Lecture01.doc - But picture the difference between someone...

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Lecture 1 Introduction Astronomy is everywhere: It’s part of our language It’s part of out culture Automobiles – Saturn Hollywood – Orion Pictures Stars Products -- Comet Cleanser Quasar Televisions Pulsar Watches Astronomy tickles many people. Washington’s Air & Space Museum is the most heavily attended museum in the world. Why do we study astronomy We learn about our place in the cosmos We learn about how even the stuff that makes up our bodies and the world around us came into being. We learn about the nature of time and space Because it tickles our minds and our imagination Because it’s fun In astronomy we cannot measure things the way we do on earth. We can’t, for example, count every star in the Milky Way. We need to learn to estimate, and we need to learn how to learn how to do this in approximate ways. Powers of 10 Often , we will not need to know things very precisely, but to know them only to a power of 10.
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e.g. Difference in lifestyle between someone earning $20,000 and $25,000 per year is not that great.
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Unformatted text preview: But picture the difference between someone earning $10,000, $100,000, and $1,000,000 a year. The difference is huge. But we can write this as the difference between someone earning $10 4 , $10 5 , and $10 6 . This is a difference of only 2 powers of 10, but clearly a large difference in terms of wealth. The usefulness of understanding powers of 10 notation cannot be overstated. Picturing big numbers. The number of grains of sand in a one-gallon plastic jar is about a billion - 1 x 10 9 . How big is a billion? The number of seconds in a year is 3 x 10 7 , and multiplied by 33, you get about 1 x 10 9 . That is, if you are 30 years old you have lived about a billion seconds. If we think about how long a billion years is, then the ration of a year to a billion years is the same as the ratio of a second to about 30 years. The Universe is 13.7 billion years old. So, the ratio of a year to the age of the Universe is the same as the ratio of a second to 300 years....
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Lecture01.doc - But picture the difference between someone...

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