Transcript seasons power point

Seasons
Challenge
Created By:
Allison Claroni, Jessica Geiger,
Kasey Hemeon, Rayna Peirce, and
Katie Donnelly Moran
Diagrams
Our Solar System
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
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.
Aphelion and Perihelion
Diagrams
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.
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.
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.
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
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.
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.
Angles of the Sun
This diagram shows that
the Sun appears in
different places in the
sky during different
seasons.
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
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
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
Solar Intensity Diagrams
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
The equation to determine the
declination angle
where d is the day of the year with Jan 1 is d = 1
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.
Analemmas
Season Facts
Go to
seasons
chart
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
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
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
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
Comparing the Seasons
(referring to the
Northern
Hemisphere)
Winter
Spring
Summer
Autumn
Official Name
Winter Solstice
Vernal Equinox
Summer
Solstice
Autumnal
Equinox
Line of Latitude
Receiving the
Most Direct
Sunlight
Tropic of
Capricorn
Equator
Tropic of
Cancer
Equator
Hemisphere
Receiving the
Most Direct
Sunlight
Northern
Hemisphere
Neither
Southern
Hemisphere
Neither
December 21 or
22
March 21 or 22
June 21 or 22
September 22
or 23
Starting Date
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)
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.
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.
Earth Reference Map
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.
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.
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
THE END