PPT-Astronomers measure large distances in light years. 1 light

5880000000000 miles or 588 trillion miles The Milky Way The Greek philosopher Democritus 450370 BC proposed that the bright band on the night sky known as the Milky Way might consist of distant stars Aristotle 384322 BC however believed the Milky Way to be caused by the ignition of the fiery exhalation of some stars which were large numerous and close together and that the ignition takes place in the upper part of the atmosphere in the region of the world which is continuous with the heavenly motions The . Recap. Canvas homework due Wednesday. Lab this week: Parallax. Overview of the Universe. Solar System, Galaxy, Universe. Largest scales. Expanding Universe. Evidence for a Big Bang. Evidence for an accelerating Universe . Recap. Distances in astronomy. Measuring distances directly with light travel time. Measuring distances geometrically with parallax. Measuring distances using . brightnesses. Distances using brightnesses. Where do you live? Your home or your school has an address: a street, a city or town, and a country. When someone . sends . you a letter, they . write . your address, so that your mail carrier knows the letter should go to you. For example, the address of Brookside School is: . Key Ideas. Distance is the most important & most difficult quantity to measure in Astronomy. Method of Trigonometric Parallaxes. Direct geometric method of finding distances. Units of Cosmic Distance:. The stars and other objects in space are very far from Earth. Only a few solar system objects are close enough to be explored with probes. . Astronomers rely on electromagnetic waves to gain information about the universe.. Science 9. Using scientific notation. Distances in space are very large. We use scientific notation to represent very large and very small numbers. The first digit is between 1 and 9. This is called the base. Where do you live? Your home or your school has an address: a street, a city or town, and a country. When someone . sends . you a letter, they . write . your address, so that your mail carrier knows the letter should go to you. For example, the address of Brookside School is: . Scientific Notation. Power. of 10. Decimal Equivalent. 10. 7. 10 000 000. 10. 4. 10. 000. 10. 2. 100. 10. -5. 0.00001. 10. -7. 0.0000001. Scientific Notation. This is a number in scientific notation:. Scientists (and the world) use the metric system. Units. Convert km to miles = multiply by .6. Convert meters to feet = 3 ft / meter.. Scale Model of Solar System. Solar System Distances. Kilometer is too small. 150,000,000 km to Sun.. An . Astronomical Unit . (AU) is defined as the average distance between the Earth and Sun. . . 1 AU = . 92 955 807 miles . or . 149 597 871 km. AU’s are used to measure distances within the solar system. . RADIO WAVES. HOW DO RADIO WAVES HELP ASTRONOMERS. Astronomers learn about a stars composition, structure and motion . MICROWAVES. HOW DO ASTRONOMERS USE MICROWAVES. ASTRONOMERS PICK UP THE COSMIC MICROWAVE BACKGROUND THAT WAS LEFT OVER FROM THE BIG BANG. . Light Year. How far is far?. How fast is fast?. What Is It?. A light year is the . . DISTANCE that light . . will travel, through a . . vacuum, in . one . year.. Calculate Seconds. . How many seconds are in a year? . Night sky rule of thumb. :. one finger width = 2 deg. . one hand width = 10 deg.. Units for Time and Distance. Kilometer (km). = .621 miles. Light-year (. lt-yr. ). = The distance light travels in one year in a vacuum. . The Universe. Where are we?. Metric System: 1000m = 1km. Astronomical Unit (AU): Earth to sun = 1 AU (1.496 x 1011 m). ***Light Year***: Distance Light travels in ONE year! . (9.46 x 10. 12. km). Parsec: parallax-second (3.08 .