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WHERE IN THE UNIVERSE ARE WE??? The Heliocentric Model • From 5,000 ago until the 1500s, a geocentric view of planetary motion was widely accepted • Polish astronomer Nicolas Copernicus developed the first heliocentric model in which the planets orbit the sun in circles Problems with the Geocentric Model • Assumed that planets and stars orbited a stationary Earth • Could not explain the apparent retrograde motion of some planets (Mars) • Retrograde motion= planets further from the sun move slower in their orbit due to less gravitational pull and appear to move backwards From Circles to Ellipses • Danish astronomer Tycho Brahe studied the movement of Mars taking nightly measurements WITHOUT a telescope • Accurately measured the elliptical orbit within a matter of degrees • Died in 1602, seven years before the telescope was invented Brahe’s Apprentice • Johannes Kepler (Brahe’s apprentice) was in the right place at the right time and used Brahe’s data to proposed the first of a set of three laws that are named after him Kepler’s Laws 1. The planets move around the sun in ellipses 2. The imaginary lines connecting the sun to each planet sweeps equal areas in equal time 3. The relationship between a planet’s ellipse and its orbital period is: P2 = a3 (where P equals the orbital period and a equals the length of the semi-major axis) Eccentricity • Due to its elliptical orbit, a planet is not at a constant distance from the Sun • Perihelion = closest to • Aphelion = farthest from Kepler’s Second Law Kepler’s Third Law • The farther a satellite is from the object it is revolving aroung: 1. The longer it will take to complete an orbit 2. The greater the distance it will travel to complete the orbit 3. The slower its average speed of motion Newton’s Laws (physical science review!) 1. An object in motion tends to stay in motion UNLESS an outside forces acts upon it 2. An object accelerates in the same direction of the force applied 3. For every action, there is a equal and opposite reaction Kepler + Newton •Gravity pushes planets towards the sun •The gravitational force holding the planets on their orbit is continuously changing the planets’ velocity creating elliptical orbits •When planets are closer to the sun, they speed up! Why does the night sky change? Parallax • An apparent change in the direction of an object, caused by a change in observational position that provides a new line of sight. Precession • Earth’s wobble on its tilted axis • It takes the Earth about 26,000 years to wobble • It is caused by a tug of war on Earth by the Sun and Moon, but the Moon’s pull is stronger due to proximity END OF MOTION IN SPACE NOTES DAY 1! Parts of the Universe • Use the chart and sticky labels provided to organize the terms on the right. • When you think you have the hierarchy, raise your hand to be checked! • • • • • • • • • • • • • Andromeda Moons Nebula Milky Way Big Bang Galaxy Local Cluster Solar system Planets Sun Star Universe Telescope Where did our solar system come from? • Stars and planets form from interstellar clouds (nebulae) of gas and dust, mostly made up of hydrogen and helium • We can see these all over the Milky Way galaxy • Clouds begin to condense when gravitational pull of the matter in these clouds grows stronger • This is likely how our solar system came to be Where did our solar system come from? Where did our solar system come from? • Tiny condensed particles of matter from within the interstellar cloud that started it all began to clump and bind a few billion years ago • As the diameters of these objects grew, they became planetesimals • As growth continued, some planetismals were destroyed through meter collisions, but some survived—and became the eight planets of our solar system • The third planetismal from the Sun became our Earth Where did our solar system come from? • Scientists theorize that the first planet to form in our solar system was Jupiter, a gas giant and the fifth planet from the Sun • Jupiter kept growing larger and pulling remaining dust and debris from space into its orbit, as did the other gas giants Where did our solar system come from? • This is likely why the interior planets (including us) remained small and rocky and (initially) without any satellites (moons) • Some debris didn’t get pulled into a planetary orbit and today makes up what is commonly known as an asteroid belt (between Mars and Jupiter) What happened to the “extra” matter? • Some matter did not get pulled into a planetary orbit during the formation of our solar system • Meteor= “space trash” burnt up by our mesosphere (shooting star, satellite) • Meteorite=“space trash” that comes in contact with Earth’s surface What happened to the “extra” matter? • Comets= small, icy bodies with highly eccentric orbits around the Sun • Periodic comets= repeatedly orbit in the inner solar system – Ex: Halley comet, last seen in 1986, expected again in 2061 (~75 year period) What is a Galaxy? • Galaxy: Cluster or bunch of billions stars. There are about 100 billion galaxies in the universe. • Our neighboring galaxy, Andromeda, is 2.5 million light years from Earth! • We belong to the local group, a cluster of about 35 galaxies. What is a Galaxy? What does the Milky Way look like? What does the Milky Way look like? Sagittarius A, 100 billion+ late main sequence and Red Giant stars make up the disk, suggesting that this is the oldest part of the galaxy the mass in the center of our galaxy is about 2.6 million times the mass of the sun and it believed to be a super-massive black hole that “glows” because of the hot gas spiraling into it The youngest stars in the galaxy make up the spiral arms, this is where most star Edwin Hubble • Born in small-town Missouri in 1889 • Attended high school in Chicago, excelling at academics and athletics (broke state high jump record, Varsity basketball player and boxer) • Attended college on scholarship, continuing to play sports and earned two degrees in mathematics and astronomy • Went to Oxford University Law School on a Rhodes scholarship, where he did not continue his studies in astronomy, but instead studied law. • He quickly realized that he wasn’t satisfied practicing law and went back to school for his astronomy doctorate Edwin Hubble • As soon as he finished up his third degree, he was drafted during WWI and didn’t begin his career as an astronomer in California until 1917 • First person to… – See other galaxies – Develop a system to classify galaxies – Explain redshifft – Define the Big Bang Theory • Hubble also refined Einstein’s theory of relativity and the two famous scientists got together in 1931 because Einstein was grateful for Hubble correcting his mistakes How do we know the universe is expanding? • Edwin Hubble discovered that most galaxies have redshift in their spectra • Redshift of an object in space depends on distance from Earth • The farther away an object is, the faster it is moving away How does the night sky tell us about the past? • Because many galaxies are so distant, it takes a long time for their light to reach Earth • Ex: When we see sunlight, we are really seeing light the Sun produced eight minutes before Models of the Universe • Steady State Theory • Big Bang Theory (Fred Hoyle): New (Edwin Hubble): matter has been The universe began created such that as a point and has when objects in been expanding space move, new ever since objects fill that void • NOT really an • Conflicts with the explosion, but an law of conservation expansion of matter Big Bang v. Steady State Which theory is right? • BOTH theories have observational tests to support them • BUT evidence weighs in favor of the Big Bang • If the universe began as a highly compressed point (as stated by Big Bang), then high temperature and pressure would have created a great deal of high energy radiation • In 1965, scientists discovered persistent background noise in radio antenna caused by weak radiation • This is believed to be remnant of the Big Bang, as the energy has shifted over time • Steady State supporters have no explanation of this What is going to happen to our universe? 1) Closed Universe (Big Crunch)— expansion will stop and shift to contraction 2) Open Universe—expansion will continue forever 3) Flat Universe (Big Chill)—expansion will slow to a halt in an infinite amount of time, but never contract What is going to happen to our universe? What is going to happen to our universe? • The constant interaction between gravity (pressure in) and expansion (pressure out) will determine what happens • One approach to determining the fate of the universe is to measure how much expansion has already slowed, using redshift of distant galaxies • Latest evidence: expansion has started to speed up again! We don’t know what’s causing it!! • Most evidence points to a flat universe (inflationary model) END OF DAY 2 NOTES!! Big Bang Balloon Quick Lab • Use a felt-tip pen/marker to make 5 dots in a row, 1 cm apart, on your balloon Label one “Earth” and the others A-D (these represent other galaxies) • Partially inflate the balloon (1-2 big breaths) and hold it…do not tie it! Use a piece of yarn to measure the distances at time 1, convert to centimeters using your ruler, and record • Repeat for time 2 and 3, then answer analysis questions Set up a table like this… POINT A B C D Distance 1 Distance 2 Distance 3 Distance 4 Hubble’s Law • Blow up your balloon just a little (don’t tie it!). Now measure the distance from Earth to each dot again • Inflate the balloon a little more and repeat measurements. • Now fully inflate the balloon and tie it. Complete your final measurements. Analyze & Conclude Questions 1) Are the dots still separated from each other by equal distances? • Which dot moved the greatest distance? The least distance? • How would your results change if you had measured distances from dot D instead? • Which of the three proposed models of universal expansion would be best modeled by your balloon? Explain. Our Motion & the Moon Nutation Barycenter What makes our Moon weird? • Large in comparison to the planet that it orbits –27% the radius of Earth • Great distance from Earth (most moons are closer) • Solid rocky composition (most are icy) Moon Vs. Earth Differences • The moon can get reallllllly hot and cold (127°C, -173°C), but because it has no atmosphere, it does not retain heat in the absence of sunlight • No erosion (no wind or water) Similarities • Areas of high elevation (highlands) and low elevations (maria and craters) • Very similar mineral content How was the Moon formed? • Capture Theory: As the solar system was forming, an object came too close to the forming Earth and got sucked into our gravitational pull • Simultaneous Formation Theory: The moon and Earth formed at the same time and in the same area (that’s why the compositions are similar) • Impact Theory: The moon formed as a result of the collision of Earth and a Mars-sized object about 4.5 billion years ago. Debris from both merged together to form the moon (most widely accepted!) Moon Phases: Oreo Lab 1. Separate your cookies carefully, so that ½ of the cookie has ALL of the frosting and the other ½ of the cookie has NO frosting. 2. Use your plastic butter knife to scrape off the frosting from the first cookie, making a shape of the waxing crescent. 3. You will continue using the butter knife to scrape off the frosting for each of the moon phases. (How will you represent new moon?) 4. Place the cookies in order on a paper plate and LABEL them correctly. Use chocolate frosting as “glue”. 5. Don’t forget to add Earth to your model! As, you finish, you should begin work on Study Guide 28.3 (p. 180-182) The difference between… Rotation • Spinning of the earth around it’s axis • Period: 24 hours • Creates day and night and time differences Revolution • Movement of the earth around the sun • Period: 1 year • In the elliptical orbit, sometimes different parts of the planet are closer to/farther from the sun • Gives us seasons Earth is tilted! What is a solstice? SUMMER SOLSTICE • Sun is directly over the Tropic of Cancer at 23.5° N • The Northern hemisphere has its longest days • The Southern hemisphere has its shortest days WINTER SOLSTICE • Sun is directly over the Tropic of Capricorn at 23.5° S • The Southern hemisphere has its longest days • The Northern hemisphere has its shortest days What is an equinox? • Equi = equal Nox = night • Happens twice a year in the autumn and spring • The lengths of the day and night for both hemispheres is the same Earth’s Tilt and Climate Change • The Earth wobbles in space so that it’s tilt changes about 25 degrees…every 41,000 years • Change in tilt = Change in intensity of seasons • When spring/summer is milder, ice and snow don’t melt • When there is more ice and snow on the earth, it reflects sunlight instead of absorbing it and it gets even colder • Carbon dioxide levels fall as ice sheets grow • The last ice age was about 10,000 years ago