The Sun-Earth-Moon System Grade 6 Image Credit: wordpress.com

Content Topics Associate cycles in the sky with time Describe why Earth has seasons Determine the phase of the moon Compare and contrast all types of eclipses

What are the motions of the Earth, Moon, and Sun? The apparent motion in the sky is due to the motions of the Earth and Moon. Image Credit: Ashish Meshram

Some Vocabulary Revolution is the action by a celestial body of going round in an orbit or elliptical course. The Moon revolves around the Earth Rotate is to turn around in a circle; to spin. The Earth rotates on its axis once each day.

From a Million Miles Away, NASA Camera Shows Moon Crossing Face of Earth

Practice How many rotations does Earth complete in one revolution? 364.2422 Do you think the Sun rotates and/or revolves? The Sun rotates an average of once every 25 Earth days. The Sun revolves once every 250 million years.

What are the cycles that determine time keeping? Many early calendars were based on the cycles of Moon phases. We currently use the Gregorian calendar (1582), based on the cycle of Earth’s revolution around the Sun. Leap years must be divisible by 4 Leap years exclude years divisible by 100

Solar Year Time taken to make one revolution around the Sun Time it takes Earth to complete a full orbit Time it takes the Sun to return to the same position in the cycle of seasons, as seen from Earth

Animation of a Year https://www.youtube.com/watch?v=_QcgDiF1a14

Slideplayer.com

Month The month is based on the motion of the Moon. Unit of time based on the revolution of the Moon around the Earth (27.3 days) and defined as the period between two successive new moons or, on average, 29.53 days.

Image Credit: wordpress.com

Practice Why does the moon phase cycle take longer than the moon orbit cycle? The Earth is traveling in its orbit while the Moon orbits the Earth. The Moon completes its orbit in 27.3 days. What is the change in position of the moon (number of degrees) in the sky, each day? 360 degrees = 13.2 degrees per day 27.3 days

Solar Day The day is based on the rotation of the Earth. The solar day is defined as the time it takes for the Sun to return to its culmination point (its highest point in the sky). Time for two successive crossings of the Meridian by our Sun.

Your Meridian Image Credit: astronomy.ohio-state.edu

Practice How many months are there in a year? How many hours are there in a day? 24 hours

What causes Earth to have Seasons? The changing distance between the Earth and the Sun is not the cause of the seasons. Our distance from the Sun only varies by 2-3% NASA Image

Tilted Earth 23.5° Tilt

Image Credit: lumenlearning.com Angled Sunlight The more direct sunlight a hemisphere receives, the more it is heated. Direct Sunlight Indirect Sunlight Image Credit: lumenlearning.com

lumenlearning.com http://astro.unl.edu/classaction/animations/coordsmotion/eclipticsimulator.html

Seasons and Sun Path Image Credit: pinterest

Practice Why is the number of daylight hours on the first day of fall and spring the same? The Sun’s position in the sky is the same on the first day of fall and spring. How can we know when it has been a year? Is there more than one way to tell? When it is Christmas When it is summer break When we have had all of the seasons

Why do we see different shapes of the Moon? As the amount of reflected sunlight that we can see changes, we see the phases of the Moon. Image Credit: hyperphysics.com

Moon Phase Terminology New Moon Phase – No illumination Full Moon Phase – All illumination 1st and 3rd Quarter – Half Gibbous – More than half Crescent – Less than half Waxing –Increasing Waning – Decreasing Image Credit: NASA

Practice There is always half of the Moon’s sphere reflecting sunlight. (True or False) True Is the moon ever visible during the day? Yes

More Practice If the moon in the image has been increasing in size each night, what is the phase of the moon? Waxing Gibbous http://astro.unl.edu/naap/lps/animations/lps.swf Image Credit: NASA

When do eclipses occur? Eclipses only occur when the Earth, Moon, and Sun all lie in the same plane (the ecliptic) and are in the same location of space at the same time. Image Credit: Wikipedia.org

Practice How often is it possible for an eclipse to occur? Every 6 months How can the tiny moon and Earth block the huge sun? Relative distance Image Credit: pinterest

Eclipse Terminology An eclipse is a shadow. Umbra: complete shadow Penumbra: partial shadow 2017 Eclipse Umbra Viewed from Space (NASA)

Total Solar Eclipse The umbra of the Moon's shadow touches Earth’s surface. Full disk of Sun is blocked. (Sun-Moon-Earth) Image Credit: NASA

Path of Totality The umbra from a total solar eclipse is at most 167 miles wide. Image Credit: http://www.eclipse2017.org/2017/maps.htm

Annular Solar Eclipse The umbra does not reach Earth, anti-umbra touches Earth. Sketch not to scale Image Credit: NASA

Partial Solar Eclipse The penumbra touches Earth, and part of Sun disk is blocked by Moon. Image Credit: lumenlearning.com

Practice What is the phase of our Moon during a total solar eclipse? New Moon Sketch a model of a total solar eclipse that shows the umbra and penumbra.

Lunar Eclipses The umbra of Earth's shadow covers our Moon. Image Credit: socratic.org

Partial Lunar Eclipse Image Credit: lumenlearning.com

Refraction The fully eclipsed Moon appears red because light is refracted in the Earth’s atmosphere. https://www.youtube.com/watch?v=UfxYHvlav5A

Practice What is the phase of the Moon during a total lunar eclipse? Full Moon Why is the shadow dark before it is red during a total lunar eclipse? The Earth must block most of the intense white light before the refracted red light can be seen. Sketch a model of a total lunar eclipse that shows the umbra and penumbra.