Chapter 2: Earth in Space 1. Old Ideas, New Ideas 2. Origin of the Universe 3. Stars and Planets 4. Our Solar System 5. Earth, the Sun, and the Seasons 6. The Unique Composition of Earth Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Earth in Space Concept Survey Explain how we are influenced by Earth’s position in space on a daily basis. The Good Earth, Chapter 2: Earth in Space Old Ideas, New Ideas • Why is Earth the only planet known to support life? • How have our views of Earth’s position in space changed over time? • Why is it warmer in summer and colder in winter? (or, How does Earth’s position relative to the sun control the “Earthrise” taken by astronauts aboard Apollo 8, December 1968 climate?) The Good Earth, Chapter 2: Earth in Space Old Ideas, New Ideas From a Geocentric to Heliocentric System sun • Geocentric orbit hypothesis - Ancient civilizations interpreted rising of sun in east and setting in west to indicate the sun (and other planets) revolved around Earth Earth pictured at the center of a – Remained dominant geocentric planetary system idea for more than 2,000 years The Good Earth, Chapter 2: Earth in Space Old Ideas, New Ideas From a Geocentric to Heliocentric System • Heliocentric orbit hypothesis –16th century idea suggested by Copernicus • Confirmed by Galileo’s early 17th century observations of the phases of Venus – Changes in the size and shape of Venus as observed from Earth The Good Earth, Chapter 2: Earth in Space Old Ideas, New Ideas From a Geocentric to Heliocentric System • Galileo used early telescopes to observe changes in the size and shape of Venus as it revolved around the sun The Good Earth, Chapter 2: Earth in Space Earth in Space Conceptest The moon has what type of orbit? A. Geocentric B. Heliocentric C. Neither The Good Earth, Chapter 2: Earth in Space Go back to the Table of Contents Go to the next section: Origin of the Universe The Good Earth, Chapter 2: Earth in Space Earth in Space Conceptest List these cosmic features in order of size, beginning with the largest: A. universe, galaxy, star, planet B. star, galaxy, universe, planet C. universe, planet, star, galaxy D. galaxy, universe, star, planet The Good Earth, Chapter 2: Earth in Space Origin of the Universe Earth, a small, rocky planet, orbits the . the sun, a medium sized star, . one of billions of stars in the Milky Way galaxy, . one of billions of galaxies in the universe. The Good Earth, Chapter 2: Earth in Space Origin of the Universe Size of the Universe: Luminosity Brightness of pulsating stars – cepheid variables – was used to determine distance from Earth – Brighter stars = closer to Earth – Dimmer stars = farther from Earth Repeated measurements determined cepheid variables were moving away from Earth – Interpretation Æ the universe is expanding The Good Earth, Chapter 2: Earth in Space Origin of the Universe Size of the Universe: Doppler Effect Doppler Effect: The apparent change in the frequency of sound waves or light waves due to the motion of a source relative to an observer – Example: change in frequency (pitch) of a siren from passing police car The Good Earth, Chapter 2: Earth in Space Origin of the Universe Doppler Effect Example: The change in frequency (pitch) of a siren from passing police car No change in Higher frequency Lower frequency frequency for sound when sound waves when sound waves waves when police are compressed for are stretched out for siren and observer objects moving objects moving away are stationary toward an observer from an observer The Good Earth, Chapter 2: Earth in Space Origin of the Universe Size of the Universe: Doppler Effect Doppler Effect: The apparent change in the frequency of sound waves or light waves due to the motion of a source relative to an observer – Sound/light waves are compressed for objects moving toward an observer – Sound/light waves are stretched out for objects moving away from an observer • The change in frequency of a passing siren can be used to determine the speed of the police car The Good Earth, Chapter 2: Earth in Space Origin of the Universe Size of the Universe: Doppler Effect Light on Earth is a form of solar radiation and occurs at specific wavelengths from 380-750 nanometers • The color of light from distant stars is stretched (“shifted”) toward wavelengths at the red end of the spectrum Shorter wavelength Longer wavelength The Good Earth, Chapter 2: Earth in Space Origin of the Universe Size of the Universe: Doppler Effect Astronomers use the degree of “red shift”to determine the distance to far away galaxies • more than 13 billion light years (distance) from Earth The Good Earth, Chapter 2: Earth in Space Origin of the Universe Size and Age of the Universe • If the color of light from other stars is “shifted” toward the red end of the spectrum – Other objects in the universe are moving away from Earth and from each other – The farther away the star, the greater the red shift and the faster the star is moving away from us – The universe must be expanding – Light from the most distant stars has traveled more than 13 billion light years (distance) in 13 billion years (time) The Good Earth, Chapter 2: Earth in Space Earth in Space Conceptest What is the Doppler Effect as used in exploration of the universe? A. A change in the speed of light as the source moves relative to the observer B. A change in luminosity of light as the source moves relative to the observer C.A change in the frequency of light as the source moves relative to the observer The Good Earth, Chapter 2: Earth in Space Earth in Space Conceptest Suppose the light spectrum from a distant star shifted toward the blue end of the light spectrum. What would this imply? A. The star is moving away from us B. The star is moving toward us C. The star is not moving relative to us The Good Earth, Chapter 2: Earth in Space Earth in Space Conceptest Suppose you and a friend are tossing a ball back and forth. The ball has a speaker that lets off a constant noise. How does the frequency of the noise you hear vary from when you throw the ball to when you catch the ball? A. The frequency increases B. The frequency decreases C. The frequency does not change The Good Earth, Chapter 2: Earth in Space Origin of the Universe The Big Bang Theory • Reversing the expansion of the universe suggests the universe began with an episode of rapid expansion from a much more compact form • The almost instantaneous period of rapid expansion is known as the Big Bang • Within hours of the Big Bang, simple elements (hydrogen, helium) formed as subatomic particles combined − Hydrogen – 1 proton + 1 electron − Helium – 2 protons + 2 neutrons + 2 electrons The Good Earth, Chapter 2: Earth in Space Earth in Space Concept Survey Scientists often suggest that the expansion of the Universe is similar to the expansion of raisin bread as it bakes in an oven. The loaf increases in size and individual raisins move farther apart in the expanding bread. During a homework assignment, two students suggest two more analogies (see below) for the universe. These answers are not considered as good as the raisin bread analogy. Why? a) The universe expands similarly to the concentric ripples formed when a rock is thrown into a pond. b) The universe is similar to a Jell-O mold enclosing pieces of fruit (galaxies). The Good Earth, Chapter 2: Earth in Space Go back to the Table of Contents Go to the next section: Stars and Planets The Good Earth, Chapter 2: Earth in Space Stars and Planets • Just 3 elements – hydrogen, oxygen, carbon - make up 90% of the human body (by weight) – Five more – nitrogen, calcium, phosphorus, potassium, sulfur – make up 9% more – Small amounts of many other elements needed for life • Hydrogen formed soon after the Big Bang • Other elements and complex compounds formed during the life cycle of stars The Good Earth, Chapter 2: Earth in Space Stars and Planets • Gravity pulled together irregular clouds of gas and dust generated from the Big Bang to form galaxies (systems of stars) Stars and galaxies in a small section of the universe. Image taken by Hubble space telescope The Good Earth, Chapter 2: Earth in Space Stars and Planets • Gas and dust material clumped together to form millions of stars (ongoing process) − Very high temperatures and pressures in the interiors of stars fuses hydrogen atoms together – nuclear fusion – to form helium − Stars burn out when hydrogen is used up False color image from NASA Spitzer Space telescope showing cool gas and dust that are incubators for new stars. The Good Earth, Chapter 2: Earth in Space Stars and Planets • Stars vary in size, age − Giant stars are 100- 1,000 times brighter than the sun but burn out faster − Giant stars burn out in 10-20 million years − Intermediate-sized stars such as the sun will last approximately 10 billion years Life cycle stages and types of stars (Hertsprung-Russell diagram). The Good Earth, Chapter 2: Earth in Space Stars and Planets • The sun will collapse when hydrogen is used up − resulting in a temporary temperature rise and expansion (to form a red giant star) − higher temperatures would fuel more fusion converting helium Æ carbon • Fusion would end when helium is used up • The loss of the heat of fusion would form a smaller white dwarf star that will cool to a black dwarf star The Good Earth, Chapter 2: Earth in Space Stars and Planets • Giant stars collapse over multiple stages, initially forming red supergiant stars − Collapse forms increasingly complex elements (e.g., carbon Æ oxygen) • Final stage is a massive explosion – supernova – that fuses heavier elements together and blasts them Kepler’s supernova.