Science Midterms
... sun Galileo: Heliocentric system, first person to use telescope as a scientific tool by looking at the sky and making observations and recording/drawing data. Galileo’s Discoveries: 1. There are four moons orbiting Jupiter. 2. That planets are circular discs rather than points of light 3. Venus went through phases just like our moon, which meant that Venus had to be orbiting a source of light 4. The moon had many surface features: valleys, mountains, craters, etc. 5. The sun had sunspots. This allowed Galileo to estimate the sun’s rotational period. Galileo wrote the book Dialogue of the Great World Systems – an argument of a geocentric universe vs. a heliocentric one, heliocentric having more proof. Brahe: believed in geocentric universe, had extremely precise data of celestial bodies for his time. Kepler: assistant to Brahe, used all of Brahe’s data to create the three basic laws of planetary motion Newton: Stellar parallax- the apparent shift in motion of an object when viewed from two different locations. 3 Laws of Planetary Motion (may not be on midterm) 1st Law- The path of each planet around the sun is an ellipse, with the sun at the focus. 2nd Law- Equal area, equal time. Each planet revolves so that an imaginary line connecting it to the sun sweeps over equal areas in equal intervals of time. This law of equal area expresses geometrically the variations in the orbital speeds of the planet. 3rd Law- The orbital periods of the planets and their distances to the sun ARE proportional. The orbital period of revolution of ALL planets is measured in earth years. The distances to the sun for all planets is measured by the earths mean distance to the sun, or 1 AU (300,000,000 km) p^2 = d^2 Astronomy Vocabulary Circumference: the distance around a circle. Geocentric Model: Earth being center of universe and everything revolving around it Heliocentric Model: Sun being center of universe and everything revolving around it Rotation: the spinning of a body such as the earth spinning about its axis (Earth:1 day=1 rotation) Revolution: the motion of one body around another e.g. Earth around the sun (1 year=1 revolution) Retrograde Motion: An apparent westward motion of a planet on the celestial sphere with respect to the stars Epicycle: The small circle followed by a planet in the Ptolemaic theory. The center of the epicycle follows a larger circle around earth Deferent: The large circle, centered on the earth, on which the epicycle rotates according to the geocentric astronomical theory Ellipses: a curved line with the sum of the distances from (foci) to each point on the curve is constant Eccentricity: A value that defines the shape of an ellipse or planetary orbit; the ratio of the distance between the foci and the major axis. E.g. a circle has zero eccentricity Astronomical Unit: The average distance from the Earth to the Sun; 1 AU is 149,597,870 kilometers (92,960,116 miles) Light Year: The distance light travels in a year, at the rate of 300,000 kilometers per second (671 million miles per hour); 1 light-year is equivalent to 9.46053e12 km, 5,880,000,000,000 miles or 63,240 AU Equal Time Equal Area: see the 2nd Law of Planetary Motion Escape Velocity: The speed needed by an object to escape from the gravitational field of a body Aphelion: the point in Earth’s orbit when it is farthest away from the sun, July 4th Perihelion: the point in the Earth’s orbit when it is closest to the Sun, January 4th Universal law of Gravitation: Written by Sir Isaac Newton Every body in the universe attracts every other body with a force that is directly proportional to their masses and inversely proportional the square of the distance between them. Gravitational Force: More Mass = More G.F. Direct Proportion à Less Mass = Less G.F. Inverse Proportion à Less Distance = More G.F. More Distance = Less G.F. Telescopes Refracting: A telescope that uses a lens to focus light by bending it. Reflecting: A telescope that uses a mirror to focus light. Similar: Both focus light to magnify. Different: Reflecting use a mirror, refracting uses a lens Theories on the Origin of the Universe The Big Bang Theory: Theory stating that the universe DID have a beginning (unlike the Steady-State theory). States that the universe began with a giant explosion, which marks the birth of our universe. Space and time came into existence and all of the matter being created began to expand. Two Proofs 1. Edwin Hubble, famous astrologer, discovered that every galaxy is moving away from every other galaxy, thus the universe is expanding 2. Cosmic Background Radiation- leftover radiation from the Big Bang explosion found EVERYWHERE in the universe. Steady-State Theory This theory states that the universe has looked the same forever, has always existed and there was no beginning to our universe and there will be no end. This theory was developed in 1948. It was very popular in the 50’s and 60’s Closed Universe This belief is that the universe will begin to slow down because of gravity and gravity will continue to bring all matter and energy together to produce “The Big Crunch” Open Universe The idea behind this theory is that all of the matter in the universe will be so spread out from expansion that gravity will not be able to “take over.” Instead, the universe will continue to expand forever. Oscillating Theory (Cycle Theory) The idea for this theory is that “The Big Bang” would follow “The Big Crunch” and this would be a never-ending cycle. This is a universe “without end” Unit on Light Spectroscopy: The study of the electromagnetic spectrum Wavelength: distance between two successive crests Crest: top of the wavelength Trough: bottom of the wavelength Frequency: Number of wavelengths/second. Higher Number of Wavelengths = Higher Frequency Smaller Wavelength = Higher Frequency Higher Frequency = More Dangerous Radiation Speed of Light: Light speed equals 299,792,458 meters/second (186,000 miles/second). Photons: All radiat...