#### Transcript How big is the Universe

Wednesday March 9 Thursday March 10 Unit Question What do we know about the universe? How do we know it? Guiding How big is the universe? Question / Learning Target Warm-up What are the steps to representative sampling? 1. Place a grid over the picture 2. Count the number in a single box of the grid 3. Multiply that number by number of boxes in the grid. Agenda 1. Scale of the Universe 2. Travel Times Homework Quiz Friday Solar System Size: • How far away is the sun? • • • • 100,000 km One million km One billion km One trillion km 150 million km • If we shrunk our solar system, how far apart would everything be? • http://www.youtube.com/watch?v=97Ob0xR0Ut8 So… • If the Ball/Balloon (6” diameter) is the sun, how big is earth? • • • • Bouncy ball Marble Peppercorn Pin head • On a local map, let’s look at where things would be at scale M er cu ry Ea rth M ar s Ve nu s Sa tur n Ne pt un e Ur an us Ju pit er Light Year Sirius 5th farthest Alpha Centauri (nearest) So how big are distances in the universe? • Really, really Calculating time: • If we were to travel to our model alpha centauri by airplane, how long would it take us to reach it? 6,900 km 800 km/hour distance speed Cross cancel your units, and do your math! Calculating time: 6,900 km 800 km/hour distance speed 6,900 800 hours 8.625 hours = 8 hours 37.5 minutes So, how about to a real star? We’re calculating the time to Sirius First, how do astronomers measure distances to other stars? • Light travels at a rate of speed = 300,000 km per second 60 • X ____________ seconds per minute = 18,000,000 ___________________________________________ km per minute • X ____________ minutes per hour = 60 1,080,000,000 _____________________________________________ km per hour 24 • X ____________ hours per day = 25,920,000,000 ________________________________________________ km per day 365 • X ____________ days per year = 9,460,800,000,000 ________________________________________________ km per year • THIS IS THE DISTANCE LIGHT TRAVELS IN ONE YEAR, OR ONE LIGHT Trillion YEAR The distance to the bright star Sirius is : 86,000,000,000,000 kilometers = 86 trillion kilometers = 8.6 x 1013 kilometers One light year is 9,460,800,000,000 Km. We round it to 10,000,000,000,000 or 1013 Km Sirius is 8.6 light years away That means we see Sirius as it was 8.6 years in the past How is looking at Sirius seeing 8.6 years into its past? Looking into the Past • Alpha Centauri is 4.3 light years away • When we look at Alpha Centauri, how far into the past are we looking? • 4.3 years! The light takes that long to reach us. So it is 4.3 years old by the time we see it. Stellar Distance and History • You will have 15 minutes to work on this. • We will compare important events in the world’s history to cosmic bodies. We are going to calculate how long it would take to travel to Sirius Two ways to do math • Do the math straight away, with all those 0’s • Use your scientific notation! Scientific notation • • • • • • Calculate the distance you can walk in 1 year. Hours in a year? 24 hr/day *365 days/year = 8,760 hr/year 7Km/hr*8760 hr/year= 61,320 km/year Convert that to scientific notation! • (remember only one number to the left of the decimal! Each place you move is one more for the exponent!) • 61320 • Moved 4 places = • 6.132 x 104 Scientific notation • Walking 6.132 x 104 in one year (speed) • Distance to Sirius= 8.6 x 1013km (distance) • Find time! • Time = distance/speed 8.6 x 1013 6.132 x 104 Dividing exponents • Divide the non-exponent numbers as usual. • Since the base number is the same (10), you just subtract the exponents. • Recombine 8.6 x 1013 6.132 x 104 8.6 6.132 X 10 1.4 13 - 4 9 Exponents Dividing exponents • Divide the non-exponent numbers as usual. • Since the base number is the same (10), you just subtract the exponents. • Recombine 8.2 x 1013 6.132 x 104 8.4 6.132 1.4 X 10 1.4 9 13 - 4 9 Exponents 13 How8.6 x 10 kilometers will it take? Transportation Speed Distance/year Walking 7 km/hr Bicycle 25 km/hr 2.19 x 105 3.93 x 108 393,000,000 Car 105 km/hr 9.198 x 105 9.34x107 93,400,000 Jet 800 km/hr Space Shuttle 28,000 km/hr Voyager 56,000 km/hr 6.132 x 104 7.008 x 106 2.45 x 108 4.9056 x 108 Travel to Sirius YEARS! 1.4 x 109 1,400,000,000 1.23x107 12,300,000 3.51x105 351,000 1.76x105 176,000 Voyager • 1977 Sept. 5 Voyager 1 launched from Kennedy Space Flight Center • 2012 Aug. 25 Voyager 1 enters Interstellar Space (left the solar system) Your turn • • • • • Finish the questions on Calculating Stellar Travel Times Finish Stellar Distances and History We’ll discuss in class on Friday Homework if not done by end of today! Finish Hubble Before Friday also