Seasons Challenge

1. Seasons Challenge Created By: Allison Claroni, Jessica Geiger, Kasey Hemeon, Rayna Peirce, and Katie Donnelly Moran

2. Diagrams

3. Our Solar System

4. Earth’s Seasons • The reasons for Earth’s Seasons • The 23.5° tilt of the axis • The revolution around the sun • Seasons are not the same across Earth because the Sun’s rays hit the Earth’s surface at different angles and intensities

5. Aphelion and Perihelion • The aphelion is the spot on Earth's orbit that is farthest from the Sun.  It occurs on July fourth and the Earth is about 152 million km away from the Sun. • The perihelion is the spot on Earth's orbit that is closest to the Sun.  It occurs on January third and the Earth is about 147 million km away from the Sun. • The Sun isn't at the center of the Earth's orbit, but it's pretty central in relationship to the planets.  • Earth's orbit is ecliptic but almost a perfect circle • Thus the difference between its distance to the Sun at the aphelion and at the perihelion is slight.  • Seasons have nothing to do with the distance Earth is away from the Sun. • Summer, in the Northern Hemisphere, occurs when that part of the Earth is facing towards the Sun • Winter, in the Northern Hemisphere, occurs when that part of the Earth is facing away from the Sun.

6. Aphelion and PerihelionDiagrams Aphelion~ point of orbit where Earth is farthest from the Sun (July 4). The Earth is about 152 million km (roughly 96 million miles) from the Sun. Perihelion~ point of orbit where Earth is closest to the Sun (Jan. 3). The Earth is about 147 km (roughly 91 million miles) from the Sun.

7. Latitude Lines This diagram shows the approximate temperature of the Earth’s latitude lines in different months.  The darker the color the colder the temperature.  It can be concluded that it is warmer (summer) in the Northern Hemisphere (north of the Equator) in the months May to August.  However, in that same time frame, the part of the Earth south of the Equator is experiencing their coolest temperatures.  Since the Earth isn't perfectly straight up and down, this shows that the Northern Hemisphere is tilted toward the Sun in the months May to August, and tilted away from the Sun from September to April.

8. Daylight Lengths The reason the number of hours of daylight changes from day to day has to do with the fact that the Earth is either rotating a little closer or farther from the Sun each day. The rotation of Earth is influenced by its orbit around the Sun. The Sun moves mostly from east to west If it moves north to south, the change in daylight hours would rapidly change from day to day. Because the Sun moves from east to west, the change is very minor from day to day.

9. Daylight Lengths (continued) The length of daylight we have beginning on the Summer Solstice decreases by a minute or two everyday until the Winter Solstice when the Sun stays up shorter than it does any other day of the year (longest amount of dark.) The length of daylight we have beginning on the Winter Solstice increases everyday until the Summer Solstice when the Northern Hemisphere receives the most daylight of the year (shortest amount of dark.) On the 2 equinoxes, there is equal length of night and day (equinox means equal night) During the summer, in the Northern Hemisphere there is no daylight in the North Pole and there is no darkness in the South Pole During the winter, in the Northern Hemisphere there is no darkness in the North Pole and there is no daylight in the South Pole

10. Direct Sunlight Unobstructed Sunlight - The Earth’s axis is tilted in relation to the Sun, so when the Earth is tilted towards the Sun it will receive more direct sunlight then than it would when the Earth is tilted away from the Sun. - Earth is not always receiving direct sunlight. - The Northern Hemisphere receives more direct sunlight in the summer because that part of the Earth is tilted towards the Sun.  We receive more sunlight overall when Earth is experiencing summer and the more sunlight there is, the more direct sunlight Earth receives. - Plant growth is largely effected by direct sunlight. The more direct sunlight a plant receives, the faster it grows. So in the summer when the Northern Hemisphere receives a lot of direct sunlight, many plants grow. And in winter plants, we are receiving minimal direct sunlight so many plants die. -When a hemisphere is experiencing summer, it gets the most amount of direct sunlight it will get all year long. When a hemisphere is experiencing winter, it gets the least amount of direct sunlight it will get all year long.

11. The Sun’s Path Across the Sky The Sun is not at the same height in the sky over the year. This is due to the elliptical orbit of the Earth around the Sun and the tilt of the axis.

12. Angles of the Sun This diagram shows that the Sun appears in different places in the sky during different seasons.

13. Solar Noon • Solar noon is the time during the day that is exactly in the middle of the number of daylight hours for that day • Can be determined by calculating the length of daylight for that day and divide by two • When the Sun is at its highest point in the sky • Not always 12 o’clock noon • Your shadow will be at its shortest at this time • This time varies throughout the year

14. Solar or Sunlight Intensity • This is how scientists express brightness; when referring to solar intensity •  Radiation emitted from the Sun is about 8% ultra-violet, 44% visible light, and 48% infrared • Solar intensity is fairly constant on any given day of a year • A diagram of an example of solar intensity would look like a squared off "U" • The main influence is the length of atmosphere in which the Sun's rays must travel through to get to the atmosphere •  During the equinox at noon, on the Equator, the Sun is directly overhead and the its rays hit the Earth at a sharper angle and does not have to travel as far through the atmosphere to get to Earth.  So the further away a place is from the Equator means sunlight must travel a longer distance through the atmosphere to reach Earth's surface  • A major factor is geographical location; altitude/elevation

15. Solar Intensity Graph The Two Main Factors: 1) The length of the atmosphere in which the Sun's rays must travel through to get to Earth 2) The altitude or elevation of a certain place

16. Solar Intensity Diagrams

17. Declination Angle of the Sun in the Sky • Declination is a measurement of the angle between the Sun's rays and the Earth's equatorial plane. • It changes over the course of a year • The declination of... • -The Vernal Equinox is 0 • -The Summer Solstice is a maximum of 23.5 degrees • -The Autumnal Equinox is 0 • -The Winter Solstice is minimum of -23.5 degrees • See this chart for the declination of every day of the year: • http://www.wsanford.com/~wsanford/exo/sundials/DEC_Sun.html • During the Summer Solstice, a region of the Earth north of the Arctic Circle experiences 24 hours of sunlight that day. Therefore, Antarctica receives 24 hours of darkness that day. • If the Earth wasn't tilted on its axis when rotating, the declination would always be 0

18. The equation to determine the declination angle  where d is the day of the year with Jan 1 is d = 1

19. Analemma A definition of analemma is "A graduated scale in the shape of a figure eight, indicating the Sun's declination and the equation of time for every day of the year and usually found on sundials and globes."  Basically an analemma is a scale that will show how much the Sun's apparent path has changed throughout the year.  An analemma occurs because of the Earth's tilt and it's elliptical revolution.  If the Earth was not tilted, the Sun would always move in the same apparent path across the sky.  But since it is tilted, the Sun's position in the sky moves north and south.  If the Earth did not have an elliptical revolution but instead an orbit in the shape of a perfect circle, the Sun's position would only move north and south.  But since it has an elliptical revolution, its location in the sky moves east and west, as well as north and south.

20. Analemmas

21. Season Facts Go to seasons chart

22. Winter • In the Northern Hemisphere, winter starts when Earth’s axis is pointing directly away from the Sun • In the Northern Hemisphere, winter starts on Dec. 21 or 22 • Winter is also known as the Winter Solstice • Days become much shorter and nights become much longer • The weather is much colder and it snows • The Southern Hemisphere is experiencing summer

23. Spring • Neither the Northern or Southern Hemisphere receives direct sunlight on this special day • The first day of spring in the Northern Hemisphere is March 21 or 22 • The first day of spring is also known as the Vernal Equinox • The weather is much warmer than it was in the winter and it rains more frequently, especially in April • The Southern Hemisphere is experiencing autumn

24. Summer • In the Northern Hemisphere, summer starts when Earth’s axis is pointing directly towards the Sun • The first day of summer in the Northern Hemisphere is June 21 or 22 • The first day of summer is also known as the Summer Solstice • The weather is very hot and people often go to places outdoors like beaches to cool off and relax • The Southern Hemisphere is experiencing winter

25. Autumn • Neither the Northern or Southern Hemisphere receives direct sunlight on this special day • The first day of fall in the Northern Hemisphere is September 22 or 23 • The first day of autumn is also known as the Autumnal Equinox • It’s much windier, but fall is one of the most beautiful months when the leaves on the trees change colors • The Southern Hemisphere is experiencing spring

26. Comparing the Seasons

27. The Earth vs. The Sun  The Earth revolves around the Sun in an elliptical path.  However, the path is close to a perfect circle so the distance between the Earth does not vary too much, not enough to factor the seasons on the Earth. Scientists have figured out a pretty sufficient way to measure the distance between the earth and the sun. Click this link and scroll down to the bottom of the page to find out how! http://curious.astro.cornell.edu/question.php?number=400. This diagram shows the position of the sun in relationship to earth. It shows the rotational and revolutionary directions of the earth. It also shows the tangential force against and towards the direction of the rotational force. (NOT  DRAWN  TO  SCALE)

28. The Earth vs. The Sun (cont.) Also, due to Earth's precession, the Earth wobbles slightly as it orbits around the Sun. But it takes the Earth 23,000 years to actually complete one "wobble". The Earth's orbit also becomes slightly more oval, and then slightly less oval every 100,000 years. That change in the shape of the Earth's orbit is known as eccentricity. And, the tilt of the Earth becomes nearly three degrees different in relationship to the plane of its orbit every 41,000 years. Those three factors all influence a slight change of climate on Earth, as the amount of energy the Earth is receiving varies. That all causes global warming on Earth, so this isn't a very good thing that is happening to the Earth for quite a few reasons having to do with our environment.

29. The Earth vs. The Sun (cont.) Facts about Earth and Sun's relationship: Earth recieves almost ALL of it's energy by means of radiation from the Sun. The Sun also influences the climate changes of various locations on Earth at different times throughout the year.                                                                                                                 Earth completes one revolution around the Sun about every 365 days. The path in which Earth travels on is called an eliptical path. Earth rotates on a fixed plane. That plane is tilted 23.5 degrees with respect of its vertical axis as it rotates on its axis and revolves around the Sun. The Earth needs 23hrs 56mins to complete one full rotation on its axis. Earth's axis is always pointed in the same direction; toward the North Star. Earth rotates and revolves around the Sun counter clockwise from the North Pole.

30. Earth Reference Map

31. Glossary (page 1) Analemma: A graduated scale in the shape of a figure eight, indicating the Sun's declination and the equation of time for every day of the year and usually found on sundials and globes. Autumnal Equinox: time of the year (September 22nd-23rd) at the end of summer when day and night are of equal length; beginning of autumn in the Northern Hemisphere. Axis: imaginary vertical line through the center of a body around which the body rotate, spins Declination: the angular distance of a heavenly body from the celestial equator, measured on the great circle passing through the celestial pole and the body. Equinox: the time when the Sun crosses the plane of the earth's equator, making night and day of approximately equal length all over the Earth. Geosynchronous orbit: orbit in which a satellite’s rate of evolution exactly matches the Earth's rate of rotation Globe: spherical, or round, model of the world. Hemisphere: northern or southern half of the Earth. International dateline: line located along the 180th meridian; where the line is crossed going west, one day is added; when it is crossed going east, one day is subtracted.

32. Glossary (page 2) Overhead Sun: when the Sun is directly overhead a certain place on Earth. At this time, the Earth's surface and the midday Sun form a 90 degree angle. This line of latitude receiving "overhead sun" is also known as the line of latitude that receives the most direct sunlight. Summer Solstice: time of year at the end of spring when there is the most amount of daylight and least amount of darkness in a day; the solstice which takes place on June 21st-22nd that marks the beginning or summer in the Northern Hemisphere. Tangential Force: a force which acts on a moving  body in the direction of a tangent to the path of the body, its effect being to increase or diminish the  velocity; - extinguished from a normal force, which acts at right angles to the tangent and changes the direction of the motion without changing the velocity. Velocity: the time rate of change of position of a body in a specified direction. Vernal Equinox: time of year (March 21st-22nd) at end of winter when day and night are of equal length; beginning of spring in the Northern Hemisphere. Winter Solstice: time of year at the end of fall when there is the least amount of daylight and most amount of darkness in a day; the solstice that takes place on December 21st-22nd that marks the beginning of winter in the Northern Hemisphere.

33. Youtube Videos • http://www.youtube.com/watch?v=EzEAnYQISno • http://www.youtube.com/watch?v=taHTA7S_JGk • http://www.youtube.com/watch?v=DuiQvPLWziQ • Bill Nye the Science Guy Video Links http://www.youtube.com/watch?v=YUrxRhQYdO4&feature=related http://www.youtube.com/watch?v=xRL_LC2EYW4 http://www.youtube.com/watch?v=brVdRsKCGaU

34. THE END