| A | B |
|---|
| Geocentric | In a geocentric system, Earth is at the center of the revolving planets. |
| Heliocentric | In a heliocentric system, Earth and the other planets revolve around the sun. |
| Ptolemy | (toll-a-me) A.D. 140 astronomer who explained that the Earth was at the center and the planets and sun revolved around Earth. |
| Copernicus, Nicolaus | An early 1500s Polish astronomer who developed a sun-centered explanation called the heliocentric system where the planets all rotate around the sun. |
| Galileo, Galilei | 1600s Astronomer supported the heliocentric model of the solar system with his discovery (using his telescopes) of the four moons revolving around Jupiter and the phases of Venus. |
| Brahe, Tycho | In the late 1500s this Danish astronomer made accurate records of his observations of the the planets positions for over 20 years. |
| Kepler, Johannes | 1600 German mathematician analyzed Brahes data and discovered that the planets orbited the sun in an elliptical pattern. |
| Newton, Isaac | English scientist explained how the planets stayed in orbit because of two combined factors: inertia and gravity. |
| Inertia | A moving object will continue to move in a straight line and a stationary object will remain in place until some force affects a change. |
| Mass and inertia | The more mass an object has, the greater its inertia. |
| Gravity | The attraction of objects to each other. |
| Mass and gravity | The greater the mass, the greater the gravity. |
| Suns energy | The suns energy comes from nuclear fusion. |
| Nuclear fusion | Hydrogen atoms join together to form helium and in the process release large amounts of heat and light. |
| Core | The center of the sun, measuring 15 million degrees Celsius, where nuclear fusion happens. |
| Suns atmosphere | The suns atmosphere has three layers: the photosphere, the chromoshpere, and the corona. |
| Photosphere | The inner layer of the suns atmosphere that produces the light. (photos means light) visible in photographs |
| Chromosphere | The middle layer of the suns atmosphere produces a reddish glow. chromos = color visible at the beginning and end of an eclipse |
| Corona | The outer layer of the suns atmosphere appearing like a halo, corona = crown visible only during eclipses or with special telescopes |
| Solar wind | A stream of electrically charged particles emanating from the corona |
| Features on the Sun | Features on the sun include sunspots, prominences, and solar flares |
| Sunspots | Areas of gas on the sun that are cooler than the gases around them. 11 year sunspot cycle may be linked to short term climate changes on Earth |
| Prominences | Reddish loops of gas linking different parts of sunspot regions |
| Solar flares | Explosions of hydrogen gas when the solar prominences connect that greatly increase the solar wind particles that reach Earths atmosphere. |
| Magnetic storms | Storms caused by the interaction of solar winds and earths magnetic field that can disrupt radio, television, telephone and even electrical service. |
| Inner planets | Small, rocky surfaces, inside the asteroid belt |
| Terrestrial planets | Planets with rocky surfaces. terra means earth |
| Mariner 10 | 1974 probe that photographed half of Mercurys surface. |
| Retrograde rotation | Venus is the only inner planet with clockwise rotation. Retrograde means moving backward All other inner planets have counter clockwise rotations. (They rotate in the direction of their orbit around the sun. |
| Greenhouse effect | The trapping of heat by the heavy carbon dioxide atmosphere on Venus makes it 460°C! |
| Gas giants | Name of the first four outer planets due to their immense size and gas atmospheres |
| Comet | Chunks of ice and dust that orbit the sun in long, narrow elipses |
| Asteroids | Giant chunks of rock that orbit the sun in the asteroid belt |
| Asteriod belt | An area between mars and Jupiter that has thousands and thousands of asteroids. |
| Meteoroid | A chunk of rock or dust in space that has originated from a comet or asteroid. |
| Meteor | The streak of light seen in the night sky when the friction of falling through Earths atmosphere burns up smaller meteroids |
| Meteorites | Meteors that pass through Earths atmosphere and hit Earths surface. |
| Craters | The craters on the moon and Earth were caused by large meteorites or small asteroids. |
| Goldilocks Conditions | Earth has liquid water, a suitable temperature range and atmosphere for living things to survive. |
| Extraterrestrial life | Life other than that on Earth. |
