* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download DaysSeasnsYears
Survey
Document related concepts
Aquarius (constellation) wikipedia , lookup
Copernican heliocentrism wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Extraterrestrial skies wikipedia , lookup
Astronomical unit wikipedia , lookup
Comparative planetary science wikipedia , lookup
Geocentric model wikipedia , lookup
Astronomy on Mars wikipedia , lookup
Tropical year wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Transcript
Why do we have Days, Seasons, and Years? What on Earth is a day? • “The time it takes for the Earth (or any planet/moon) to make one complete rotation.” • 24 hours • Part of each 24-hour day is lighted (daytime), part is dark (night). • The length of daytime and nighttime varies depending on how the Earth is tilted. Earth Orbit (Revolution) The Earth orbits (revolves) around the sun once every 365 days. This is where our year comes from. In fact, for every planet a year is the time it takes to orbit it’s star one time. Our orbit is not a perfect circle. It is an ellipse. When do you think we are closer to the sun - in our summer our our winter? Summer: 152,000,000 Km Winter: 147,000,000 Km Earth’s Tilt Reason for the Seasons: The earth’s axis is always tilted at 23.5. When a hemi-sphere tilts towards the sun it gets more direct sunlight so it experiences warmer temperatures (summer). The opposite is true when the tilt is away from the sun (winter). http://www.windows.ucar.edu/earth/climate/images/seasons_lg.gif Spring - March 21st • Spring Equinox • First day of Spring • Equal length of daytime & nighttime • Sun directly over equator • Fall in southern hemisphere North Summer - June 21st • Summer Solstice • First day of Summer North • Longest daytime in N hemisphere • Longest nighttime in S hemisphere • Sun over Tropic of Cancer • Winter in southern hemisphere. • 24 hours of daytime above the Artic Circle & 24 hours of nighttime below the Antarctic Circle. Fall - September 22 • Fall/Autumnal Equinox North • First day of Fall • Equal length of daytime and nighttime • Sun directly over equator • Springtime in southern hemisphere. Winter - December 21 • Winter Solstice North • First day of Winter • Longest nighttime in N hemisphere • Longest daytime in S hemisphere • Sun over Tropic of Capricorn • 24 hours of nighttime above the Artic Circle & 24 hours of daytime below the • Antarctic Circle. Summer in southern hemisphere