1. Wednesday March 9 Thursday March 10 Unit QuestionWhat do we know about the universe? How do we know it? Guiding Question / Learning Target How big is the universe? Warm-upWhat are the steps to representative sampling? Agenda1.Scale of the Universe 2.Travel Times HomeworkQuiz Friday 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.

2. Solar System Size: How far away is the sun? 100,000 km One million km One billion km One trillion km 150 million km

3. If we shrunk our solar system, how far apart would everything be? If we shrunk our solar system, how far apart would everything be? http://www.youtube.com/watch?v=97Ob0xR0Ut8

4. 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

5. M er cu ry Ea rth Ve nu s M ar s

6. Ne pt un e Ur an us Sa tur n Ju pit er

7. Sirius 5 th farthest Light Year Alpha Centauri (nearest)

8. So how big are distances in the universe? Really, really BIG!

9. 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 distance 800 km/hourspeed Cross cancel your units, and do your math!

10. Calculating time: 6,900 km distance 800 km/hourspeed 6,900 800 hours 8.625 hours = 8 hours 37.5 minutes

11. So, how about to a real star?

12. We’re calculating the time to Sirius

13. First, how do astronomers measure distances to other stars? Light travels at a rate of speed = 300,000 km per second X ____________ seconds per minute = ___________________________________________ km per minute X ____________ minutes per hour = _____________________________________________ km per hour X ____________ hours per day = ________________________________________________ km per day X ____________ days per year = ________________________________________________ km per year THIS IS THE DISTANCE LIGHT TRAVELS IN ONE YEAR, OR ONE LIGHT YEAR 60 18,000,000 60 1,080,000,000 24 25,920,000,000 365 9,460,800,000,000 Trillion

14. The distance to the bright star Sirius is : 86,000,000,000,000 kilometers = 86 trillion kilometers = 8.6 x 10 13 kilometers One light year is 9,460,800,000,000 Km. We round it to 10,000,000,000,000 or 10 13 Km Sirius is 8.6 light years away That means we see Sirius as it was 8.6 years in the past

15. How is looking at Sirius seeing 8.6 years into its past?

16. 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.

17. 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.

18. 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!

19. 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 10 4

20. Scientific notation Walking 6.132 x 10 4 in one year (speed) Distance to Sirius= 8.6 x 10 13 km (distance) Find time! Time = distance/speed 8.6 x 10 13 6.132 x 10 4

21. 1.4 8.6 6.132 1.4 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 10 13 6.132 x 10 4 13 - 4 9 Exponents X 10 9

22. 1.4 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 10 13 6.132 x 10 4 1.4 8.4 6.132 13 - 4 9 Exponents X 10 9

23. How8.6 x 10 13 kilometers will it take? TransportationSpeedDistance/yearTravel to Sirius YEARS! Walking7 km/hr Bicycle25 km/hr Car105 km/hr Jet800 km/hr Space Shuttle28,000 km/hr Voyager56,000 km/hr 6.132 x 10 4 2.19 x 10 5 9.198 x 10 5 7.008 x 10 6 2.45 x 10 8 4.9056 x 10 8 1.76x10 5 176,000 3.51x10 5 351,000 1.23x10 7 12,300,000 9.34x10 7 93,400,000 3.93 x 10 8 393,000,000 1.4 x 10 9 1,400,000,000

24. Voyager 1977 Sept. 5 Voyager 1 launched from Kennedy Space Flight Center 2012 Aug. 25 Voyager 1 enters Interstellar Space (left the solar system)

25. 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