An introduction to modern astronomy's most important questions. The four sections of the course are Planets and Life in The Universe; The Life of Stars; Galaxies and Their Environments; The History of The Universe.

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From the course by University of Rochester

Confronting The Big Questions: Highlights of Modern Astronomy

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An introduction to modern astronomy's most important questions. The four sections of the course are Planets and Life in The Universe; The Life of Stars; Galaxies and Their Environments; The History of The Universe.

From the lesson

Are we alone in the Universe?

Planets and Life in The Universe - Exoplanets searches, exoplanet census, astrobiology

- Adam FrankProfessor

Physics and Astronomy

Okay, welcome back.

Â So when we deal with astronomy, when we

Â get started with astronomy, one of the most

Â difficult things is to deal with the enormous

Â size scales and time scales involved with astronomy.

Â It's really easy in astronomy just to have

Â everything be really, really big, and really, really old.

Â But that's really, not that helpful when we're trying to be specific

Â and trying to understand different evolutionary

Â processes that may operate on very

Â different, though very long, time scales.

Â So, for example, the age of the earth is 4.5 billion years, right?

Â and the dinosaurs were wiped out about 65 million years ago.

Â How do you hold those two numbers in your hand and make sense of them, right?

Â the way that scientists do this is through something

Â called scientific notation, that's how we deal with large numbers.

Â So the age

Â of the Earth is 4,500,000,000 years old, but that

Â gets written as 4.5 times ten to the nine years.

Â There's the first part of the number, the 4.5, which

Â tells you where you are in your order of magnitude.

Â But the important part is the order of magnitude, and that's the ten to the nine.

Â It's the exponent on the ten.

Â So we're talking about nine Powers of ten, essentially, for the age of the Earth.

Â Now all of that may have not made much

Â sense to you, so let's try and use something

Â that is familiar to all of us, in order

Â to understand the scientific notation, and let's use money, right.

Â Because we all understand the power of money, and we all know how much money

Â we have in our bank accounts and in our hand and what it feels like.

Â So what we're going to do is we're going to think about dollars.

Â We're goonna run through a set of examples thinking

Â about dollars and thinking about those dollars in terms

Â of order of magnitude.

Â So lets start off with lets say you have a dollar.

Â We all know what a dollar is.

Â And what can a $1 buy right?

Â Well basically these days a $1 will buy you a snickers bar.

Â Okay.

Â So $1 gets you a snickers bar and you know if you like snickers bars

Â that's great but your not going to be able to go much further than that.

Â So how about one order of magnitude more?

Â Let's jump up one order of magnitude, $10 and what will that buy you?

Â Well essentially $10 will get you a

Â you know,kind of bad compilation CD of 70s hits or a really great

Â one perhaps of Bob Marley depending on you know, which store you go to.

Â But that's what $10, when you jump one order of

Â magnitude, we go from a Snickers bar to a CD.

Â And what about the next order of magnitude?

Â That would be going up to 10 to the two, 10 raised to

Â the two power of dollars, $100, and what will it, that get you?

Â Well, that'll get you dinner at a nice restaurant, you know?

Â Not the fanciest

Â restaurant, but a pretty fancy restaurant, $100 should get you there.

Â So in two orders of magnitude, we've gone from a Snickers bar, which

Â isn't going to do much for you, to, you know, a nice restaurant.

Â Okay.

Â How about three orders of magnitude, $1000?

Â Well, $1000 will get you a plane ticket, you know, to some place nice.

Â Perhaps to, you know, a nice vacation, okay.

Â So $1000, three orders of magnitude takes us from

Â the Snickers bar to the ride on a jet plane.

Â One more order of order of magnitude, and that will take us up to a luxury car.

Â Now of course you're not going to be able to get a

Â luxury car for $10,000, but maybe for $60 or $70 or $80,000.

Â Again, this is what we mean by order of magnitude.

Â you might be able to at least, you know, get, get started on the luxury car.

Â Okay, so that is four orders of magnitude from the Snickers

Â bar to driving around in, you know, a nice Sports coupe.

Â How about five

Â orders of magnitude.

Â Well, five orders of magnitude will take you to you know, being able to get

Â that nice apartment perhaps that you could

Â use while you're driving around your sports coupe.

Â So, you know, $1000 got you a plane ticket to a nice place, could be Paris.

Â $10 to the 4, ten, tens of thousands of dollars gets you a sports coupe to drive

Â around in Paris and hundreds of thousands of

Â dollars will maybe get you an apartment in Paris.

Â Okay?

Â So just

Â five orders of magnitude, that's really what you have to think about.

Â Just five orders of magnitude took us from a Snickers

Â bar to a, an expensive apartment in a nice city.

Â Okay, and that is the important thing to see, is just five orders of magnitude

Â what the difference, the physical difference in our

Â experience would be, in having that much money.

Â Now in astronomy, we may easily jump up

Â 15, 20 orders of magnitude in both size and

Â time scale, in going from one kind of physical process to another.

Â So getting a handle on orders of magnitude would be a really

Â essential thing for being able to understand the rest of the class.

Â Okay.

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