 Greetings and welcome to the Introduction to Astronomy. In this lecture, we are going to discuss astronomy and astrology. So what are the differences and what are the similarities between these two? And we'll look at how that has changed over time. What we see is a very distinct difference today. Any astronomer would not want to be called an astrologer. We could find that to be very offensive, that astrology is something that is not even considered a science. However, not that long ago, as in hundreds to a thousand years ago, there was little difference between an astronomer and an astrologer. So what we're going to look at in this lecture is take a little bit of a look and compare how these work and how they have changed over the ages. So starting off, let's look at some of the basics. What do we mean by astronomy and astrology? Well, astrology itself here is, what do we mean by it? It is the studies of the different objects that wandered through the sky. So there were seven known objects that wandered through the sky separate from the stars. The stars always retained their same positions relative to each other. So the constellations that we saw were always exactly the same. However, there were seven objects that wandered through these and these gave us our days of the week. And these objects were the sun, the moon, Mercury, Venus, Mars, Jupiter, and Saturn. So the sun and the moon and the five planets that were known. And they wandered through the sky so they had special importance and had special significance to ancient peoples. Now the beginnings of this, again, were quite different than what we look at today. And it was thought that these could have an impact on peoples' lives so that they could affect how peoples' lives worked and could make predictions of what would happen in someone's life based on the positioning of the stars. So some of the things that we know on astrology you may be familiar with and that would be the constellations of the zodiac. So you're probably familiar with these. The constellations of the zodiac are actually astronomical in nature. So we have our term zodiac there. But they are actually astronomical in nature. You will recognize these if you've ever followed a horoscope at all. Things like Aquarius, Pisces, Ares, Taurus, and so on. What was so special about these constellations? It's very interesting because they are not the brightest constellations in the sky. In fact, some of them have very few bright stars. Pisces, for example, Ares do not have any really bright stars. Neither does Cancer and Libra. A lot of these have very few or no bright stars in them. Others might have a couple bright stars, but they were important not because of what the stars were made up of, but because of where they were located. And these are the constellations that the sun, the moon, and the planets will move through over the course of the year. So why did they become important to astrology? Is that they were the constellations where you would find these wandering objects. Where you would find the sun, where you would find the moon, and where you would find the planets were all within the twelve constellations of the zodiac that we see here. Now what is really happening there, if we want to look at reality, is that the sun and the moon and the planets are not moving through those constellations. What is actually moving is the earth. So the earth's motion is changing the position of the sun. So we would see, because here's the sun and here's the earth, so in January we see the sun towards the constellation of Sagittarius, and we would see other constellations high in the night sky. So this would tell us what constellation the sun is in. But it's the earth that's doing the moving, so that a few months later we would be over here and now instead of seeing the constellation of Sagittarius as the location of the sun, we would see Aquarius and then a couple months later we would see it as Aries and so on around and repeating this cycle every year. So that causes the changing position of the sun in the sky. So the sun appears to move through the constellations and what would your sun sign would be the location of the sun on the day you were born. Now, we also know that the solar system is flat, that if you draw it on a piece of paper that's a pretty good approximation of reality, and that means that the planets will also follow this same path. So not only does the sun go through these 12 constellations, but so will the moon and the planets. So let's look a little bit more about what this means for astrology. And we look at natal astrology, which was one of the early astrologies here, and that was where were these objects at the moment of your birth? So exactly when you were born, not just where was the sun as in your solar astrology, but where was the moon and where were the five planets at that time? And that was said to determine what your personality would be and what your life would be like. Now, you note that's quite different from the astrology that you tend to look at today. Today you look at astrology, you know, you get a couple sentences based on the month in which you were born and what constellation that is associated with. The original astrology was much more complicated looking at not just the position of the sun here, but also the moon and the planets. And those would all have an impact on your personality and your destiny. Now, this was developed by the Greek astronomers that we've talked about in previous lessons. And Claudius told me one of those astronomers that we talked about actually wrote a treatise on astrology as well. We talked about his Almagest, which was his great work that explained the motions of the planets and how to be able to predict those. But this is really the basis of astrology today is still based on this work of Ptolemy. And at Ptolemy's time there was really little difference between astronomy and astrology. And I mentioned that before. They were essentially one and the same and that an astronomer and an astrologer were quite the same. And that is very different than what we have today. So let's take a look at some of these horoscopes and what we can do. The sky for a horoscope, the sky is divided into 12 sections. So when we look at a horoscope, we have 12 sections and these are the constellations of the zodiac. On average, the sun spends about one month in each constellation. Now, that's on average. In reality, if you look at the horoscopes, they are all divided into one month sections. In reality, if you look up where the sun is, the sun can spend as little as a week in some of the constellations and it can spend more than a month in other constellations. So in reality, they're not actually uniform. Now we also have talked about precession. What is this due to the horoscopes? Remember that precession is slowly changing the position of the Earth's celestial poles. So it's changing the coordinate systems and changing the positioning that we see. That has, since the time of Ptolemy moved us about one zodiac sign off from what the Church would say. So for example, if you look up May 6, that would normally you consider someone a Taurus who was born on May 6, but the sun on that day would be in the constellation of Aries still. So we're about one constellation off because of precession slowly changing the coordinates and slowly changing the positioning of the constellations over time. So what we used a thousand years ago is quite different than what we would have to use today, but we're still base our astrology is still based on the original horoscope. So if you're born on May 6, you're considered a Taurus. However, the sun was truly in Aries when you were born. So what this means is that the newspaper or internet horoscopes that we may look at are based on just the sun sign. Where was the sun when you were born and where was it according to the ancient horoscopes? This would mean that essentially 8% of the population has exactly the same horoscope prediction every day. So almost 1 in 10 people will have the same prediction as you and it'd be odd that 10% of the people, hundreds of millions of people would have exactly the same day. That would not be something that would be scientifically possible. Now in truth, that is very simplified. That is not what a complete horoscope would be. If you do a complete horoscope, again, you use not only the sun, which is the sun sign. That's when you look up that small brief blurb that says what your day is going to be like. But you also look up the moon and each of the five known planets that would then give you, tell you a lot more information about how your life would go. So it also has to be interpreted and it does depend on judgment as well. So this is kind of what removes it from being a science. Is that there is a lot more judgment involved and that the interpretation can vary from astrologer to astrologer. So one person may interpret the position of Jupiter when you're born as one thing and another one may interpret it slightly differently or somewhat differently. And that gives a sort of flexibility in the horoscope, but they don't necessarily match up exactly. There is not an exact position that says if Jupiter is exactly here at this location, then this is what will happen. There is some judgment there and that kind of removes it from being a science like astronomy which would predict specifically where the planet is going to be and your model would have to then show that. Now let's look at how these are have adjusted over time. Again, from the ancient Greeks the time of Tome until the Renaissance these were really very similar things and by that I mean that astrology and astronomy were not all that different. People like Tycho, Kepler, and Galileo actually cast horoscopes as well and were astrologers in addition to being astronomers. How well they actually believed in the astrology is a good question and may be questionable, but they did cast horoscopes based on what Tome had done before. Shortly after that by the 1700s they began to diverge and became separate. Astronomy was simply the study of the sky. Astrology was the study of the sky's perceived impact on our lives here on Earth. So how did those positionings affect us here on Earth? Astronomy would study and predict where the planets would be. Astrology became how those would impact us here on Earth. So by the 1700s these were beginning to diverge significantly and there was a big difference at that point between an astronomer and an astrologer. Now we look at astrology as being a pseudoscience and what do we mean by that? Well, a pseudoscience here is a subject that seems to be scientific or purports to be scientific and it may use scientific terminology. A lot of the terminology of astrology and astronomy is very similar. That terminology is the same. However, astrology is not based on rigorous testing. So a pseudoscience would not have the same rigorous testing that an actual science would. When we try to make predictions of the positions of the planets we make those predictions and then we test them out and find out are they correct? Is our model correct or do we need to make modifications to it? Statistical studies done on astrology have shown that there is really a relationship between someone's horoscope and their lives. In reality, most horoscopes if you read them are vague enough that you can find some truth in it. You will find something that happens to you perhaps that day that fits and that you could then interpret to fit with the horoscope. But in reality if you cast the actual horoscopes, the full horoscopes, the predictions are no better than random chance. And that would be that what are these astronomy is really astrology is the study of the perceived impact of the positions of these seven objects here on our lives. Astronomy on the other hand is just the study of the celestial objects and their positions. Note the difference is this impact that this impact on our lives is not something astronomers even consider. So whether they are is not considered to have any impact on our lives. What we looked at was that astrology and astronomy were really very similar in the distant past. And there was times, even again just a few hundred years ago where astronomers and astrologers were one and the same person. Statistical studies have been done to look at astrology and have found that there is really no scientific basis for it that the predictions that are made show no better than random chance of coming true. So therefore give no predictive value to your future and your life. So that concludes our discussion of astronomy and astrology. And looking at the example of astrology as a pseudoscience. We'll be back again next time to discuss some of the other astronomy. So until then have a great day everyone and I will see you in class.