Chapter 1
Our Place in the Universe
What is our place in the Universe?
How did we come to be?
How can we know what the Universe was like in the past?
Can we see the entire Universe?
Star
A large, glowing ball of gas that generates heat and light through nuclear fusion.
Planet
A moderately large object that orbits a star, it shines by reflected light. Planets may be rocky, icy, or gaseous in composition.
Asteroid
A relatively small and rocky object that orbits a star.
Comet
A relatively small and icy object that orbits a star.
Solar (Star) System
A star and all the material that orbits it, including its planets and moons.
Nebula
An interstellar cloud of gas and/or dust.
Galaxy
A great island of stars in space, all held together by gravity and orbiting a common center.
(A black hole is at the center of the Milkyway Galaxy)
Universe
The sum total of all matter and energy, that is, everything withing and between all galaxies.
How did we come to be?
The expansion of the Universe began with the hot and dense Big Bang. The universe continues to expand, but on smaller scales gravity has pulled matter together to make galaxies.
The Universe only contained two chemical elements: Hydrogen and Helium
All other elements were created by stars within galaxies.
(We came from stars)
Light-Year
The distance light can travel in 1 year.
Light travels at a finite speed(300,000 km/s)
About 10 trillion kilometers(6 trillion miles)
No we can't see the entire Universe.
1 comment:
Beautiful work!
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