Team A: The Earth is flat

Transcription

1 Team A: The Earth is flat You are scientists and philosophers in Europe in the Middle Age. Your team will argue in favor of the flat model of Earth. In many ancient cultures (Greece, India, China), the conception of Earth s shape is a disk or a plane. The Egyptians and Mesopotamian thought that the world was portrayed as a disk floating in the ocean, where the sky is a solid dome with the Sun, Moon, planets and stars embedded in it. Arguments for this view of the Earth came from observation of the world around us, in particular the fact that the surface of water is always flat/horizontal, wherever we are on Earth. To account for the fact that the Sun does not rise and set at the same time for everyone, the Greek philosopher Archelaus believed that the flat Earth was curved in the middle like a saucer. The Roman poet Lucretius opposed the concept of a spherical Earth, because he thought the idea of animals walking around upside down under the Earth was absurd. Source: Wikipedia ( Embedded Intégrés A saucer Une soucoupe

2 Team B: The Earth is spherical You are scientists and philosophers in Europe in the Middle Age. Your team will argue in favor of the spherical model of Earth. Pythagoras in the 6th-century BC was the first to state that the Earth is spherical, although he provided no arguments. Aristotle, in the 4th-century BC, provided physical and observational arguments supporting the idea of a spherical Earth, such as the shadow casted by the Earth on the Moon during a lunar eclipse, or the comparison of visible stars in the Northern and Southern hemisphere skies. The Greek geographer Strabo put forward another argument in favor of the spherical Earth by observing ships reaching the horizon (see below). Eratosthenes, a Greek astronomer, was the first to estimate Earth's circumference. He had heard that in Syene the Sun was directly overhead at the summer solstice whereas in Alexandria it still cast a shadow. Using the differing angles the shadows made as the basis of his trigonometric calculations he estimated a circumference of the Earth. Source: Wikipedia ( To state Déclarer To cast: Jeter/projeter To put forward: Avancer Overhead Au-dessus

3 Team A: The Earth is at the center of the planetary system You are scientists in Europe in the 16 th century. Your team will argue in favor of the geocentric system. In astronomy, the geocentric system is a description of the Universe with Earth at the center, and where the Sun, the Moon, other planets and stars orbit the Earth. This view was promoted in ancient times by Aristotle and Ptolemy. Two observations supported the idea that Earth was the center of the Universe. First, from the view on Earth, the Sun appears to revolve around Earth once per day (it rises, goes up in the sky and then sets). While the Moon and the planets have their own motions, they also appear to revolve around Earth about once per day. The stars appeared to be on a celestial sphere, rotating once each day along an axis through the north and south geographic poles of Earth. Second, Earth does not seem to move from the perspective of an Earth-bound observer; it appears to be solid, stable, and unmoving. Source: Wikipedia ( To revolve around : Tourner autour Earth-bound observer : An observer standing on the Earth

4 Team B: The Sun is at the center of the planetary system You are scientists in Europe in the 16 th century. Your team will argue in favor of the heliocentric system. In astronomy, the heliocentric system is a description of the Universe with Sun at the center, and where the Earth, the Moon and other planets orbit the Sun. It was first presented during the Renaissance by mathematician and astronomer Nicolaus Copernicus. This theory resolved the issue of planetary retrograde motion such as the motion of Mars, which seems to go back on its tracks in the sky, by arguing that such motion was only perceived, rather than real: it was a visual effect, as an object that one is passing seems to move backwards against the horizon. In the following century, Johannes Kepler expanded this model to include elliptical orbits, and Galileo Galilei presented supporting observations (phases of the Moon and of Venus) made using a telescope. Source: Wikipedia ( To resolve: Résoudre To go back on one s tracks: Revenir sur son chemin Supporting: Soutenant

5 Team A: Our Galaxy is one of many in the Universe. You are astronomers in the US in 1920, followers of Heber Curtis. Your team will argue in favor of the Milky Way being one galaxy among many others. In the early part of the twentieth century there was much disagreement between astronomers about the structure and size of the Universe. The leaders of the two opposing views were two American astronomers, Heber Curtis and Harlow Shapley. Curtis believed that our galaxy was only part of a much, much larger Universe. He stated that the galaxy had a diameter light years with Sun very near its center. He based his ideas on star counts and measurement of stellar brightness (the further away a star is, the dimmer it looks), taking into account the idea that the further away you look, the more dust there is between you and a star (thus the star will look even dimmer than it would by just being far away). He also argued that the newly discovered spiral nebulae (see image) such as Andromeda were island universes outside our galaxy, a suggestion first made by Kant in the mid- 18th century. He showed that there were more novae (remnants from the death of a star) in Andromeda than in the Milky Way, asking why there would be more novae in one small section of the galaxy than in the other sections, if Andromeda was within the Galaxy. Source: Wikipedia ( To state Déclarer Brightness: Luminosité Dim: Sombre Remnant: Vestige

6 Team B: Our Galaxy is the whole Universe. You are astronomers in the US in 1920, followers of Harlow Shapley. Your team will argue in favor of the Milky Way being the whole Universe. In the early part of the twentieth century there was much disagreement between astronomers about the structure and size of the Universe. The leaders of the two opposing views were two American astronomers, Heber Curtis and Harlow Shapley. Shapley stated that out galaxy was the whole universe, that it had a diameter light years and that the Sun was at its edge. He based his idea on the fact that the further away a source of light is located, the dimmer it looks. Therefore, by looking at the brightness of stars, one can determine the size of the Galaxy. He argued that the spiral nebulae (see image) such as Andromeda, then recently discovered, were in fact gas clouds within the galaxy. He backed up this claim by citing relative sizes: if Andromeda were not part of the Milky Way, then its distance must have been on the order of 10 8 light years. This distance was, at the time, thought to be way too large. Source: Wikipedia ( To state Déclarer Dim: Sombre Brightness: Luminosité To back up: Soutenir/appuyer