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Earth Science Unit 9: Our Place in the Universe Lessons 2 and 3: The Universe and Our Galaxy Make sure to have your study guide and a pencil and be ready to go when the timer dings! I pledge allegiance to the flag of the United States of America, and to the republic for which it stands, one nation under God, indivisible, with liberty and justice for all. *If you choose not to participate, turn volume down until we move to next slide. Student Expectations… Being part of this “school” is awesome! How can YOU make this ocean even more awesome??. = I will BE HERE! respond when my name is called, use polling tools , complete classwork, notes, and chat to participate! I will choose my attitude! I will demonstrate respect and follow directions for my classmates and teachers to help make their day! I will have fun learning! EVERYONE needs a working mic. Call 1-866-K12-care if it’s not working. Let’s get it fixed! What you can expect from class to understand the main features of the Big Bang Theory and to understand the theory of the origin of the solar system Essential question: How do scientists believe the universe was formed? K W L Expanding Universe Scientists believe that the universe is continuing to expand. They use what is called the Doppler Effect to determine the motion of massive groups of stars in space. Their observations of light show that bodies in the universe display a red shift, meaning they are moving away from us. The Doppler Effect One important observation scientists have made about the universe has to do with light. A wavelength is the distance between the crests of two waves. A special phenomenon called the Doppler effect explains how wavelengths of light— and sound—change when the source is in motion. The Doppler Effect: An Example Remember a time when you have been near a busy road and you hear the truck pass by. You may have noticed that the sound is high coming toward you and low going away. The sound’s wavelength changes because the source of the sound—the truck—is moving. Doppler Effect The Doppler effect works the same way with light. It explains how a star’s motion affects light coming from it. A star moving toward earth emits light in waves and when the star is closer, the waves shorten. On a spectrograph, shorter light waves appears bluer. A star moving away emits each wave farther, stretching them. Longer waves are redder. The shift's direction tells whether a star is moving toward or away from us. The shift's size tells us how fast it is moving. Quick Check! If a star is moving away from the earth, toward which color will its visible light be shifted? The Big Bang Theory Astronomers concluded that if the universe is expanding, it must have all been held together in one spot at some point. Scientists infer that the universe was once packed into a very small, dense space that burst apart in an enormous explosion called the "big bang." This is the big bang theory of the origin of the universe. The Big Bang Theory As with other scientific theories, evidence supports this idea. Besides the red shift of distant stars, there is evidence of cosmic background radiation. This glow, which can be observed all over space, is the leftover energy from the big bang. Working backwards, scientists determine that the big bang occurred about 14 billion years ago. What happened? Scientists have ideas about what happened in the very early period of our universe. • Early during the process, hydrogen formed and combined to make some helium. • Hydrogen and helium formed massive clouds from which large stars formed. • Other elements formed in large stars. Stars used up their early fuel, and some larger ones exploded. • These explosions formed large clouds of gas and dust. • From such clouds, a solar system with a star, planets, and other bodies of different sizes could form. Quick Check! According to the theory, what best describes the universe before the big bang? A. A star B. A planet C. A cloud of gas and dust D. A densely packed space Quick Check! Which of the following is used as evidence that the universe began with the big bang? A. Craters on the moon B. Leftover energy in the universe from the event C. The force of gravity D. The existence of atoms The Big Crunch?? Some scientists suggest that the expanding universe has a limit and that one day the universe will begin to contract. It may then produce a “big crunch,” forming another original point that will produce yet another big bang. For this to happen, there must be enough matter in the universe to create the gravitational force that pulls it back together. However, observations show that the universe is expanding at a fast-paced rate. Astronomers explain this puzzling observation with an idea about a new force, which they refer to as “dark energy.” Most of the universe appears to be made of dark matter and dark energy. 20 Light-Year There is a lot of space in space. Stars are very far apart. Distances in space are so large that it makes calculations using ordinary units of measurement, such as miles, impractical. As a result, scientists defined a unit of measure, called the light-year, to determine distances in space. A light-year is the distance light travels through space in one earth year. Light travels through space at a speed of 186,000 miles per second. Galaxies When you go outside on a clear night, you can see lots of stars. On a very clear night in a dark area, you may even be able to see a fuzzy white band that crosses the sky. This fuzzy band is our galaxy, the Milky Way. Galaxies are huge clusters of these stars, gas, and dust that are bound by the forces of gravity. Galaxies can contain billions of stars and are quite massive in size! For example, Andromeda, a nearby galaxy similar to the Milky Way, measures an astounding 1,290,000,000,000,000,000 (1,290 billion billion) miles across! Quick Check! Which number best describes the number of starts you would find in a galaxy? A. Hundreds B. Thousands C. Millions D. Billions The Shape of Galaxies There are billions of galaxies in the universe and each one is unique. Galaxies have different ages, sizes, and distances from earth. Astronomers classify galaxies by shape: spiral, elliptical, and irregular. Spiral Galaxies Spiral galaxies get their name for their arms of gas, dust, and stars that spiral out from a densely packed cluster of stars in the center. Spiral galaxies typically have a mix of stars, some young and some old. The Milky Way is a special type of spiral galaxy, called a barred spiral. Barred-spiral galaxies have a thick bar of stars and gas passing through their centers. From earth, the fuzzy white band that is the Milky Way doesn’t look like a spiral; it looks like a stripe. That is because we are looking at the Milky Way sideways, from inside one of its spiral arms. Elliptical and Irregular Galaxies The two other major kinds of galaxies are elliptical and irregular. An elliptical galaxy has a shape like a stretched circle, or oval. Elliptical galaxies usually have only old stars. This is because they contain little gas or dust. As their name suggests, irregular galaxies have no distinct or orderly shape. Many new stars are born in irregular galaxies. This is because these galaxies contain far more gas and dust than elliptical or spiral galaxies. Quick Check! What category of galaxy does not have a distinctive shape? A. Spiral B. Elliptical C. Barred Spiral D. Irregular Galaxy Clusters The universe contains billions— perhaps trillions—of galaxies. Quite often, galaxies are grouped together in what astronomers call galaxy clusters. A galaxy cluster may contain only a few galaxies or as many as thousands of galaxies. Galaxy clusters occur in bunches throughout space. This means that there may be hundreds of galaxy clusters in one region of space and almost none in another region of space. Spinning Galaxies Along with expanding, galaxies move in other ways, too. For example, spiral galaxies spin fast in the center, while their arms spin slower. Many scientists think that several, or perhaps most, galaxies rotate around the enormous gravitational pull of a massive black hole at their center. Interstellar Material The vast spaces between stars are not completely empty. In most galaxies, the space between stars contains dust and gases. These are called interstellar dust and gas (“inter” means between). Many scientists analyze dark matter that exists within galaxies and perhaps even between galaxies. Dark matter gets its name because it does not emit any radiation that we can observe on earth. No one knows for certain what dark matter really is or what it does, but scientists do know that dark matter is important in providing the gravitational force that holds each galaxy together. Quick Check! What is a light-year? A. The distance light travels in one earth year B. The distance light travels from the sun to the earth C. The distance light travels in one orbit of the mood D. The time it takes light to travel across the universe Fun Science Fact! All the individual stars that you can see when you look at the sky at night without a telescope belong to the Milky Way galaxy? The ancient Greeks most likely saw galaxies as milk-white wisps trailing over the night sky, which is why they probably named the Milky Way “Galaxies Kuklos” meaning the Milky Circle. Homework slide Exit ticket: Extension activity: