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SpeakerWhat unit of measure would you use to describe the distance from Washington,
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SpeakerDC to Los Angeles, CA?
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SpeakerWould you use miles, inches,
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Speakerkilometers, or meters?
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SpeakerWhat about your height? Would you measure it in inches or feet?
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SpeakerAnd how about the width of your classroom?
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SpeakerDo you use kilometers, meters,
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Speakeror feet? You can choose any unit of measure you wish,
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Speakeras long as it's convenient for everyone to understand.
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SpeakerWhen describing distances at the scale of the solar system,
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Speakereven units like miles and kilometers lead to numbers that are in the millions or the billions,
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Speakerand that makes it very hard to understand them.
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SpeakerFor example, the distance between the Earth and the Sun is about 149,000,000 kilometers.
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SpeakerBetween the Sun and Pluto, the distance is about 5.9 billion kilometers.
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SpeakerBut suppose we wanted to compare these two numbers.
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SpeakerIt's not easy to see that Pluto is about 40 times as far from the Sun as Earth is.
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SpeakerIt would make sense to use a smaller scale in order to get a better idea of the distances between the planets.
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SpeakerTo come up with that scale, we have to define a baseline.
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SpeakerThe baseline that astronomers use is the distance between the Earth and the Sun.
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SpeakerThis distance is known as the Astronomical unit.
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SpeakerThe Astronomical unit or AU represents the distance between the Earth and the Sun,
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Speakerwhich is about 93,000,000 miles.
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SpeakerThe astronomical unit is the baseline that astronomers use to determine the distances to the planets in our solar system and to the stars beyond.
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SpeakerSo, let's have a look at the scale of the solar system,
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Speakerwhere one astronomical unit equals 93,000,000 miles.
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SpeakerBased on the astronomical unit,
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Speakerit's easy to compare the distances between all the other objects in the solar system.
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SpeakerWe can solve the Mars distance problem using a proportion.
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SpeakerThe first ratio is the scale and the second ratio is the distance of Mars to the Sun,
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Speakerand miles represents the distance from Mars to the Sun.
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SpeakerAfter setting these ratios equal to each other,
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Speakerlet's find the cross products. The equation becomes 1 * n = 93 million * 1.52.
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SpeakerMultiplying, we get the distance from Mars to the Sun to be approximately 141 million miles.
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SpeakerUsing the astronomical unit instead of the mile or the kilometer makes it easier to compare the distances between the planets and the sun.
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SpeakerFor example, it's easier to remember that Mars is 1 1/2 times further away from the sun and the Earth than it is to remember that it's 48 million miles farther away from the Sun than the Earth.
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SpeakerThe Voyager spacecraft is 8 billion miles,
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Speakeror 13 billion kilometers,
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Speakerfrom the Earth. It's at the far edge of our solar system,
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Speakerready to head out into interstellar space.
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SpeakerBased on what you've learned about scaling and the astronomical unit,
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Speakercan you estimate the distance of Voyager One from the Earth in astronomical units?
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SpeakerWorking with a partner, take a few minutes and see if you can solve this problem.
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SpeakerVoyager One is over 8 billion miles away from Earth.
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SpeakerEstimate how far in astronomical units Voyager One is from the Earth.
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SpeakerRemember, the scale is 1 astronomical unit equals 93,000,000 miles.
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SpeakerOK, So what did you come up with?
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SpeakerIf you said that Voyager was 86 astronomical units away from the Earth,
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Speakeryou're correct. Do you have a sense for how far that is?
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SpeakerSuppose that Voyager one were stationary and you were able to ride in a car traveling at 55 mph to get to it.
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SpeakerThe trip would take you over 16,000 years just to reach the satellite.
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SpeakerThat would be quite a lengthy and expensive vacation.