Universe

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It is impossible to determine who discovered Saturn, as it is one of five planets that are visible without the aid of instruments. Saturn has been widely observed by people for thousands of years, although its unique and complex system of rings are only visible using a telescope.

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  • Why did people once believe that Earth was the center of the Universe?

    Q: Why did people once believe that Earth was the center of the Universe?

    A: The belief of early astronomers that the Earth was the center of the universe stemmed from limited astronomical tools and geocentric attitudes. The Ptolemaic Model, developed around 100 A.D., presented the Earth-centered solar system in which most early Roman astronomers believed.
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  • Who discovered the planet Saturn?

    Q: Who discovered the planet Saturn?

    A: It is impossible to determine who discovered Saturn, as it is one of five planets that are visible without the aid of instruments. Saturn has been widely observed by people for thousands of years, although its unique and complex system of rings are only visible using a telescope.
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  • Do the planets travel around the sun in a path called an orbit?

    Q: Do the planets travel around the sun in a path called an orbit?

    A: Planets travel around the sun in paths called orbits. Each planet has its own orbit around the sun, and one orbit around the sun is called a year. All planets travel in the same direction around the sun.
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  • What happens after a supernova?

    Q: What happens after a supernova?

    A: Depending on the size of the star before it explodes as a supernova, the core of the star either shrinks back into a tiny neutron star or becomes a black hole. If the star is only a few times bigger than the sun, the core becomes a tiny neutron star. If the star is much bigger than the sun, the chances of it becoming a black hole are much greater.
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  • What is the temperature of a black hole?

    Q: What is the temperature of a black hole?

    A: According to NASA, the temperature of a black hole with the mass of the sun is only one ten-millionth of a degree over absolute zero. Scientists determine this by measuring the temperature of the radiation that comes from a black hole.
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  • How many modern constellations are there?

    Q: How many modern constellations are there?

    A: As of 2014, there are 41 modern constellations, which are constellations added to the catalogue after 1600. Four of them, Carina, Puppis, Pyxis and Vela are derived from Argo, a constellation catalogued by Ptolemy.
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  • What are some facts about the Aurora Borealis?

    Q: What are some facts about the Aurora Borealis?

    A: Aurora Borealis occurs when materials from the surface of the Sun collide with the atmosphere of the Earth. Experts make predictions about the occurrence of Aurora Borealis based on events taking place on the Sun and the speed of matter being thrown from the Sun's surface. Aurora Borealis is visible in portions of the Northern Hemisphere, including Canada, Scandinavia, North America, Siberia and Northern Europe.
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  • Why do some stars appear brighter than others?

    Q: Why do some stars appear brighter than others?

    A: The apparent brightness of a star viewed from Earth varies based both on the type of star and its distance from the planet. The apparent magnitude differs from a star's absolute magnitude, which describes its brightness from a set distance, rather than the varying distances of stars seen from Earth. The lower the apparent magnitude, the brighter the star is as seen from Earth.
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  • Q: What is gravitational attraction?

    A: Gravitational attraction is the force that draws two objects together. It is governed by the law of universal gravitation, which states that the force of attraction between two objects is related to the mass of the objects and inversely related to the distance between the two.
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  • Q: What does the Milky Way Galaxy look like?

    A: The Earth's home galaxy, the Milky Way, is known as a spiral galaxy because of its shape when viewed face-on. If seen edge-on, the galaxy would appear to be a flat disk-like structure.
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  • Q: What is the best estimate scientists have made of the physical size of the universe?

    A: The best estimate of scientists trying to quantify the size of the universe place estimates on the observable portion at 46 billion light years from earth to the observable edge, or approximately 91 billion light years in diameter. However, there are some fundamental flaws with this approach.
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  • Q: Why is outer space dark?

    A: Outer space appears dark at night for multiple reasons, the most simple being that the nearest light source, the sun, is blocked by the earth, creating darkness. Outside Earth's atmosphere, outer space appears dark instead of blue because the sun's light is not refracted by atmospheric gases.
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  • Q: Why can't we see past the cosmological horizon?

    A: It's impossible to look beyond the cosmological horizon because this horizon represents the distance that light has traveled since the big bang. The cosmological horizon exists because the speed of light is constant and all electromagnetic waves travel at the same speed. Therefore, the cosmological horizon holds for visible light as well as for other types of waves, such as radio or microwaves.
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  • Q: How far is the edge of space from Earth?

    A: The edge of space is generally recognized internationally to be at the Kármán Line, which is 62 miles from the surface of Earth. While the exact boundary of space is open to interpretation, this is the definition recognized by the Federation Aeronautique Internationale and National Aeronautics and Space Administration.
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  • Q: How does gravity hold the universe together?

    A: Gravity holds the universe together by keeping the large bodies that make up the universe together. It keeps the Earth in orbit around the sun, the sun in orbit around the center of the Milky Way and the Milky Way bound to other nearby galaxies known as the Local Group.
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  • Q: Are there other universes out there?

    A: There is no definitive answer as to whether other universes exist, although many astronomers believe it is highly likely and have several theories on how or where they exist. Some people theorize that an infinite number of universes could have formed following the Big Bang, with each one having its own laws of physics.
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  • Q: How do you make a model of a solar system?

    A: One of the easiest ways to make a model of a solar system is to cut circles from cardboard to represent the planets and hang them in orbits from a larger circle. Use nine circles to represent the eight planets and the sun.
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  • Q: What is the ultimate fate of an open universe?

    A: Although the ultimate fate of the universe is a largely debated topic, according to the University of Tennessee, in an open universe the universe will continue to expand forever. This is due to insufficient mass to cause the expansion to stop.
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  • What types of information about space are interesting to children?

    Q: What types of information about space are interesting to children?

    A: The type of information about space that is interesting to children includes the number and nature of the planets, the different objects in the universe and the size and nature of the sun. Children find it fascinating to learn that the sun is actually a star that sits at the centre of the solar system. The sun's diameter is 110 times bigger than the earth's and that the sun alone makes up over 99 percent of the solar system's mass.
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  • Q: What is Ptolemy's universe theory?

    A: Greek philosopher Claudius Ptolemy believed that the sun, planets and stars all revolved around the Earth. This belief gave way to the ancient Greek theory of a geocentric or Ptolemaic model of the universe. "Geocentric" refers to the belief that the Earth is the center of the universe.
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  • Q: What is Kepler's Universe Theory?

    A: Johannes Kepler's theories of the universe were notable for hypothesizing that the universe was created on April 27, 4977 B.C. and that the planets orbit in an elliptical pattern rather than a circular pattern. His theory superseded previous theories which postulated that planets move in circular orbits at constant speeds.
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