moon and earth cycles (teach)

Cycles related to movement of objects in the solar system

By Moira Whitehouse PhDNASA

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.

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)


hours


= one year





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)


hours


= one year





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.

http://www.seed.slb.com/



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 sometime people might guess.

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.

http://esminfo.prenhall.com/science/geoanimations/animations/01_EarthSun_E2.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

Cycles Cause(s)


hours


= one year





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. Choose the present month and year. 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/phases_3_2011.htm

http://www.tutiempo.net/en/moon/phases_3_2011.htm

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

http://www.wisegorilla.com/


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.




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.




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).

http://www.moonconnection.com/blue_moon.phtml

Cycles Cause(s)


hours


= one year





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)


hours


= one year





In Review...

moon and earth cycles (teach)

Technology

atakes earth

relationshipbetween

sunone revolution

hoursyears earth revolving

sunexperiences day time

day andnight

yearseasons earths axis

earthone revolution