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?
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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?
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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
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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
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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