Universe

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The Big Bang theory states that the universe began with a massive explosion approximately 13.7 billion years ago. All matter was concentrated in a single point of extremely hot, dense matter. This exp…

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The observable universe is the portion of the entire universe that scientists can see and measure using telescopes and other instruments. It has a radius of approximately 93 billion light-years across…

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The universe's composition: Ordinary atoms and luminous matter = 4%, Dark matter = ~27%, Dark energy = ~69%. Dark matter is invisible matter detected through gravitational effects on visible matter. I…

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A galaxy is a massive collection of gas, dust, billions of stars, and their solar systems held together by gravity. Galaxies are the fundamental building blocks of the observable universe. Scientists …

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The three main galaxy types are: 1) Spiral galaxies - flat, rotating discs with curved arms extending from a central bulge (example: Milky Way). 2) Elliptical galaxies - oval or elongated shapes, rang…

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The Milky Way is a spiral galaxy containing approximately 100 billion stars. Its diameter is about 100,000 light-years. It appears as a milky band of light across the night sky (hence the name). Our s…

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Andromeda is our nearest galactic neighbor, located approximately 2.5 million light-years from Earth. If we traveled at Earth's current orbital speed around the Sun (30 km/s), it would take approximat…

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Stars are composed primarily of hydrogen and helium gases in a superheated state called plasma. Stars produce energy through nuclear fusion - hydrogen atoms fuse together to form helium atoms under ex…