observations and some implications |
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Rarely will you find a subject more interesting than cosmology. . . |
