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Lesson 1: Introduction to Solar System Astronomy [Solar System Astronomy with Joseph DalSanto]


hello my name is joe delsanto professor of astronomy at the college of dupage and go now in illinois and i like to welcome you to our course on solar system astronomy we’ve got a lot of exciting things to learn about I like to think of astronomy as an adventure of the mind an opportunity for us to go places and learn things that we don’t normally see here on earth our solar system and the others will be examining have many wondrous things that have excited scientists throughout the world but the point of our course is to share much of that with you give you the opportunity to learn more about some of the exciting discoveries that we’re making as these things are not just for scientists but for everyone I’ve designed this course to be a concise introduction to solar system astronomy I really like to share my excitement my passion for astronomy with you I hope that you’ll enjoy the course and I hope that you’ll also consider perhaps our next course which will deal with stars and galaxies so what will our course deal with when we’re going to break the solar system into several regions first we’ll look at the inner solar system will consider the terrestrial planets Mercury Venus Earth Mars and our Moon we’ll look at other small bodies in the inner solar system such as asteroids then we’ll be progressing outward to the outer solar system the large jovian planets like Jupiter Saturn Uranus Neptune will finish up with an examination of small icy bodies in the outer solar system things like comets new objects that we found called Kuiper belt objects and yes everybody’s favorite the planet Pluto our course will then conclude with a brief look at other solar systems for centuries mankind has wondered could there be other planets in the universe well today we know the answer is yes and a whole new field has opened where we can examine and learn about these other solar systems so we have much to learn and I hope that you’ll enjoy the ride along with me during the course you’ll notice PowerPoint slides pop up occasionally that will provide you a little bit more information and some images that will supplement the discussion many times will get more information from these and that’s your opportunity to pause the lecture if you like to examine those slides for a moment or two before continuing some of you might be a little bit concerned about a science course thinking perhaps I’m not very good at math I’m not very comfortable with math well let me reassure you you won’t need any math for the course there will be a little bit that I’ll mention for those of you that perhaps have had some math and are comfortable with it but for those that have not again you don’t need to worry about the math it’s there merely to provide a little additional information the course can be enjoyed without math so how do we learn about the universe well simply put we use the scientific method science is a powerful and effective way for us to learn about the universe science look for natural explanations for what we see in the universe it progresses through the creation and testing of models or explanations of what’s really happening in the universe those models of course need to be tested we need to be able to determine if they’re right or wrong if they’re correct or not and that’s what scientists do they continue to make additional observations to see if our ideas are correct and so science is a very progressive way to learn about the universe if our model is correct great we’ll continue to test that will continue to learn more we’ll continue to make more observations but if by chance it’s not if our observations show that the model is not correct we may need to revise our model improve it change it or in some cases we may need to abandon it and start over with a new way to look at our observations let’s consider them a few steps in the process I mention that it really starts with observations of the natural world this normally generates questions why is this happening how is it happening where is it happening and in what manner is it happening all these questions begin to naturally arise and get our minds thinking about what might explain what we’re seeing and so an explanation makes begin to come to mind we call this a hypothesis what natural explanation might explain our observations once we have a hypothesis scientists as I said will then proceed to test the hypothesis think of a way to determine if this is correct or not this may involve additional observations it may involve other ways of going about that once again if our observations and our tests confirm the model great we go on we learn more but on the other hand if new observations disprove our model we may need to revise or change or possibly even abandon our model but ultimately when we get an explanation that does seem to give us a correct view of our observations this is when we begin to consider this a scientific theory now that word is used in everyday life but often it’s used in a different way people may say well that’s just your theory about a particular matter that is not the way the word is used in science in science a theory is a tested explanation others though may say well that’s okay but I believe in facts just present the facts to me so what is the difference between a fact and a theory well fact is a single proven piece of information that anyone can not only agree upon but proof or themselves a theory is built with fat x I like to illustrate it this way facts you might consider like bricks but a theory might be considered like a house that you would build with the bricks take these facts and we assemble them in such a way that they provide us a structure in which to understand the universe now maybe you’ve heard of scientific laws what are scientific laws well scientific law normally explains a relationship between two factors give you one example we’re going to be discussing the law of gravitation and in this case that law tells us how the strength of gravity changes with distance so that helps us see more clearly how the natural world works so to summarize a scientific theory must do three things number one of the most explain our observations correctly number two it must be supported by compelling evidence and number three it must not have failed any crucial test as to its validity once we have such a theory we can be confident that it is correct however it’s always open to further testing is it possible that someday the theory might be disproven yes that is possible but as of today we have certain theories that we accept as an explanation for what we see in nature what we’re going to examine a number of different concepts in the course I want to just very briefly touch on a few basic concepts that will help us in our discussion let’s start with something as simple as motion we’re all very familiar with motion we think of perhaps driving our cars we cover a certain distance in a certain amount of time while we’d consider that speed but more precisely scientists would use the term velocity what happens if we change the velocity we either speed up or slow down we would consider that an acceleration how about something called momentum we all kind of have a feeling for that we think of maybe driving your car on a rainy or snowy day and you say boy my car has a lot of momentum it might not be very easy to stop the car what is momentum well technically it’s divine as mass times velocity but essentially momentum comes in to various forms so to speak one would be momentum or motion in a straight line which again we think of a car perhaps but in astronomy we have a type of momentum that is more a circular motion we call this angular momentum because the body is moving through an angle I think perhaps of the earth against spinning on its axis it has a certain angular momentum think perhaps of the earth orbiting around the Sun it has a certain angular momentum so that type of concept will be important for us as we look at the solar system and how bodies move will also be considering energy now there’s three main types of energy that will be concerned about number one we’re all familiar perhaps with the energy of light we stand outside on a sunny day we feel the warm sunshine we realize there’s energy there it can warm something up or these days perhaps we take outside a solar panel and capture the sunlight and that device is able to change it into electricity well that electricity can be used for various other purposes and that leads us to our second type of energy kinetic energy is kinetic energy well this is energy of motion again think of a car or an object in motion this depends on the mass and on the velocity as well we might think of perhaps taking that electricity from our solar panel converting it to electricity and perhaps it may drive our cars down the street or perhaps we use it to turn an electric motor that may move of an object so we can actually convert the radiative or light energy into the motion or kinetic energy we have one more type of energy that’s important in astronomy it’s called potential energy and we think of that as stored energy here we might against store energy that’s been captured from the Sun and a battery what could we do with that energy well again we might turn a motor we might do other things with it or we may very simply take a object and use that electricity use that energy to raise it to a higher level I think perhaps of going to the amusement park maybe we get on the roller coaster and the electric motor takes that roller coaster up to higher level doesn’t it well you know what happens when they release you and the roller coaster begins to come down it accelerates it speeds up where does it get that kinetic energy while it had stored energy potential energy at the top of its path and that again can be changed into kinetic energy so we’re just introducing some concepts here that are going to help us as we move along we’ll explain them a little further as we do go along another concept that will be important in our study of the solar system is gravity I perhaps you associate that term with Isaac Newton you first discovered that law long ago we still use his equations as a very good approximation there are better theories frankly but Isaac Newton’s theory still works quite well as a good approximation of how gravity works noon discovered the two bodies have a naturally attractive force between them and the strength of that force depends on how massive each body is and on the distance between them so there’s a very simple equation that describes this again the larger the mass the greater the force the closer the distance the greater the force that will be important as we consider how the planets orbit the Sun moon’s orbit planets and so on and so forth we’ll also be very concerned with light light is very essential in astronomy why is that well when you think about it there’s very few objects in astronomy that we can go study firsthand we are able to send space probes to a few nearby objects but we really can’t necessarily go examine them up close instead we have to rely on the light that we receive from those bodies to study them what light has various properties the ones will be interested in include wavelengths or how long or how large the light waves are so to speak we’ll also talk about frequency how quickly how frequently the light wave passes by you and we’ll also talk about the energy of the light as we mentioned a few minutes ago now there’s a very interesting relationship between the wavelength and the frequency and mathematically wavelength times frequency equals the speed of light now the speed of light is a constant it never changes and so therefore you can imagine that if the wavelength is a larger number well the frequency must be a lower number in other words if our frequency is lower our wavelength is longer and vice versa if our wavelength is shorter or lower our frequency must be higher so you begin to see how these things work together we can utilize those again in our studies of astronomy so you’ll also see at the end of each lecture they’ll be a brief review let me go ahead and review the few things we’ve talked about so far what is needed to study astronomy and in particular our solar system well I think we mentioned beginning it starts with curiosity doesn’t it we make observations of the natural world those observations lead us to ask questions those questions lead us into the steps of the scientific method we begin to formulate an explanation a hypothesis we then test that hypothesis whether it’s correct or not and eventually we hope to arrive at a true and correct explanation of what we’ve observed we call that a theory and we’ll be seeing at least one and more theories as we move along we touched on some basic concepts didn’t we we looked at things like motion energy gravity and light to kind of set the stage and give us some tools so to speak to be able to use in our expiration and we did see at least one or more natural laws that will allow us to understand the universe so we’ve got lots to look forward to I’m glad to have you long hope you enjoy the course let’s get started you

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