University:
York University
Course:
NATs 1745 | History of Astronomy
Academic year:

2023
Views:

459

Pages:

5
Author:

Nick T.

‭Understanding the Seasons: Earth's‬‭Tilt‬‭and Solar Patterns - Lecture‬ ‭Notes‬ ‭The Cause of Seasons:‬ ‭●‬ ‭Seasonal changes in the Sun's daily are due to Earth's 23.5° tilt‬ ‭The Sun and Latitude:‬ ‭Latitude (L):‬‭a location's angle N or S of Earth's equator‬ ‭ he lower your latitude, the higher the Sun's daily paths and‬ T ‭therefore the warmer the temperature‬ ‭The latitude of the North Pole‬‭=‬‭90 Degrees‬‭North‬ ‭The latitude of the Artic Circle‬‭=‬‭66.5 Degrees North‬ ‭The latitude of the Tropic of Cancer‬‭=‬‭23.5 Degrees‬‭North‬ ‭The latitude of the Equator‬‭=‬‭0 Degrees‬ ‭The latitude of the Tropic of Capricorn‬‭=‬‭23.5 Degrees‬‭Sout‬ ‭The latitude of the Antarctic Circle‬‭=‬‭66.5 Degrees‬‭South‬ ‭The latitude of the South Pole‬‭=‬‭90 Degrees South‬ ‭E.G‬ ‭-‬ A ‭ t 23.5° N (Tropic of Cancer), the‬ ‭noon Sun is in the Cancer‬ ‭constellation when the Sun is directly‬ ‭overhead (June Solstice)‬ ‭-‬ A ‭ t 23.5°S (Tropic of Capricorn),‬ ‭noon Sun is in Capricorn‬ ‭constellation when the Sun is‬ ‭directly overhead (Dee Solstice)‬ ‭-‬ P ‭ olar days and polar nights only‬ ‭occur within Arctic & Antarctic‬ ‭Circle; the higher the latitude, the‬ ‭more polar days/night‬ ‭The Celestial Sphere:‬ ‭ elestial Sphere:‬‭our view of the sky projected onto an imaginary‬ C ‭sphere to describe the positions of celestial bodies.‬ ‭ orizon‬‭: the circle around an observer that separates‬‭the visible and invisible‬ H ‭hemispheres of the sky.‬ ‭Zenith:‬‭the point in the sky directly above the observer.‬ *‭ The first exam in the course the first question is always: Where is the‬ ‭Zenith?* - The point in the sky directly above you (The observer).‬ ‭A celestial body's relative position is described by:‬ -‭ altitude‬‭: the object's‬ ‭angle upward from the‬ ‭horizon‬ ‭- azimuth:‬‭object's direction along‬‭the horizon‬ ‭- These cords can be used to help your neighbor identify the star or object‬ ‭Describing Lengths on the Sky:‬ ‭-‬ ‭Sizes & distances in the sky are expressed as the angle spanned:‬ ‭Units of Angular Measurement‬ ‭Degrees (°):‬ ‭●‬ ‭There are 360° in a full circle.‬ ‭●‬ ‭1° = 60 arcminutes (')‬ ‭Example:‬‭The distance between two stars can be a few degrees apart.‬ ‭Arcminutes ('):‬ ‭●‬ ‭A subdivision of a degree.‬ ‭●‬ ‭1° = 60'‬ ‭Example:‬‭The Moon's diameter is about 30'.‬ ‭Arcseconds ("):‬ ‭●‬ ‭A subdivision of an arcminute.‬ ‭●‬ ‭1' = 60"‬ ‭Example:‬‭Telescopic resolution is often measured in arcseconds.‬ ‭Practical Examples‬ ‭1.‬ ‭Full Moon:‬ ‭●‬ ‭Angular size is approximately 0.5° or 30'.‬ ‭2.‬ ‭Distance between Big Dipper's Pointer Stars (Dubhe and Merak):‬ ‭●‬ ‭Approximately 5° apart.‬ ‭3.‬ ‭Hubble Space Telescope Resolution:‬ ‭●‬ ‭About 0.05".‬ ‭Why Angular Measurement is Important?‬ ‭-‬ ‭Helps in identifying and locating celestial objects.‬ ‭-‬ ‭Allows astronomers to describe the relative positions and apparent‬ ‭sizes of objects in the sky.‬ ‭-‬ ‭Essential for tasks like star mapping, navigation, and understanding the‬ ‭scale of astronomical objects.‬