Early Models of the Universe PDF

Early Models of the Universe JUMBLED WORDS RAST XAGLYA NLSETPA ONOM TSONYMARO ▪ During ancient times, Earth was perceived to be flat. ▪ Early Babylonian, Chinese, Egyptian, and Hebrew civilizations believed that Earth had corners. ▪ It was then believed that if you set to sail straight in the...

Early Models of the Universe JUMBLED WORDS RAST XAGLYA NLSETPA ONOM TSONYMARO ▪ During ancient times, Earth was perceived to be flat. ▪ Early Babylonian, Chinese, Egyptian, and Hebrew civilizations believed that Earth had corners. ▪ It was then believed that if you set to sail straight in the ocean, you would get to the edge of Earth and fall. The Earth ▪Flat Earth map drawn by Orlando Ferguson in 1893. The map contains several references to biblical passages as well as various jabs at the "Globe Theory". ▪However, many philosophers theorized that Earth was round and not flat. ▪Navigators such as Ferdinand Magellan (1480-1521) and ▪Juan Sebastian Elcano (1476-1526) were given credit for circumnavigating the world and proving that Earth is not flat. How did the idea of Spherical Earth evolve? Greek philosophers also investigated on the shape of Earth. Philosophers like Plato (428 BCE – 348 BCE) and Aristotle (384 BCE – 322 BCE) described Earth and the heavens as spherical. In fact, Eudoxus of Cnidus (400 BCE – 350 BCE ) constructed a planetary model based on this. Then around 6 BCE, these Greek philosophers speculated that Earth was actually spherical. ▪The timeline shows the ideas of some Greek philosophers, including Pythagoras (570 BCE – 490 BCE) and Eratosthenes (276 BCE – 194 BCE), about the sphericity of the Earth. Pythagoras (started the idea of the spherical Earth) Plato (educated his students on the sphericity of the Earth but made no justifications) Aristotle ( noted that there were stars in Egypt that could be seen on the other parts of the Earth. This phenomenon was only possible if Earth had a curved surface. Eratosthenes (estimated the circumference of the Earth. Pythagoras (started the idea of the spherical Earth) Plato (educated his students on the sphericity of the Earth but made no justifications) Aristotle ( noted that there were stars in Egypt that could be seen on the other parts of the Earth. This phenomenon was only possible if Earth had a curved surface. Eratosthenes (estimated the circumference of the Earth. Different Models of the Universe ▪Before the telescope was invented, ancient astronomers only used their unaided eyes to observe the sky and the stars. ▪Eventually they created models of the universe. Eudoxus of Cnidus (400 BCE – 355 BCE) He was considered as the first astronomer to explain the retrograde motion of the planets in the sky. He found out the differences in the motion of each planet that should be considered to give an accurate description of the universe. What is retrograde motion? ▪Retrograde motion is an APPARENT change in the movement of the planet through the sky. ▪Watch this video to fully understand retrograde motion. ▪According to Eudoxus’s model, the universe was composed of Earth, five other planets (that are visible with the unaided eye, namely Mercury, Venus, Mars, Jupiter, and Saturn) Aristotle’s Model ▪Aristotle somehow patterned his model to the model of Eudoxus. ▪Aristotle’s model showed that the universe was spherical and finite. ▪Just like Eudoxus, he perceived Earth was at the center of the universe and was stationary. ▪He believed so because Earth is too big to move; thus it could not rotate. ▪Other celestial bodies were built up symmetrically in concentric spherical rings around the earth ▪Aristotle believed that the Earth was composed of four elements – Earth, Water, Air, and Fire. ▪Beyond Earth are the planets and the moon which revolved in spherical rings. ▪He further described that each ring was in physical contact with one another, which means the motion of a heavenly body in one sphere will affect the motion of a nearby heavenly body. Aristarchus of Samos model 310 BCE – 230 BCE ▪He was a Greek astronomer who made the first attempt to create a heliocentric model of universe, which places the sun and the fixed stars were at rest, while Earth revolved around the sun in a circular path. ▪The only book that survived was entitiled On the Sizes and Distances of the Sun and the Moon. ▪In this book, Aristarchus calculated the sizes of the sun, and the moon and their distances from Earth by estimating the relative angles of the moon and the sun from Earth. ▪Aristarchus had 3 assumptions: a. Earth was spherical b. It is far from the sun c. Moon passes through the Earth’s shadow when they align. ▪Do you believe that the astronomical positions of the stars and planets influence or affect human lives and events on Earth? Why or Why not? Claudius Ptolemaeus 100 AD – 178 AD ▪Ptolemaic universe. ▪In this model, it is assumed that Earth was at the center of the universe, while the other celestial bodies revolved around the Earth in perfect circles with constant velocity. ▪Ptolemy’s model was considered more refined than previous geocentric models because his model could explain the motion of the celestial bodies accurately. ▪Ptolemy assumed that planets revolved on epicycles (small spheres) which moved around the deferent (large sphere). ▪He added that the stars belonged to the celestial sphere which was located beyond the planetary spheres. ▪The center of the deferent is called the eccentric. ▪What Ptolemy did next was to “move” Earth from its original position to a position below the center of the system that is still inside the deferent. Nicolaus Copernicus (1473-1543) ▪ During the 16th century, a Polish astronomer, revived the heliocentric model of Aristarchus. ▪ He was hesitant to publish his findings because he was afraid of condemnation. ▪ But it was published a year before his death. ▪Copernicus strongly believed in the heliocentric model because there were loopholes in the Ptolemaic model in terms of predicting the positions of the planets. ▪The Copernicus’s ▪ In Copernicus’s model shown above, it could be concluded that: 1. Heavenly bodies exhibited constant circular and perpetual motion along their epicycles. 2. The sun was at the center of the universe. 3. The order of planets from the sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn and beyond the planets were fixed stars. Tycho Brahe (1546-1601) ▪Tycho Brahe was a Danish astronomer who also made planetary observations. ▪Unlike Copernicus, Brahe Believed in a geocentric universe, but his idea of the geocentric universe is slightly different from Ptolemy’s ▪In Brahe’s model of the universe, called the “Tychomic system”, Earth was at the center and the sun and the moon revolved around it, and all the other planets orbited the sun. Such a model was a type of “geoheliocentric system”. JOHANNES KEPLER (1571-1630) is oval. Planetary orbit Sun is at one focus of the oval. The planet’s velocity is not constant.