HIST2620 1nd Edition Lecture 2 Outline of Last Lecture I Our Cosmic Address II Our star The Sun III Our solar system IV Dwarf Planets V Scales of size and time VI Metric system VII Light Year VIII Light IX Speed of light CALCULATION X Solar system XI REVIEW Outline of Current Lecture I Review Chapter 1 II Scientific method III Hypothesis theory and law IV Scientific Models V Constellations VI Magnitude scale VII Celestial Sphere Current Lecture I Review Chapter 1 6 7 x 105 6 7e 5 Which of the following is the greatest distance o The Distance from the earth to the sun No unit conversions on the test no calculator needed for test These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III IV V Scientific method Observations of nature and then we reflect why and how they could work Why it works that particular way in nature IT MUST BE TESTABLE has to either agree or disagree to test the viability of the explanation After this testing the results have to disagree or agree After this this is just a possibility now There are more possibilities of hypothesis Observation and experiment Astronomy uses a lot of observation rather than experimentation Hypothesis theory and law Sort of high school stuff forming simple hypothesis then do experiment and either restate hypothesis or redesign experiment Theories are much more highly tested generalized Theory have been tested expanded and generalized HAS BEEN TESTED HAS NOT BEEN FOUND TO BE INCORRECT AT ANY POINT Natural Law theory has been refined tested Generally accepted o Ex Newton s law of universal gravitation Used to plot the paths from earth throughout the solar system Still used was originally developed from pen and paper o Einstein s law is now considered our law of universal gravitation Works in many more circumstances Changes out understanding of universal space and time More all encompassing Scientific Models Help us visualize and understand motion how things work in nature They do not have to be based on correct assumption Many are seriously flawed but don t mean they are useless Can help explain and understand things o The idea that we are the center of the universe obviously wrong but help us understand the constellation placement and movement Looking at the sky o Sun Moon rise in the east and set in the west The Stars rotate in a counterclockwise motion around the sun Constellations Observation o Instead of looking south look north You will see the North star Polaris and the stars will make a counter clockwise circle around this Circumpolar stars do not move Everything east and west will move because we are rotating the star directly above us doesn t appear to move VI VII o Ursa minor doesn t appear to move because it has Polaris in it Ursa major is not circumpolar for Texas o Cassiopeia is also circumpolar As viewed from earth most dots do not appear to move with respect to each other 5 naked eye visible planets Ancients connect these stars in a way that connected to their culture Tended to link similar stars together A way to tell time changing of the seasons and also to navigate A star chart today you ll see squares with dots in them they will be labeled One big chunk is a constellation This has changed with the development of communication to standardize the constellations Now each star is in one and only one constellation o DON T NEED TO KNOW ALL CONSTELLATIONS FOR THE TEST How big the stars appear depends on how you look at them If you look at big dipper stars they do look like a certain shape From a different direction they view can change the way the stars are aligned WHAT MAKES POLARIS A SPECIAL STAR o It is currently near the axis about which the sky turns o Its azimuth direction is due north Magnitude scale The real difference between appeared brightness between 2 1 2 5 1 st 6th is 100 o Its on a log arrhythmic scale that is backwards scale to most people but that s because 1st is the MOST BRIGHT just like 1st place in a race 0 is Polaris so there are negative magnitudes which mean they are brighter than Polaris This is the BRIGHTNESS WHEN VIEWING FROM EARTH Apparent magnitude scale does not take into account distance whatever is closest appear the brightest Hotter stars also give out less visible light even though it is bigger brighter store Humans are lazy so we don t change the star charts Cool stares may also not be rated properly Celestial Sphere Assumes that the sun moon and planets rise east set west Unaware of earth s rotation Moves through one constellation about every month These are called the Zodiac constellations astrology routes The ecliptic is marked by the sky by the zodiac Always have to have a reference to measure any place on earth Longitude measured from prime meridian Latitude measured from equator Vernal equinox change from winter to summer Polaris sits at north celestial pole No pole star in the south GLOBAL Coordinates of stars o Declination how high above the equator o Right ascension measured in 24 hour period Related to rotation of the earth Local coordinates o If at North Pole stars were so far away would see everything north of the celestial equator over the course of a year o Zenith horizon is the plane through the center of the earth to the northern star in the sky Horizon is perpendicular to the Zenith If you just keep your latitude the same that half of the sky horizon will stay the same o Meridian line connecting Zenith point and the Horizon Line of right ascension Am pm is related to the observer s meridian Keep the sun close the observer s meridian during the daylight hours o Measuring degrees without tools Use fist fist with thumb extension and diameter of moon to be about width of thumb Fist is about 5 arch degrees you just need to calibrate it yourself with these goals Rotating sky explorer o How do you see your stars move Earth rotates every 24 hrs will not see the same stars is you move north and south If at the North Pole true zenith is Polaris and the rise set stars will define the horizon If at equator then the north south celestial poles would be in front of you and you would see almost a full sky view Up and down latitude you lose stars On TEST how view of sky changes Latitude MATTERS longitude does not matter Because you will see the same horizon and view due to rotation of earth Questions o From what location on earth is north celestial pole visible From the equator