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In This Lesson: Unit 1 The Scale of the Universe (Lesson 1 of 2) Today is Monday, th April 10 , 2017 Pre-Class: What is astronomy? Put your syllabus receipts in the Turn-In Box. http://apod.nasa.gov/apod/image/0708/M67_Greg_Noel.jpg Messier 67 (M67) Star Cluster (at center) Today’s Agenda • • • • Astronomy Pre-Test. The Scale of the Universe. Scientific Notation. Really long distances. • Where is this in my book? – Pages 6-15. By the end of this lesson… • You should be able to describe measurements in scientific notation. • You should be able to measure astronomical distances in three units. Astronomy Pre-Test • Before we start this class, I’d like to know what you know. • Do your best on this pre-test, but it won’t affect your grade. – You’ll also be the one grading it. • Once you complete all questions, put your pencil down. What is astronomy? • Astronomy seeks to understand the structure and evolution of the physical universe. • Doing so also helps us to understand the origin of life in the universe. http://apod.nasa.gov/apod/image/0708/m17x800ignacio.jpg Messier 17 (M17) Nebula Perspective • Ever looked at the stars at night? – There are about 6000 “celestial objects” visible with the naked eye from somewhere on Earth. – Pennsylvania gets a view of about 75% of the sky throughout the year, so you can see about 4500 objects. – Of the 4500 visible objects from Pennsylvania, only 7 objects are not stars. Perspective Visible Objects That Aren’t Stars (and not Earth) • • • • • • • The Moon Mars Jupiter Saturn Venus Mercury The Andromeda Galaxy Galaxies and Stars • Now might be a good time to tell you that a galaxy is different from a constellation. – A constellation is a relatively small group of stars that can be connected with lines to make a shape. • Like a crab or a goat or something. – A galaxy is a large group of stars (on average 400 billion) that you really don’t connect. • Because it would look like the Mona Lisa, if painted by a two-year-old amputee. – Need I remind you that our own galaxy is known as the Milky Way? Perspective • So, that makes us a very small part of the universe. • Want some more perspective? – The Scale of the Universe – Scale of the Universe.lnk • Want even more perspective? – Cosmos – Our Cosmic Address • FYI, you probably already know this, but “everything” is known as the universe. – The universe is about 13.8 billion years old, which is kinda hard to wrap your head around. For some help: – Cosmos – Cosmic Calendar Scales • Perhaps the most important thing to know going into astronomy is how things are measured. • Simply put, celestial bodies are so ginormous that it’s difficult to measure things. • We’ll learn a lot of the measurements throughout the course, but we’ll start with two important things: – Scientific Notation (in general). – The Light Year, the Parsec, and the Astronomical Unit. I get it…now what? • Numbers written in scientific notation take this form: • M x 10n – M is between 1 and 10 (1 or above, less than 10). • M is sometimes called the mantissa or significand. – n is an integer. • This allows you to take measurements of either extremely large or extremely small numbers. – In our case, mainly extremely large. 2,500,000,000 Converting to Scientific .Notation 9 8 7 6 5 4 3 2 1 • Make 2,500,000,000 into scientific notation. – Step 1: Put in an understood decimal point. – Step 2: Decide where the decimal point must end up so that there is only one nonzero digit to its left (M). – Step 3: Count how many places you have to bounce the decimal point to get there (n). – Step 4: Rewrite in the M x 10n form. 2.5 x 9 10 Converting0.0000579 to Scientific Notation 123 4 5 • Make 0.0000579 into scientific notation. – Step 1: Put in an understood decimal point (already done). – Step 2: Decide where the decimal point must end up so that there is only one nonzero digit to its left (M). – Step 3: Count how many places you have to bounce the decimal point to get there (n). – Step 4: Rewrite in the M x 10n form. -5 5.79 x 10 Practice • Scientific Notation worksheet – Try #1-12. Scientific Notation • Remember that moving the decimal point left makes n go up by one; moving it right makes it go down by one. • Since you now know how to write in scientific notation, let’s talk about how to calculate in scientific notation. • We’ll start with addition and subtraction. Addition and Subtraction • If the exponents are the same, simply add or subtract the (M) numbers in front and leave the x 10n part unchanged. • You can do this for addition or subtraction. 4 x 106 + 3 x 106 7 x 106 4 x 106 - 3 x 106 1 x 106 • Addition and Subtraction 6 4 x 10 If the exponents are not 5 + 3 x 10 the same, we have to move a decimal point until they are. • Move the decimal on the smaller number! 4.00 x 106 + 3.00 x 105 4.00 x 106 + 0.30 x 106 6 4.3 x 10 Practice • Solve the following in scientific notation: 2.37 x 10-6 + 3.48 x 10-4 -6 2.37 x 10-4 0.0237 + 3.48 x 10-4 3.5037 x 10-4 Multiplication and Division • For multiplication, just multiply the digits in front (M), then add the exponents (n). • Remember that you still need to make sure the number in front (M) is between 1 and 10. 8 x 103 x 3 x 109 24 x 1012 13 2.4 x 10 Multiplication and Division • For division, do the opposite of multiplication. • Just divide the digits in front (M), then subtract the exponents (n). 6x 8 10 /2x 7 10 = 3x 30 1 10 Practice • Solve the following in scientific notation: 2 x 10-2 / 5 x 10-6 = 0.4 x 104 3 4.0 x 10 One final note… • You may notice your calculator giving you answers like this: • 5.665 E 8 • 5.665 8 • In both cases, your calculator is trying to say: • 5.665 x 108 Practice • Scientific Notation worksheet – Try #1-5 (lower section). • Now to challenge yourself: – Try the back, odd numbers only. – Stuck? Ask. Other Scientific Notationworthy Measurements The Units of Astronomy • There are several important astronomical units out there, one of which we’ll be focusing on now. Here are the big three: – The light year. – The parsec. – The astronomical unit. • Let’s define them in reverse. The Units of Astronomy Astronomical Units • An astronomical unit (AU) is a very large distance used to describe space stuff. – Cause space is, you know, big. • It was originally defined as the distance between the Earth and the Sun, but there’s a problem. – The Earth and the Sun are not always the same distance apart. • So, the official designation of the AU is: • 149,597,870,690 meters • That’s about 150,000,000 km or 93,000,000 miles. The Units of Astronomy Astronomical Units • For perspective, if the Earth were a ping pong ball… • …the Sun would be about 9 feet across… • …and located around 900 feet away. • That’s an astronomical unit! The Units of Astronomy Parsecs • A parsec (pc) is 3.26 light years (more in a moment), or 3.086 x 1016 m…but it’s a little bit more complicated than that. • The term comes from “parallax” and “arcsecond,” which are both terms used to measure the movement of celestial objects against a background. • Let’s see if we can learn a little more: – UniverseToday – What is a Parsec? • You should understand the concept of a parsec, but don’t worry about how to calculate it. http://www.universetoday.com/32872/parsec/ About Parallax • In short, parallax is the idea that objects may appear to “move” based on the position of the observer. – For example, imagine looking at any two other desks in this room. • The left one’s on the left, the right one’s on the right. – Walk to the other side of those desks, though, and sudden the one that was on the left is on the right, and vice versa. • That’s parallax. Parsecs and Parallax • Parsecs attempt to quantify the distance to a celestial object by using parallax. • Once you get the parallax “distance” (seconds), you can use trigonometry to calculate the distance to the object. – Effectively, you do triangulation. – But how do you get the parallax distance? Arcminutes and Arcseconds • To help map out the sky, astronomers divide the entire celestial sphere into 360 equal slices (360 degrees). – Each 1° of sky is 60 arcminutes. – Each arcminute is made of 60 arcseconds. – So an arcsecond is 1/60 of an arcminute, or 1/3600 of a degree. • The sec of arcsecond and the par of parallax is where we get parsec. Parsecs • Pythagoras would be proud! Stellar Parallax • Stellar Parallax Interactive The Units of Astronomy Light Years • A light year (ly) is the distance light travels in a year (in a vacuum). • NOT A TIME UNIT! • Light travels at 186,282.397 miles per second, or 2.998 x 108 m/sec. • As you might guess, light is so fast that a light year is a REALLY LONG DISTANCE. – It’s 62,239.72 au, but there’s something even cooler. • Let’s look at this with an example. The Units of Astronomy Light Years • Which comes first, thunder or lightning? – Lightning, but technically only by an instant. • Lightning is so hot that it causes the air around it to rapidly expand and move faster. – All those air molecules hitting one another causes thunder. • The thing is, if you’re far from the impact point, it could take a few seconds to hear thunder after seeing lightning. – Sound takes about 5 seconds to travel one mile through air, so if it takes (for example) 10 seconds to hear thunder after a lightning bolt, you know the strike was 2 miles away…approximately. The Units of Astronomy Light Years • You may also experience this in a big building like a stadium. • During baseball games, you might see the bat hit the ball, but you don’t hear the sound for a second or two. – Since light travels so much faster than sound, by the time it gets to you it looks “out of sync.” http://www.stadiumpage.com/stpages/Shea_Upper.html The Units of Astronomy Light Years • It’s important to remember that light does not move instantaneously. • It just seems that way here on Earth, across relatively very small distances. • However, because it takes a few moments to reach your eye, technically, you are always… • …LOOKING BACK IN TIME! • For more, let’s revisit UniverseToday. The Units of Astronomy Light Years • Yet another example: – In July of 1054, Chinese, Japanese, Korean, and Arab astronomers reported seeing a “star” appear in the sky that was so bright it was visible in daylight. – We now know it was the explosion from a supernova that created M1, the Crab Nebula. https://upload.wikimedia.org/wikipedia/commons/0/0f/CrabNebulaH ubble.jpg http://chandra.harvard.edu/chronicle/0406/historical_snr/SupernovaCina.jpg The Units of Astronomy Light Years • The Crab Nebula is 5000 light years away from Earth. • Therefore, even though astronomers recorded the event as “happening” in 1054, in reality the event occurred 5000 years prior (~3946 BC). https://upload.wikimedia.org/wikipedia/commons/0/0f/CrabNebulaH ubble.jpg http://chandra.harvard.edu/chronicle/0406/historical_snr/SupernovaCina.jpg The Units of Astronomy Light Years • Still another example: – The Pillars of Creation, a part of the Eagle Nebula, is visible to the Hubble Telescope. – In reality, it’s likely gone, destroyed by a nearby supernova. • Except the light from that event hasn’t gotten here yet. http://alexpetrov.com/memes/astro/deepfield.jpeg The Units of Astronomy Light Years • Now to put that knowledge to practice. • Let’s get a sense for how far a light year is. – How Long is a Light Year worksheet Other Methods of Scaling • So light years, parsecs, and astronomical units are all units of distance. • Parallax is a method of measuring that can be converted to those units of distance above. • There’s one problem, though: – Parallax only works for objects that are, well, relatively close. – Here are some alternate methods along with sample celestial bodies. Aside: Space-Time • You might be aware of a somewhat similar phenomenon called “space-time.” • In short, the part of it you’re thinking of is the idea that time passes at different rates based on gravity. • You might have even seen a movie dealing with the concept of space-time as a central plot point… Maybe you remember this? Aside: Space-Time • Space-time isn’t something within the scope of this course (more a physics thing), but here’s your brief summary anyway: – Space-time is the idea that “time” is not separate from space. • In other words, it’s a little like adding “time” to a coordinate system that also features latitude and longitude. • Space-time is therefore a four-dimensional object. – Einstein’s Theory of Relativity does much to explain the idea of space-time. – According to Relativity, time passes more slowly in high-gravity areas like places near black holes. http://www.space.com/27692-science-of-interstellar-infographic.html Closure • From this lesson, I hope you take something rather important away: – A frame of mind. • Throughout this course (and your life), try to remember that the universe is so big that it’s nearly impossible for humans to actually perceive all of it. Closure • Look up and realize that, in the direction you’re looking, the universe goes on… • …and on… • …and on… • …virtually forever. Until you get to a point so far away that no signals from it have yet even reached us, making it truly “non-observable.” – The Scale of the Universe one more time… – Scale of the Universe.lnk Closure – One Last Thing • Let’s play a little game called “Small/Large and Near/Far.” • Credit where credit’s due: – This comes from Cherilynn Morrow, Ph.D., at the University of Colorado. Small/Large and Near/Far • Get a scrap piece of paper and make two columns: Smallest Small/Large Near/Far 1. 1. 2. 2. 3. 3. 4. 4. 5. 5. 6. 6. 7. 7. 8. 8. Largest 9. 9. Nearest Farthest Small/Large • On the next slide you’ll see nine images/objects/things. • Using the left column, rank them from the smallest to largest object. • Write the letter of the object and the name. • If anyone gets all nine correct in order, s/he will win 500 imaginary bonus points. A. The Sun B. Earth D. The Moon E. The Solar System G. Mars H. Galaxy C. Space Shuttle F. Bears I. Jupiter Small/Large: Solution 1. F. Bears 2. C. Space Shuttle 3. D. The Moon 4. G. Mars 5. B. Earth 6. I. Jupiter 7. A. The Sun 8. E. The Solar System 9. H. Galaxy Near/Far • On the next slide you’ll see nine images/objects/things. • Using the right column, rank them from the “nearest to Earth” to “farthest from Earth.” • Write the letter of the object and the name. • If anyone gets all nine correct in order, s/he will also win 500 imaginary bonus points. – So you could get 1000 imaginary bonus points total! A. The Sun B. Galaxy D. The Moon E. Jet Airplane G. Eagle H. Stars of Ursa Major C. Aurora Borealis F. The Hubble Telescope I. Saturn Near/Far: Solution 1. G. Eagle 4. F. The Hubble Telescope 7. I. Saturn 2. E. Jet Airplane 3. C. Aurora Borealis 5. D. The Moon 6. A. The Sun 8. H. Stars of Ursa Major 9. B. Galaxy Near/Far: Solution Notes 1. The highest bird ever encountered in flight was at 37,000 ft. 2. Jet airplanes typically fly in the stratosphere (more than 10 km/6 mi up). 3. Auroras occur at the highest reaches of the atmosphere (95190 km/60-120 mi). 4. The Hubble Telescope is 600 km/373 mi away. 5. The Moon is 400,000 km/250,000 mi. 6. The Sun is 1 AU (150,000,000 km/93,000,000 mi). 7. Saturn is between 9 AU and 11 AU away. 8. Stars of Ursa Major (the Big Dipper) are at least 70-100 light years away (the closest ones). 9. NGC 4414 (Galaxy) is 60 million light years away (you can’t get an image like that of our own galaxy). Closure • How Do We Measure Distance In The Universe? Other Closure Videos UniverseToday • • • • • • • • How Far Can You See In The Universe? How Long Does It Take Sunlight to Reach Earth? Are Aliens Watching Old TV Shows? How Big is the Solar System? How Big is the Universe? How Far is the Earth from the Sun? How Long Does it Take Sunlight to Reach Earth? What is the Distance to the Moon? Closure • Looking Out is Looking Back Hyperspace • Star Stuff • Are We Alone?