1 / 9

Ch. 1 Charting the Heavens

Ch. 1 Charting the Heavens. Our Place in Space - vocab. Universe: totality of all space, time, matter and energy Astronomy: study of the universe Light year: distance light travels in one year, equal to 300,000 km/sec (Earth’s diameter is 1/20 th of a light-second ). Constellations.

manny
Download Presentation

Ch. 1 Charting the Heavens

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ch. 1 Charting the Heavens

  2. Our Place in Space - vocab • Universe: totality of all space, time, matter and energy • Astronomy: study of the universe • Light year: distance light travels in one year, equal to 300,000 km/sec (Earth’s diameter is 1/20th of a light-second)

  3. Constellations • We recognize 88 constellations • Most of the constellations we know are from the Greek/Roman era • However, many cultures had constellations, some using the same stars • The Big Dipper is: • The “plow” or “wagon” is Western Europe • The leg of an ox in Egyptian mythology • A stag in Siberia • A funeral procession in some Native American cultures

  4. The Celestial Sphere • The ancient Greeks believed that a transparent globe surrounded the Earth, to which the stars were attached. • This globe revolved around the Earth, making the constellations move. • Celestial poles: points where Earth’s axis intersects the celestial sphere

  5. Earth’s Orbital Motion • Solar day: 24 hrs • Sidereal day: a day measured by the stars, 23 hrs, 56 minutes long • Why the difference? • Earth moves in its orbit as it revolves around the sun • How many degrees does Earth rotate per hours? • 360 ̊ /24 hrs = 15 degrees

  6. Seasonal Changes • Summer solstice: (near June 21st) most sunlight hours, “longest day”, sun reaches highest point in the sky • Winter solstice: (near December 21st), least daylight hours, “shortest day”, sun reaches lowest point in the sky

  7. Seasonal Changes • Equinoxes: 2 days in which day and night are equal in length • Vernal equinox: (March 21st) • Autumnal equinox: (September 21st)

  8. Long-Term Changes • Precession: movement of the Earth that takes 26,000 years, changes the direction that the Earth’s axis points • Tropical year: 365.242 days (we use this one in our calendars) • Sidereal year: 365.256 days • Why the difference? • Earth’s precession

  9. Measuring Earth • 200 BC • Greek philosopher Eratosthenes will calculate the circumference of Earth • He used the noon day sun in two different cities to calculate the angle of the sun in the sky • The angles were separated by about 7.2 degrees…1/50th of a circle. • So…he multipled the distance between the two cities by 50. • He got 24, 428 miles • The actual circumference is 24, 908 miles

More Related