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This is a long slide show, could be used for a week or more's lesson. Does tie it all up nicely.
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Cycles related to the movement of objects in
the Solar System
By Moira Whitehouse PhD
On Earth we notice some cycles that occur at regular intervals.
Some of these cycles are day and night, years, seasons, moon phases and tides.
These cycles are determined by how the Earth, the Sun and the Moon move relative to one another in space.
The Earth moves around (orbits) the Sun.At the same time as the Earth is revolving around the Sun, the Moon moves around (orbits) the Earth.
As the Earth and Moon are orbiting, they are also spinning around (rotating) on an imaginary axis.
Earth rotating.
These movements result in the cycles of day and night, years, seasons, moon phases and tides.
Cycles (Effect) Cause(s)
Day and night Earth rotating one rotation=one day or 24
hours
Years Earth revolving or orbiting the Sun One revolution or one orbit
= one year
Seasons Earth’s axis on a tilt and Earth orbiting the SunOne revolution= 4 seasons summer, fall, winter, spring
Moon phases Moon orbiting the EarthOne revolution=8 moon
phases Tides Moon’s gravity pulling on the Earth’s oceans
Two high tides and two low tides every day
Why do we have day and night?
We have night because there is no sun light on our side of the planet.
We have day because there is sun light on our side of the planet.
http://starchild.gsfc.nasa.govNight time
Day time
Sunlight Sunlight
The side of the Earth facing the Sun experiences day time.
The side of the Earth facing away from the Sun experiences night time.
As the Earth circles the sun it also rotates on it axis (an imaginary line passing through the North and South poles).
http://sos.noaa.gov/
The other half is in shadow, the sun is not visible and it is dark. In that half it is night time.
As it rotates only half of the Earth at a time is in the sun light. In that half it is day time.
The Earth’s rotation causes every part of the earth to have both day and night time.
Our clocks and calendars are based on one day being 24 hours long. As can be seen bythis diagram, that’s about how it takes for the Earth to make one rotation on its axis.
Sunrise coming to the Horn of Africa
Cycles Cause(s)
Day and night Earth rotating one rotation=one day or 24
hours
Years Earth revolving or orbiting the Sun One revolution or one orbit
= one year
Seasons Earth’s axis on a tilt and Earth orbiting the SunOne revolution= 4 seasons summer, fall, winter, spring
Moon phases Moon orbiting the EarthOne revolution=8 moon
phases Tides Moon’s gravity pulling on the Earth’s oceans
Two high tides and two low tides every day
How is our year based on the relationship between Earth and Sun?
Years: Earth revolving or orbiting the Sun One revolution or one orbit = one
year
While rotating on its axis every day, the Earth is also making a very long trip revolving around (or orbiting) the Sun.
The amount of time it takes for the Earth to make one complete revolution around the Sun is one year or 365 ¼ days.
Every four years we have leap year in which we add one day to the calendar to make up for the four one-fourth days.
One trip (oribt) around the Sun (point A back to point A) takes Earth one year of travel time. That is how people came up with the idea to measure time in years.
A
Cycles Cause(s)
Day and night Earth rotating one rotation=one day or 24
hours
Years Earth revolving or orbiting the Sun One revolution or one orbit
= one year
Seasons Earth’s axis on a tilt and Earth orbiting the SunOne revolution= 4 seasons summer, fall, winter, spring
Moon phases Moon orbiting the EarthOne revolution=8 moon
phases Tides Moon’s gravity pulling on the Earth’s oceans
Two high tides and two low tides every day
Why is the weather different at different times of the year? Why do we have seasons?
Seasons: Earth’s axis on a tilt and Earth orbiting
the SunOne revolution=
4 seasons summer, fall,
winter, spring
Seasons
Parmetheon planet
We will look at the two reasons for seasons:
1. The Earth orbiting the Sun
2. The tilt of the Earth on its axis as it orbits the Sun
Without this there would be no seasons, but there would also be nothing else.
Is the reason we have seasons, as we will see.
If the Earth’s axis were straight up and down as shown in this picture, there would be no seasons. Weather, yes, but no seasonal patterns.
But it is not, it is tilted as shown in this picture. And now we shall see how that causes the seasons.
Just how much is the Earth tilted?
The axis of the Earth is tilted 23.5 degrees.
Wikipedia Commons
North Star
The northern axis of the Earth happens to point within one degree to Polaris, a fairly bright star we call the North Star.
23.5º
Because of the tilt of the earth, during certain positions in its orbit of the Sun the Earth’s Northern Hemisphere is tilted toward the sun; and six months later and on the opposite side of the orbit, the Southern Hemisphere is tilted toward the sun.
Southern Hemisphere tilted towards the Sun
Northern Hemisphere tilted towards the Sun
http://www.seed.slb.com/ Permission is granted to make copies of this document for educational purposes only.
Summer
Summer
SummerSummer
Fall
Winter
Spring
Or, from another view point
http://www.seed.slb.com/ Permission is granted to make copies of this document for educational purposes only.http://www.seed.slb.com/ Permission is granted to make copies of this document for educational purposes only.
A given amount of heat energy must cover a greater amount of space (and is therefore weaker) the further it is from the equator when it strikes the earth.
It is actually how direct the sun’s rays strike the Earth that determines seasonal temperatures.
We can see that in the warmer “summer” months, the Earth is not closer to the sun as people often think.
Lower latitudes near the earth’s equator, therefore, receive a greater concentration of incoming energy and are warmer than higher latitudes.
As seen here, the sun’s incoming energy (we will call it four units) is more concentrated and covers a smaller circle nearer the equator than the same four units covering a much larger circle closer to the poles.
http://esminfo.prenhall.com/science/geoanimations/animations/01_EarthSun_E2.html
This animated visual shows the Earth moving in orbit through the seasons.
Another animation showing the Earth moving in orbit through the seasons. Look through the list and choose “Seasons Interactive”.
http://highered.mcgraw-hill.com/sites/0072482621/student_view0/interactives.html#
http://www.srh.noaa.govhttp://www.srh.noaa.gov
Winter in the Northern Hemisphere
Summer in the Northern Hemisphere
Summer in the Southern Hemisphere
Winter in the Southern Hemisphere
Fall in the Northern Hemisphere
Spring in the Northern Hemisphere
Spring in the Southern Hemisphere
Fall in the SouthernHemisphere
An animation showing the day and night, years and seasons. Under “Earth and Beyond” choose “The Earth”.
http://www.engineeringinteract.org/resources.htm
Cycles Cause(s)
Day and night Earth rotating one rotation=one day or 24
hours
Years Earth revolving or orbiting the Sun One revolution or one orbit
= one year
Seasons Earth’s axis on a tilt and Earth orbiting the SunOne revolution= 4 seasons summer, fall, winter, spring
Moon phases Moon orbiting the EarthOne revolution=8 moon
phases Tides Moon’s gravity pulling on the Earth’s oceans
Two high tides and two low tides every day
Phases of the Moon
The Moon goes through these phases because: 1) the Moon is revolving around the Earth, and 2) the Moon is reflecting sunlight towards the Earth.
What causes the Moon's phases?
Half of the Moon is always lit, not just the portion we see: however, sometimes we only see the lit portion of the Moon based on where it is in its orbit.
Before an in-depth study of the Moon’s phases, we will look at the Moon’s relationship with the Earth.
NASA
The moon rotates on its axis as it orbits the Earth.
Moon orbits the Earth
Earth orbits the Sun
Earth’s axis
At the same time as the Earth is rotating and orbiting (revolving around) the Sun, the Moon is rotating and orbiting the Earth.
There are eight phases that the moon goes through and they always occur in the same order.
The Sun's light seems to move from right to left across the surface of the Moon.
Now to that “in-depth” look at the phases of the Moon.
The phases of the Moon are: 1) New Moon,2) Waxing Crescent3) First Quarter, 4) Waxing Gibbous 5) Full Moon, 6) Waning Gibbous7) Last Quarter 8) Waning Crescent
And back to the New Moon.
New Moon
Waxing Crescent
First Quarter
ThirdQuarter
WaxingGibbous
WaningGibbous
FullMoon
Waning Crescent
New Moon
Let’s look at the phases of the moon on a calendar for November, 2009. Notice that the change from phase to phase is very gradual and takes about a month for the cycle.
http://www.tutiempo.net/en/moon/
http://www.valdosta.edu/~cbarnbau/astro_demos/frameset_moon.html
Select Moon Phases in the following URL for an outstanding animation of the Moon and its phases.
As shown in the diagram, the new moon occurs when the moon is positioned between the earth and sun. The entire illuminated (lit up) side of the moon is on the back part of the moon– the half that we cannot see.
http://www.wisegorilla.com free clip art for educational use
At a full moon, the earth, moon, and sun are in approximately lined up, just as the new moon, but this time the moon is on the opposite side of the earth. As a result, the entire sunlit part of the moon is facing us. The shadowed portionis entirely hidden from view.
http://www.wisegorilla.com free clip art for educational use
The first quarter and third quarter moons (both often called a "half moon"), occur when the moon is at a 90 degree angle with respect to the Earth and Sun. So we are seeing exactly half of the Moon illuminated andhalf in shadow.
http://www.wisegorilla.com free clip art for educational use
When a calendar month has two full moons, the second full moon is called a blue moon. (i.e. the expression once in a blue moon.)
It takes for the Moon 29.5 days to orbit the Earth, about one month. (Also the amount of time from one new moon to the next).
Cycles Cause(s)
Day and night Earth rotating one rotation=one day or 24
hours
Years Earth revolving or orbiting the Sun One revolution or one orbit
= one year
Seasons Earth’s axis on a tilt and Earth orbiting the SunOne revolution= 4 seasons summer, fall, winter, spring
Moon phases Moon orbiting the EarthOne revolution=8 moon
phases Tides Moon’s gravity pulling on the Earth’s oceans
Two high tides and two low tides every day
What causes tides in the ocean?
The Moon’s gravity pulling on the Earth causes the tides.
To understand Moon tides we must have some idea about gravity.Gravity is a force.Gravity is a force that pulls.
Every object has gravity.So every object pulls on every other object.
The more mass an object has, the harder it pulls.
We will use two hypothetical planets for our example. Both the blue and green planets are pulling on each other.
Which one pulls harder?
This should help us see that the more mass an object has the stronger its gravity.
The Earth obviously has more mass than the Moon and it pulls harder. So much harder that the Moon is held in an orbit around the Earth as though by some magically strong string.
But the Moon’s gravity is also pulling on the Earth. So hard that the oceans swell toward the Moon where ever it passes. We call this high tide.
EarthMoon
Hopewell rocks at at low and high tides.
Ocean tides are caused by the gravity of the moon pulling on the ocean’s water.
As a result of this pull of gravity, the ocean’s water bulges toward the Moon on every rotation of the Earth. This bulge is called high tide and it occurs about every 12 hours—twice a day. Low tide occurs between high tides.
The point is, because of the Moon’s gravity, the ocean’s water bulges toward the Moon on every rotation of the Earth.
Sun
Would the tides be greater if the Sun and Moon were lined up? Why?
http://www.valdosta.edu/~cbarnbau/astro_demos/frameset_moon.html`
Open this website and choose tides.All good, but these two especially important for understanding tides.
Cycles Cause(s)
Day and night Earth rotating one rotation=one day or 24
hours
Years Earth revolving or orbiting the Sun One revolution or one orbit
= one year
Seasons Earth’s axis on a tilt and Earth orbiting the SunOne revolution= 4 seasons summer, fall, winter, spring
Moon phases Moon orbiting the EarthOne revolution=8 moon
phases Tides Moon’s gravity pulling on the Earth’s oceans
Two high tides and two low tides every day
In Review...