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We’re gonna continue our discussion today of the scientific method and we’re gonna be finishing up Chapter 1, and then we’ll begin Chapter 2 which is more or less the history of astronomy. So we’ll be doing both of those today. I wanted to start out today discussing how we number things in astronomy. We usually talk about powers of 10. And the reason is that astronomy has so many large numbers and, as you’ll find out when we go through the semester, many small numbers that we have to have an easier way of writing them than just writing them out all the way along. It’s easy if you’re writing the word one or ten. When you start writing words like ten thousand, five hundred and twelve it’s a long set of words. And so you prefer to use numbers. If you’re using numbers and you start talking about millions or billions, even the numbers get extremely long. And so we like to have a shorthand that helps us to write those very large numbers without spending five minutes putting zeroes in. And so we talk about powers of 10 where 1 is 10 to the 0, 10 is 10 to the 1, 100 is 10 squared or 10 to the 2, 1000 is 10 to the 3 or 10 cubed. Now, up to that point it’s just as easy to write the 100 out or the 1000 out as it is to put 10 to the cubed or 10 squared. But once you get larger than 1000 -- when you get up to 10,000 it’s 10 to the 4. Those are only three digits: 1, 0, and a 4. Whereas if you had to write out the 10,000, you have a 1 plus 4 zeroes. And so once you get past 10,000 it’s better to use these powers of 10 because it’s easier to write. So you have 10 to the 5th, which is hundred thousand; 10 to the 6th, which is a million; 10 to the 7 which is 10 million; 10 to the 8 which is 100 million; 10 to the 9 which is a billion. And we keep going: 10 to the 10, 10 billion; 10 to the 11, 100 billion; 10 to the 12, a trillion. These are pretty big numbers. Beginning to sound like the national debt. You
can even go up to 10 trillion, 10 to the 13; or 100 trillion, 10 to the 14. I could keep going. We can go up to 10 to the 15 which is a quadrillion. But we don’t usually bother with those. So keep in mind that you can write the number very easily, even if it’s an extremely large number like a billion. If you had to write a billion out, notice that you’ll have 9 zeroes after the 1. You’ve gotta start counting them. There’s so many zeroes you have to count ‘em to make sure they’re all there. Or a trillion. You’ve got 12 zeroes after the 1. Whereas writing a trillion is quite easy as 10 to the 12. So we will use those powers of 10 when we’re discussing large numbers in astronomy. Keep in mind that the very words that are used to describe large numbers are that they’re astronomical — because they’re very large. And so we will be discussing numbers in billions, sometimes in trillions, quite often in millions. And so you’ll be seeing 10 to the 6 as a million, 10 to the 9 as a billion, 10 to the 12 as a trillion. If you can remember those three, you can fill in the rest of it. Now, we’re usually going to be using the metric system in here. We’re going to be discussing meters and kilometers. It’s not going to be inches or feet or miles. Although sometimes I’ll probably mention those units because they’re more familiar to you, but I’ll always try to mention also the metric unit so that you get familiar with that. There are lots of prefixes that go with those large numbers. And so if you’re looking at these numbers, 10 to the 15th^ I mentioned was a quadrillion. Well, if you’re trying to describe that, you would use the term peta. If you’re talking about trillions, 10 to the 12, you would say tera. Now, some of those numbers you’ve probably never heard that prefix. But I’m now hearing discussions of tera-bites of data being stored by
of having those new positions.” Then Copernicus proposed that the planets go around the sun. He had a hypothesis. He didn’t actually prove it or come up with a detailed theory, although he did fill lin his hypothesis enough that he actually built a model. But then Johannes Kepler described the planet orbits using that model and pretty well set the stage for Isaac Newton to come along with his theory of gravitation and motion. And by combining the observations of Tycho Brahe, the hypothesis of Copernicus, the model of Johannes Kepler filling in Copernicus’s ideas, we came up with the theory of the motions of all the objects in the solar system. Notice that once you’ve got a theory, you can then predict what’s going to happen. You can go on and predict how the planets should move. If the predictions had failed — and they didn’t; but if they had failed, you see that there’s a loop back here, back to hypothesis. If your predictions fail when you’ve gone through all of this work, then you have to start with a new hypothesis. A new idea as to what’s going on in order to figure out how those planets move. But if you test it and you get a correct prediction, then you have more observations which then back up your hypothesis. So any time you have a theory and you test it, you make predictions, you compare your predictions with the reality. If the test passes — which you always hope it does if you’ve worked on the theory for a long time — then you have additional evidence in favor of your theory. But if for some reason the test fails, you have to throw the theory out. You have to get a new hypothesis, build a new model, come up with a new theory. So new theory is completely perfect. It may be extremely good. Every test has passed. But there’s always that possibility that at some point somebody will make a test, a valid test, and will discover that there’s a problem with the theory.
Sometimes you can just tweak the theory. If the theory is fairly complicated, maybe you’ve got one part of it a little bit wrong. So you adjust that part and then everything else works fine. But sometimes you look at the theory and there’s a big problem. The predictions are not working. You can’t just keep using the theory and ignore the predictions. You have to come up with a new theory or a modified theory at least. Any question on that? I hope by now you understand what the scientific method is. It’s seeing what’s going on, coming up with an idea of how to explain it, building a model of how it all works, filling in the details until you have a theory, and then using that theory to make predictions to test your theory. At the end of the chapter the author discusses other systems of knowledge. These are not science. For example, the author discusses the appeal to authority. Because so-and-so said it’s correct, it must be right. Well, that may go a certain way. You may have somebody you think really knows what’s going on and so that person said, “This is the way it is.” But that’s not science. That’s just an appeal to authority. That would be like my saying, “Well, since Copernicus thought the planets went around the sun, they have to go around the sun.” Without, you know, looking at the theory or worrying about whether it’s going to follow after you’ve made some predictions. If I just accepted it without any question, that would be an appeal to authority. So in science we always have to check the authority. He may be an authority but he may be wrong. And so we don’t just appeal to authority; we check the authority. There’s also superstition. One of the closest superstitions to astronomy is astrology. Some of you may not quite know the difference. Astronomy is the study of the university, the scientific study of the universe. Astrology is giving planets or positions in
Advertising tends to be an advocacy system. You see a famous football pla yer on television, drinking your favorite beer. It makes you think, “Well, maybe that’s pretty good beer. He drinks it.” Well, he’s advocating that you should drink that beer. Why? Well, maybe because he does like it or maybe just because he was paid a lot to say that. Maybe he doesn’t drink beer at all. You don’t know. Somebody’s advocating something, they don’t necessarily believe it’s true. They’re just telling you to believe that it’s true. So in science we try to avoid that. We try to actually find out what is the closest thing to reality. The worth truth is a little touchy but reality is about as close as you can come. The author ends the chapter by mentioning relativism. He mentions that there are certain educated people who believe that science or appeal to authority or superstition or the advocacy system — they’re all equal. It’s all relative. If we follow that completely, we could never know anything for sure. They may be different ways of knowing but they’re not all necessarily equa l. And so the author of your text does not believe in relativism — and frankly I don’t either. There are better ways of knowing and there are worse ways of knowing. Superstition and astrology are much worse than scientific method and astronomy. And I will advocate that.
