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Period: 276 BCE to 194 BCE
Erastothenes's lifetime
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240 BCE
Discovery of the Earth's Circumference
Eratosthenes then measured the angle of a shadow cast by a stick at noon on the summer solstice in Alexandria and found it made an angle of about 7.2 degrees or about 1/50 of a complete circle.
A huge breakthrough in Spatial understanding, as it was disputed whether or not the earth was round at the time. Using simple geometry and trigonometry and by recognizing Earth as a sphere in space, Eratosthenes cemented his place in history. -
Period: 100 to 170
Claudius Ptolemy's lifetime
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150
The Almagest
Astronomical manual written around 150 AD by Ptolemy.
It served as the basic guide for Islamic and European astronomers until about the beginning of the 17th century.
Included many of Ptolemy's contributions to mathematics and astronomy such as the Ptolemaic system, a geocentric system that postulated that the apparently irregular paths of the Sun, Moon, and planets were actually a combination of several regular circular motions seen in perspective from a stationary Earth. -
Period: 1473 to 1543
Nicolaus Copernicus's Lifetime
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1543
Heliocentric Model
The astronomical model in which the Earth and planets revolve around the Sun at the center of the Universe. Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center. Copernicus probably adopted the theory sometime between 1508 and 1514 but only proposed the book until 1543, two months before he died.
This model was important because it went against the Geocentric model established by Ptolemy and enforced by the Catholic Church. -
Period: 1546 to
Tycho Brahe's lifetime
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Period: 1571 to
Johannes Kepler's Lifetime
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Tychonic system
The scheme for the structure of the solar system put forward in 1583 by the Danish astronomer Tycho Brahe.
Combined what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system.
Important because it provided explanations for phenomena that Ptolemaic models never did.
EX. || explained the observed variations of phase of Venus, for which the Ptolemaic system had no explanation || -
Kepler's Laws of Planetary Motion
Derived by the German astronomer Johannes Kepler, Kepler's laws of planetary motion mark an important turning point in the transition from geocentrism to heliocentrism. They provide the first quantitative connection between the planets, including Earth. -
Period: to
Sir Isaac Newton's lifetime
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Newton's Law of Universal Gravitation
The law states that all objects attract each other with a force that is directly proportional to the product of their masses and inversely proportional to their distance of separation.
Newton proved that the same laws that govern motion on Earth also work in the heavens—what we now call “space” or “the cosmos”. His were the first “universal laws”, that are known to apply everywhere in the universe. Physics is now full of these—including Quantum Physics and Relativity -
Period: to
Albert Einstein's lifetime
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Einstein's Theory of Relativity
Albert Einstein, in his theory of relativity, determined that the laws of physics are the same for all non-accelerating observers, and he showed that the speed of light within a vacuum is the same no matter the speed at which an observer travels.
The theory explains the behavior of objects in space and time, and it can be used to predict everything from the existence of black holes, to light bending due to gravity, to the behavior of the planet Mercury in its orbit.