Universe

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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: Is the universe expanding?

    A: The universe has been known to be expanding since 1929, when Edwin Hubble measured the speed at which distant galaxies appear to be receding from Earth's position in space. In the early 21st century, astronomers measured the rate of expansion and discovered that it is increasing.
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  • Q: What is the function of the solar plexus?

    A: The solar plexus, or celiac plexus, is a large cluster of nerves that relay messages from the major organs of the abdomen to the brain. These organs, called visceral organs, are important to metabolism and to general life functioning. The solar plexus monitors them and makes sure they are functioning correctly.
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  • Q: How do you know the world might be ending?

    A: Scientists postulate that the end of the world could stem from a variety of sources, including destruction by meteor, overpopulation and war that affects the entire globe. Dysgenics, or the possible decay of human genes, nuclear warfare and climate change are other scenarios that scientists study and that may predict the end of the human species. Although some scenarios include the end of both the planet and the human race, others suggest that the planet and other forms of life are likely to continue to exist following the extinction of humans. A global pandemic, possibly due to a virus or an antibiotic-resistant bacteria, is thought to be the only cause of extinction that would affect humans alone.
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  • Q: Are humans alone in the universe?

    A: Whether humans are the only intelligent life to have evolved in the universe cannot be answered with certainty, but a probability can be assigned to the proposition. Accurately estimating the number of advanced civilizations in existence is done by assessing the number of opportunities for intelligent life to evolve and contrasting that with the improbability of various stages in the development of a civilization.
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  • Q: What is diurnal motion?

    A: In astronomy, the term "diurnal motion" refers to the movement of stars around the Earth's celestial poles due to the planet's rotation on its axis. This movement is called a diurnal circle.
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  • Q: What makes up the universe?

    A: The universe is made up of ordinary matter, dark matter and dark energy. Only 4.6 percent of the universe is made from ordinary atoms, the other 95.4 percent is composed of matter that humans cannot see.
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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: 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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  • How many solar systems are there?

    Q: How many solar systems are there?

    A: The exact number of solar systems is not known. According to NASA, there are more than 100 billion galaxies within the universe. One of these galaxies is the Milky Way galaxy, where our solar system is located.
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  • Q: Who discovered the first black hole?

    A: In science, if something isn't directly observable it can't be "discovered." There is only indirect evidence of black holes. The existence of black holes has been a topic of speculation for hundreds of years, but John Wheeler is credited with coining the term, "black hole," in 1969.
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  • Q: Did the idea of a heliocentric view of the solar system originate with Copernicus?

    A: The ancient Greek astronomer and mathematician known as Aristarchus of Samos was the first person to propose a heliocentric view of the solar system. He lived circa 310 B.C. to 230 B.C. and stated that the Earth, like other planets, orbited the sun, which he regarded as the universe's center.
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  • Q: What is the smallest star in the universe?

    A: As of May 2015, the smallest known star in the universe is 2MASS J05233822-1403022. This star has a brightness that is 1/8,000 the brightness of the sun. Its diameter is 0.09 times that of the sun, making it smaller than Jupiter.
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  • Q: What are the differences between the solar system and the Milky Way Galaxy?

    A: The solar system is a system in the universe that is comprised of the Sun, eight official planets, three dwarf planets and approximately 130 satellites of the planets, according to Nine Planets. Besides these bodies, the solar system also has numerous comets and asteroids, which are smaller. On the other hand, the Milky Way is the galaxy within which the solar system falls.
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