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The Solar System Unit 4 Unit 4 Vocabulary 1. 2. 3. 4. 5. 6. 7. 8. 9. Rotation Revolution Axis of rotation Summer solstice Winter solstice Autumn equinox Vernal equinox Oblate sphere Geodesy Solar eclipse 11. Lunar eclipse 12. Ecliptic plane 13. Specific heat 14. Spring tide 15. Neap tide 16. Foucault’s pendulum 17. Coriolis effect 18. Latitude 10. Unit 4 vocabulary 19. Longitude 20. Conduction 21. Convection 22. Radiation 23. Big bang theory 24. Steady-state theory 25. Inflationary universe model 26. Doppler effect 27. Precession 28. 29. 30. Barycenter Nutation Eccentricity Chapters: ◦ 11.1 ◦ 28-31 The Sun-Earth-Moon System The relationships between the Sun, Moon, and Earth are important to us in many ways. – The Sun provides light and warmth and an energy source. – The Moon raises tides in our oceans and illuminates our sky with its monthly cycle of phases. – Both are used for the calendar and timekeeping systems. The Sun-Earth-Moon System Seasons, moon phases, tides and eclipses. • Our view of the Sun’s position changes throughout the year as Earth moves in its orbit about the Sun. Seasons occur on Earth because Earth’s axis is tilted. • The Moon goes through a cycle of phases each lunar month that correspond to our changing view from Earth of the sunlit side of the Moon. The Sun-Earth-Moon System Seasons, moon phases, tides and eclipses. Tides are caused by the gravitational attraction of the Moon, and to a lesser extent, the gravitational attraction of the Sun. A solar eclipse occurs when the Moon lies directly between Earth and the Sun. A lunar eclipse occurs when the Moon passes through Earth’s shadow. Moon Phases - Half the Moon is always lit by Sun - As the Moon orbits the Earth, we see different parts of the lighted half. http://www.nasm.si.edu/apollo30th/moontheater/phasepage2.html Revolution of Moon around Earth makes us have different angles of Moon Looks like it’s changing shape These are "phases" of the Moon http://btc.montana.edu/ceres/html/birthdayphases.htm “Waxing:” increasing, growing larger "Waning“: decreasing, growing smaller 9 Waxing: increase illuminated portion Waning: decrease illuminated portion Eight phases Daily Motions Earth’s Rotation – There are two relatively simple ways to demonstrate that Earth is rotating. 1. A Foucault pendulum, which has a long wire, a heavy weight, and will swing in a constant direction, appears from our point of view to shift its orientation. 2. Flowing air and water on Earth are diverted from a northsouth direction to an east-west direction as a result of Earth’s rotation in what is known as the Coriolis effect. Daily changes to Earth Due to rotation◦ Rotation – Earth spinning around its axis. ◦ Earth rotates towards the east (counter-clockwise from the north star) ◦ Causes the sun to rise, set and rise again in a 24 hour period. Daily changes to Earth Seasonal changes due to tilt and revolution ◦ Caused because Earth is tilted on its axis and moves around the sun ◦ Summer = the hemisphere tilted toward the sun ◦ Winter = the hemisphere tilted away from the sun Daily changes to Earth Tidal impact due to the moon and sun. ◦ High tide and low tides are caused by gravitational attraction with the moon (mostly) and the sun. Solar Eclipse The moon passes directly between the sun and Earth. Umbra area = total eclipse Penumbra area = partial eclipse Lunar Eclipse When the moon passes through Earth’s shadow. Can happen only at the time of a full moon and the moon is the opposite direction from the sun. Shape of the Earth Because Earth rotates, the sphere is distorted by the centrifugal force. This is the force that causes objects to move outward away from the center of gravity. Earth's circumference and diameter differ because its shape is classified as an oblate spheroid or ellipsoid, instead of a true sphere. Shape of the Earth The equatorial bulge at Earth's equator is measured at 26.5 miles (42.72 km) and is caused by the planet's rotation and gravity This means that instead of being of equal circumference in all areas, the poles are squished and a larger circumference and diameter at the equator. Shape of the Earth The Earth's gravitational pull is slightly weaker at the Equator due to its equatorial bulge. The slightly weaker gravitational pull and momentum of the spinning Earth makes equatorial regions ideal places for space launches. It takes an enormous amount of energy to launch a satellite or other spacecraft out of the Earth's atmosphere. Did you know that the Sun blasts more than a billion tons of matter out into space at millions of kilometers per hour? oUltimately, energy from the Sun is the driving force behind weather and climate, and life on earth. How does energy flow from the sun to the Earth? The transfer of energy from the Sun occurs primarily by radiation. Once the Sun’s energy reaches Earth, it is intercepted first by the atmosphere. A small part of the Sun’s energy is directly absorbed, particularly by certain gases such as ozone and water vapor. Some of the Sun’s energy is reflected back to space by clouds and Earth’s surface. How does energy flow from the sun to Earth? The Sun warms the planet, drives the hydrologic cycle, and makes life on Earth possible. The amount of sunlight received on Earth’s surface is affected by the reflectivity of the surface, the angle of the Sun, the output of the Sun, and the cyclic variations of the Earth’s orbit around the Sun. Specific Heat Why, on the same day, are the temperatures of water, sand, and asphalt so different? Specific heat is the key. Specific heat is how much heat energy is needed ro raise the temperature of a substance. Specific Heat Water has a very high specific heat. That means it needs to absorb a lot of energy before its temperature changes. Sand and asphalt, on the other hand, have lower specific heats. This means that their temperatures change more quickly. When the summer sun shines down on them, they quickly become hot. Transferring Heat Energy Here are three easy things to know about the way heat flows: 1) There has to be a temperature difference. Energy only flows as heat if there is a temperature difference. 2) Energy as heat flows from a higher temperature to a lower temperature. 3) The greater or larger the difference in temperature, the faster the energy flows. Radiation A type of energy that can travel through space. It doesn't need matter to conduct it from place to place. It can travel through air or through a vacuum. ◦ Ex: When you stand near hot molten lava, the heat you feel on your skin is mostly radiant heat. This type of heat doesn't need air to travel through. Even if you were standing in a vacuum (no air) you would feel the heat. Conduction A type of heat flow that results when things are actually touching. Energy traveling as heat by conduction needs matter to flow through. Conduction cannot travel through a vacuum because in a vacuum there are no atoms or molecules…something made of atoms or molecules has to touch something else made of atoms or molecules in order for there to be conduction. ◦ Ex: If you touch a hot object the heat is conducted by physical contact with your skin. Convection A type of heat transfer in which the motion is not generated by an external source but only by density differences. Can occur in fluid or air ◦ Ex: Ocean currents and winds Combustion and nuclear reactions Combustion: a chemical reaction (sharing, transfer, loss, gain of electrons; burning with the presence of oxygen. Nuclear reactions: ◦ Fission: Process in which heavy atomic nuclei split into smaller, lighter nuclei. ◦ Fusion: Process in which light hydrogen nuclei combine into heavier helium nuclei. The Sun emits many forms of electromagnetic radiation in varying quantities. As shown in the diagram: ◦ ◦ ◦ ◦ about 43% is in the visible parts of the spectrum about 49% in the near-infrared 7% ultraviolet less than 1 percent of solar radiation is emitted as xrays, gamma waves, and radio waves. Earth’s Magnetic Field The Earth has a substantial magnetic field. It protects us from harmful solar wind from the sun. Charged particles given off by the Sun are deflected by the Earth’s magnetic field. These particles interact with our atmosphere and create the auroras. Earth’s Magnetic Field The origin of the Earth's magnetic field is not completely understood, but is thought to be associated with electrical currents produced by the coupling of convective effects and rotation in the spinning liquid metallic outer core of iron and nickel. Earth’s Magnetic Field Solar wind is first deflected by the bow shock. The corresponding region of space sitting behind the bow shock and surrounding the Earth is termed the magnetosphere; it represents a region of space dominated by the Earth's magnetic field in the sense that it largely prevents the solar wind from entering. How our universe began There are three theories we will discuss about the origin of the universe: ◦ The steady state theory – says that new matter is created as the universe expands so that the overall density of the universe stays the same. ◦ The inflation theory –says that a period of extremely rapid expansion of the universe happened prior to the Big Bang and was dominated by a type of vacuum energy that later produced the matter that fills the universe today. ◦ The big bang theory – says that the universe began about 13.7 billions years ago as a single point and has been expanding ever since. Steady-state Theory Inflation Theory Big Bang Theory Organization of the universe Universe Galaxies Solar systems (planetary systems) Stars Satellite planets around a star – ex: Earth is a satellite planet to our sun The universe is expanding Astronomers in the early 20th Century got the shocks of their lives when they discovered that galaxies appeared to be rushing away from us. They did this by taking spectra of the galaxies, and then measuring the shift in their spectrum due to their motion. This phenomenon is called the Doppler Shift . With light, an object approaching you has its light waves compressed, or shortened. This is called a blue shift (since in visible light the shorter wavelengths are blue). If the object is moving away, the wavelengths are stretched, resulting in a red shift of the spectrum. The universe is expanding As objects move they emit a light ◦ Red shift- objects are moving away ◦ Blue shift- objects are moving closer ◦ All planets and galaxies are showing a red shift What does this mean? Movement through space Movement of our solar system through the Milky Way Galaxy. It takes the sun over 200 million years to revolve around the galaxy. The last time we were in the same place dinosaurs were just starting to appear. Motion of the Earth How does the Earth move within our solar system? ◦ Orbital motion – The Earth orbits (revolves) around the sun once per year. Change in seasons dependent on the tilt of the Earth ◦ Rotation around the axis – Earth rotates around the axis once per day. Causes day and night How does the solar system move in the galaxy? ◦ Our solar system follows the path of the sun around the galaxy center. Takes over 200 million years for our solar system to orbit the center of the Milky Way galaxy Motion of the Earth 1. Precession - A slight movement in the direction of the earth’s axis, but without any change in tilt. ◦ This changes the stars near (or not near) the Pole but does not affect the seasons as long as the angle stays the same. ◦ Happens over a period of 26,000 years. Right now our axis points at Polaris. In the year 14,000 it will point at Vega. Motion of the Earth 2. Nutation - a wobbling, or swaying motion around the axis ◦ Causes a change in the angle ½ degree over an 18 year period due to the moon exclusively ◦ Will slightly increase or decrease the amount of seasonal effects Motion of the Earth 3. Barycenter – the point between 2 objects where they balance each other. ◦ Our sun actually orbits the barycenter of the solar system as it moves through the galaxy because of the tug from the planets. Models of the solar system 2000 years ago, many philosophers developed ideas about the universe based on what they saw. One of these was Aristotle , a Greek philosopher who lived from 385 to 322 B.C. He promoted an Earth-centered (Geocentric) universe model. 49 7 Heliocentric Model Copernicus came up with the model we use today – the sun-centered or Heliocentric model. When Copernicus first developed his model it was quite controversial and was not accepted until after his death in 1543. Each planet revolved around the sun in the same direction but at different speeds. Both the geocentric and heliocentric models first had the planets orbits as perfect circles. Heliocentric Model Sun-centered model Heliocentric Model A Danish astronomer named Tycho Brache devoted his life to making detailed observations of the positions of the stars and planets. He hired a German assistant name Johannes Kepler. Kepler was able to explain Brache’s observation in mathematical terms. In the early 1600’s Kepler developed 3 laws that explained most aspects to planetary motion. 53 12 Kepler’s Laws Kepler’s 1st Law - law of ellipses Kepler’s 2nd Law - law of equal areas Kepler’s 3rd Law - law of periods 54 14 Kepler’s 1st Law, the law of ellipses Each planet orbits the sun in a path called an ellipse. ◦ An ellipse is an oval whose shape is determined by 2 points with the figure. ◦ Each of these points are called a foci. ◦ The sun is one foci point for our planets. ◦ Some ellipses look like circles - This happens when there 55is only one foci point. 15 Kepler’s 1st Law, the law of ellipses Because the planets do not travel in a perfect circle, they are not always the same distance from the sun. ◦ The point where the orbit is the closest is called perihelion. ◦ The point furthest away from the sun is called aphelion. Properties of Ellipses Eccentricity - how flattened the ellipse is, more flattened, the more eccentric (measurements always between 0 and 1 with 1 equaling a flat line and 0 equaling a perfect circle) 56 17 Kepler’s 2nd Law - law of Equal Areas Describes the speed at which any given planet will move while orbiting the sun. The speed at which any planet moves through space is constantly changing. A planet moves fastest when it is closest to the sun and slowest when it is furthest from the sun. 58 58 Kepler’s rd 3 Law - Law of periods Kepler found a mathematical relationship between the size of a planet’s ellipse and its orbital period. He found that the ratio of a planets ellipse to its orbital period is nearly the same for all of the planets The orbital period (p) in Earth years and distance from the sun (a) in A.U.’s gives the ratio of p²/a³=1 Mercury, the closest planet to the sun, takes 88 days to orbit the sun. While the dwarf planet Pluto requires 248 years to do the same. Fundamentals Sunlight reaching the Earth can heat the land, ocean, and atmosphere. Some of that sunlight is reflected back to space by the surface, clouds, or ice. Much of the sunlight that reaches Earth is absorbed and warms the planet. 2. When Earth emits the same amount of energy as it absorbs, its energy budget is in balance, and its average temperature remains stable. 3. The tilt of Earth’s axis relative to its orbit around the Sun results in predictable changes in the duration of daylight and the amount of sunlight received at any latitude throughout a year. These changes cause the annual cycle of seasons and associated temperature changes 1. Gradual changes in Earth’s rotation and orbit around the Sun change the intensity of sunlight received in our planet’s polar and equatorial regions. For at least the last 1 million years, these changes occurred in 100,000-year cycles that produced ice ages and the shorter warm periods between them. 5. A significant increase or decrease in the Sun’s energy output would cause Earth to warm or cool. Satellite measurements taken over the past 30 years show that the Sun’s energy output has changed only slightly and in both directions. These changes in the Sun’s energy are thought to be too small to be the cause of the recent warming observed on Earth 4. Test Review Draw and label the different moon phases What causes our seasons? Draw a lunar eclipse. Draw a solar eclipse. What is the penumbra? Umbra? Identify each season and which latitude the sun is directly over? What is the Foucault pendulum prove? And how does it prove it? What is rotation? How long does it take? What is revolution? How long does it take? What are 2 pieces of evidence that our Earth is rotating? Explain each. How many degrees is the Earth tilted? What causes the bulge around the equator? What is the shape of Earth? And why? Name, describe and give an example of the 3 ways heat is transferred on Earth. Explain differential heating of our Earth. (water vs. land) Why is Earth’s magnetic field important? Test Review Who came up with the Geocentric universe model? Who came up with the Heliocentric universe model? What do each of them mean? Know what all of Kepler’s laws state. What is Earth’s focus point? How is eccentricity measured? Do planets closer to the sun or further from the sun have faster revolutions? Know the organization of the universe. What is the evidence for the universe expanding? Know the definitions of precession, nutation and barycenter Be able to label – foci, major axis, semi-major axis, perihelion, aphelion