Chapter 8 Summary Document.docx

**Chapter 8:** **Earth, the Solar System, and the Universe** **Lesson 1: Earth and Sun** **Key Ideas/Facts:** - **Gravity:** \"Gravity is a force of attraction, or pull, between any two objects.\" The strength of gravity depends on mass and distance. - **Orbit:** \"An orbit is the p...

**Chapter 8:** **Earth, the Solar System, and the Universe** **Lesson 1: Earth and Sun** **Key Ideas/Facts:** - **Gravity:** \"Gravity is a force of attraction, or pull, between any two objects.\" The strength of gravity depends on mass and distance. - **Orbit:** \"An orbit is the path one object takes around another object.\" Earth is held in orbit around the Sun by gravity and inertia. - **Inertia:** \"Inertia is the tendency of a moving object to keep moving in a straight line.\" Inertia prevents Earth from being pulled directly into the Sun by gravity. - **Revolution:** \"A revolution is one complete trip around the Sun.\" Earth\'s revolution around the Sun takes one year and, combined with Earth\'s axial tilt, causes the seasons. - **Seasons:** Caused by the tilt of Earth\'s axis (23°) and the changing angle at which sunlight strikes different parts of Earth as it revolves around the Sun. \"When the Northern Hemisphere is tilted away from the Sun...this is winter.\" - **Rotation:** \"One rotation is a complete spin on the axis.\" Earth\'s rotation takes 24 hours and causes day and night. \"At any point in time, half of Earth\'s surface faces the Sun and is in daylight. The other half of Earth\'s surface faces away from the Sun and is in darkness.\" **Lesson 2: Earth and Moon** - **Moon\'s Surface:** Lacks an atmosphere and has extreme temperature variations. \"Temperatures can reach as high as 253°F (123°C) and drop below -451°F (-233°C).\" The surface is characterized by craters, maria (plains), rills (valleys), and mountains. - **Phases of the Moon:** \"A phase of the Moon is the appearance and shape of the Moon as you see it at a particular time.\" These are caused by varying amounts of sunlight reflecting from the Moon\'s surface as it orbits Earth. - **Eclipses: Solar Eclipse:** \"A solar eclipse occurs when the Moon passes directly between Earth and the Sun.\" Can only occur during a new moon. - **Lunar Eclipse:** \"A lunar eclipse occurs when the Moon moves into Earth\'s shadow and is no longer reached by direct sunlight.\" Can only occur during a full moon. - **Tides:** \"The pull of gravity between Earth and the Moon and between Earth and the Sun causes...the tide, or the rise and the fall of the ocean\'s surface.\" High tides occur on the side of Earth facing the Moon and the opposite side. Spring tides occur during new and full moons, while neap tides occur during first and last quarter moons. **Lesson 3: The Solar System** - **Telescopes:** \"A telescope is an instrument that makes distant objects seem larger and nearer.\" Optical telescopes use lenses or mirrors; radio telescopes record radio waves. Space telescopes, like the Hubble Space Telescope, avoid atmospheric interference. - **Planets:** \"A planet is a large object that orbits a star.\" The eight planets in our solar system, in order from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Inner planets are terrestrial; outer planets are gas giants. - **Moons/Satellites:** \"A moon is a natural object that orbits a planet.\" Moons are also called satellites. Artificial satellites are man-made objects orbiting planets. - **Other Objects: Comet:** \"A comet is a mixture of frozen gases, ice, dust, and rock that moves in an elliptical orbit around the Sun.\" - **Space Exploration:** Space probes are vehicles sent to explore objects in space. Astronauts have only explored the Moon. Rovers have been sent to Mars. **Lesson 4: Stars and the Universe** - **Star Formation:** Stars form from nebulae, huge clouds of gas and dust. Gravity pulls the matter together, leading to nuclear fusion and the birth of a protostar. - **Star Cycle:** Stars progress through stages (e.g., red giant, white dwarf) based on their mass. Massive stars can end their lives as supernovas or black holes. \"A black hole is an object that is so dense and has such powerful gravity that nothing can escape from it, not even light.\" - **Constellations:** \"A constellation is a group of stars that appear to form a pattern.\" Used for navigation. - **Light-Year:** \"A light-year is the distance that light travels in a year, or about 9.5 trillion km (5.9 trillion mi).\" Used to measure vast distances in space. - **Galaxies:** \"A galaxy is a huge system of stars, gas, and dust.\" Can be spiral, elliptical, or irregular. Our solar system is located in the Milky Way galaxy, a barred spiral galaxy. - **Big Bang Theory:** \"Scientists believe that our universe began as a small, dense, and hot point of matter and energy...This is called the big bang theory.\" The universe is still expanding and cooling. Evidence includes the observation that galaxies are moving away from each other. It is estimated to have occurred about 13.7 billion years ago.