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OUTCOME QUESTION(S): S1-4-04: What evidence is there that the sun is the centre of our solar system? S1-4-05: How does the position and motion of Earth produce day/night, the phases of the moon, and the seasons? Vocabulary & People PtolemyCopernicusGalileo KeplerRetrogradeGeocentric HeliocentricSolsticeEquinox

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Ptolemy (100 AD) Summarized naked-eye observations and knowledge of that time Earth was centre of the universe - Geocentric In good with the Church Observation: Some planets seem to move backwards in orbits: Retrograde motion Planet is Greek for wanderer

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Ptolemy GEOCENTRIC Ptolemys proposed mini-loops were called epicycles

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Copernicus (1473) Produced mathematical evidence for a Sun- centered system heliocentric Easily explained retrograde motion Proved Earth rotated on its axis once daily and revolved around the sun once yearly Not in good with Church Called the Founder of modern astronomy

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Copernicus HELIOCENTRIC

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First optical telescope made in Netherlands (1608): The first one was a simple refracting telescope Uses curved optical elements Gathers and collects light to a focal point Increase apparent size and apparent brightness

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Telescopes are classified by the energy detected: Optical visible light Infrared heat energy Ultraviolet, X-ray Different energies provide astronomers with different information a Refracting telescope - lenses focus an image b Reflecting telescope - mirrors focus an image

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Galileo (1564) Perfected the telescope (built a few years earlier) First to state and use the scientific method Discovered moons around Jupiter 1 Proof that not all objects traveled around Earth Venus had phases (day/night) like Earth 2 Proof that it traveled around the Sun Not in good with the Church

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Galileos drawings and scientific records of his observations

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Would not recant his work as a mistake and spent life under house arrest Galileo published his book confirming Copernicus mathematics, and was accused of heresy by the Church. By the way, Pope John Paul II made a public apology and exonerated Galileo in 1992

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Kepler (1571) Brahe built one of the best observatories in the world Worked as assistant for astronomer, Tycho Brahe Brahes goal was to prove Copernicus incorrect Measured positions of 777 stars and five planets that were known at that time He received loads of money from the Church in hopes he could prove the Earth-centred viewhe failed

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Kepler used Brahes data after his death to describe three laws of planetary motion: 1. Planets orbit the Sun in ellipses 2. Planets move faster close to Sun, and slower farther away 3. Planets farther away have a longer orbit

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The Earth rotates on its axis once a day. At any time - half of Earth is in day and half in night. Earth rotates towards the East The Earth revolves around the Sun once a year. At any time - half of Earth is in winter and half in summer. summer winter

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Time-lapse photography to show the stars spinning as we rotate on our axis

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Our axis is tilted at 23.5 o (degrees) This tilt and the curvature of the Earth is responsible for the variations in the Suns energy and creates our seasons.

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Summer direct energy Winter indirect energy Summer: not only more direct but also more hours of the Suns energy Summer Solstice (June 21) Longest Day Winter Solstice (Dec 21) Shortest Day Fall Equinox (Sept 22) 12h and 12h Spring Equinox (Mar 21) 12h and 12h

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Moon completes 1 rotation on its axis in the same time as it completes 1 revolution around the Earth (synchronous) We always see the same side facing the Earth Orbit is elliptical Tilted 5 Mean Distance: 384,400 km Moon Rotation Thats why there is a dark side of the Moon

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Phases of the Moon Shines only by reflected sunlight Depends on fraction of sunlit half visible to us

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CAN YOU ANSWER THESE QUESTIONS? S1-4-04: What evidence is there that the sun is the centre of our solar system? S1-4-05: How does the position and motion of Earth produce day/night, the phases of the moon, and the seasons? Vocabulary & People PtolemyCopernicusGalileo KeplerRetrogradeGeocentric HeliocentricSolsticeEquinox