Performance Benchmark E.8.B.7
Students know regular and predictable motions of Earth around the Sun and the Moon around
Earth explain such phenomena as the day, the year, phases of the Moon, and eclipses. E/S
“Son, I can’t wait to take you up to the observatory, there will be another lunar eclipse in two
days,” Wendy, an astrophysicist with NASA says. “Wow, really I can’t wait, wasn’t there a lunar
eclipse not too long, ago?” asks her son, Gordon. “Yes, there was last year, but it was a total
solar eclipse. Remember we had to wear special glasses to view it?” “Oh, yeah, I can’t wait to go
up there with you!”
Scientists, astrophysicists, and astronomers have an important job of predicting the cycles of the
seasons, moon phases, and eclipses for research, education and enthusiasts, alike. It can be an
exciting experience to be able to view an eclipse, or even a blue moon in your lifetime. Scientists
can predict the change of seasons, moon phases and when an eclipse will occur because they
occur in cyclical patterns, which are calculated, predicted and observed by the scientific
community.
Earth
Earth, a small planet in a vast universe, is the third planet from the Sun in the Solar System.
Earth is a unique planet in the Solar System, in that it supports life. The atmosphere of Earth
protects the surface from extreme high and low temperatures, allowing life to flourish. Animals,
plants, fungi, bacteria, and protists compose the life that is thriving on Earth’s continents and in
its oceans. Earth, known as the “Blue Marble”, due to the fact that approximately 75% of Earth’s
surface being covered in water, while rocky continents of diverse physiographic regions, create
the remaining quarter of Earth’s surface.
Though Earth is a small planet in the Solar System, it ranks as the fifth largest planet, with a
diameter of about 8,000 miles (13,000 km). Pluto, the smallest planet (now classified as a dwarf
planet) in the Solar System, is one-fifth the size of Earth, while Jupiter, the largest planet, has a
diameter approximately 11 times larger than Earth. Although Earth appears round in most
pictures, it is in fact not round due to its rotation. Earth is an oblate spheroid, with an equatorial
diameter that is slightly larger than at the poles. The diameter of Earth at the equator is 7,926.41
miles, whereas from the North to South Pole, Earth’s diameter is 7,899.83 miles (12,713.54), a
difference of 26.58 miles (42.78 kilometers). This slight difference creates a bulge at the equator,
creating an imperfect sphere.
Figure 1. Earth is known as the “Blue Marble”, due to the vast oceans covering its surface.
(From http://www.rps.psu.edu/probing/graphics/earth2.jpg)
Rotation
Earth spins on an imaginary line, which runs from the North Pole to the South Pole, called its
axis. The rotation of Earth, when viewed from above the North Pole is in a counter-clockwise
direction, and this rotation causes day and night on Earth. The period of rotation of Earth is
approximately 24 hours, which is known as a solar day. A sidereal day is when Earth rotates to
the same position to face the same stars in the sky and this takes 23 hours and 56 minutes. The
difference between a solar day and sidereal day is 4 minutes, which means a viewer will see the
same stars rise above Earth’s horizon four minutes earlier each day.
Figure 2. A sidereal day lasts 23 hours and 56 minutes, whereas a solar day lasts 24 hours.
Our calendar is based on a solar day.
(From http://www.physics.hku.hk/~nature/CD/regular_e/lectures/images/chap02/day.jpg)
To view an excellent animation of Earth’s rotation and a sidereal day, go to
http://www.edumedia-sciences.com/a241_l2-solar-day.html
Revolution
Earth orbits the Sun, the center of our Solar System, in a path called a revolution. Earth revolves
around the Sun at a speed of 66,700 miles (107,000 kilometers) an hour, or 18.5 miles per
second. Earth’s revolution around the Sun takes 365 days 6 hours 9 minutes 9.54 seconds to
travel 584 million miles around the Sun, which is known as a sidereal year. On Earth, humans
use a calendar year, which is usually 365 days long, leaving 6 hours 9 minutes and 9.54 seconds,
remaining each year to accumulate. To maintain alignment with the beginning dates of seasons, a
leap year occurs every four years to keep seasons beginning on the same date each year. During a
leap year, an extra day is added to the shortest month of the year, February, yielding 29 days.
Figure 3. A solar year occurs when Earth revolves around the Sun.
(From http://www.hort.purdue.edu/newcrop/tropical/lecture_02/01m.jpg)
Seasons
Earth is tilted 23.5 degrees from the plan of the ecliptic, which creates differing amounts of
incoming solar radiation (insolation) to reach Earth’s surface as the Earth progresses in its orbit
around the Sun. In the Northern Hemisphere, Earth experiences winter when this hemisphere is
tilted away from the Sun, resulting in indirect insolation. When, Earth moves through its orbit
and approaches summer, the Northern Hemisphere of Earth is tilted towards the Sun, causing
more direct insolation to reach Earth’s surface. The start of Fall and Spring are known as the
Autumnal Equinox and Vernal Equinox, respectively, they occur when Earth experiences exactly
12 hours of daylight and 12 hours of night.
The distance of Earth to the Sun doesn’t create seasons on Earth; in fact Earth is actually closer
to the Sun when it is winter in the northern hemisphere than during the summer in the northern
hemisphere. In winter, the distance of Earth to the Sun is 91.4 million miles (147.1 million
kilometers), whereas during the summer it is 94.5 million miles (152.1 million kilometers). The
seasons are due to the tilt of the Earth.
To view a flash animation of Earth, Moon and Sun revolution relationship, go to
http://www.edumedia-sciences.com/a520_l2-sun-earth-moon.html
Figure 4. Earth’s axial tilt of 23.5 degrees causes seasons on Earth as it revolves around the Sun.
(From http://www.metoffice.gov.uk/corporate/pressoffice/2006/images/pr20060317b_a.gif)
Figure 5. The angle of insolation and duration of daytime heating creates seasons on Earth.
(From http://www.astro.virginia.edu/class/oconnell/astr121/im/hours-of-daylight-v-date.jpg)
Moon Phases
The Moon is Earth’s only natural satellite. The rocky surface of the Moon is lit by the Sun as it
rotates on its axis in its revolution around Earth. Observers of the Moon can view lit portions of
the Moon throughout its revolution period of 27.3 days; these lit portions are known as Moon
phases. The Moon phases as viewed from Earth are: 1. New Moon, 2. Waxing Crescent, 3. First
Quarter, 4. Waxing Gibbous, 5. Full Moon, 6. Waning Gibbous, 7. Last Quarter, and 8. Waning
Crescent. As the Moon moves between Earth and the Sun, an unlit portion of the Moon faces
Earth, this is known as the New Moon phase. In this phase, the Moon is waxing, which means an
observer can view more of the lit portion of the Moon with each passing day. As a portion of the
moon becomes lit, the Moon is said to be a Waxing Crescent, this means that the lit portion is
getting larger and larger. After about seven days, the lit portion of the Crescent Moon has grown
to the point that half of the visible moon is lit. The Moon is approaching the First Quarter phase,
where an observer can view one-quarter of the Moon being lit by the Sun. This is where the
naming of the phases becomes tricky, at any given moment an observer on Earth can only see a
maximum of half the moon, the other half is never visible as it is always facing away from the
Earth. So when the moon is in its First Quarter phase, an earth-bound observer see’s half of the
visible portion of the moon being lit by the sun. Despite the fact that half the moon appears to be
lit, it truly is only a quarter of the moon that is lit and visible from Earth, hence the name, First
Quarter. Over the next seven days the lit portion of the moon continues to “wax” or grow. The
moon is said to be Waxing Gibbous during this time. Gibbous refers to the bulbous shape kind
of like the belly of a pregnant woman, as time passes it gets more and more rounded. At
approximately 14 days after the New Moon, the entire face of the moon, that is visible from the
Earth, is now lit. The Moon is said to be in the Full Moon phase. As the Moon continues its orbit
around Earth, observers experience the waning of the Moon, where observers view less of the
Moon’s lit surface. Over the next seven days, the Moon passes through the Waning Gibbous
phase until it reaches the Last Quarter phase, where, again one-quarter is lit by sunlight. Over the
next seven days, the moon passes through the Waning Crescent phase where the visible portion
of the moon gets smaller and smaller unlit portion of the Moon reaches its original New Moon
position, where observers would not see any lit portion of the Moon.
Figure 6. Moon phases are observed on Earth as the Moon revolves around Earth.
(From http://www.moonconnection.com/images/moon_phases_diagram.jpg)
To view a moon phase calendar, go to
http://stardate.org/nightsky/moon/
Eclipses
Eclipses are a result of the interaction of the revolutions of Earth, Moon and Sun. Two types of
eclipses can occur, Solar and Lunar. A Solar eclipse is when the Moon casts a shadow on Earth,
as a result of the Moon being in between Earth and the Sun and can only occur during the New
Moon Phase. A Lunar eclipse, which can only occur when the moon is in a Full Moon phase,
occurs when the Moon is in the shadow, or umbra of the Earth. Solar and Lunar eclipses can be
either partial or total eclipses, depending on whether the light from the sun is partially or entirely
blocked. Depending on your location on Earth, you may experience a solar or lunar eclipse in
your lifetime.
Figure 7. A total solar eclipse occurs when the Moon blocks out the view of the Sun for observers on Earth.
(From http://www.windows.ucar.edu/sun/images/eclipse_dia_big.jpg)
Figure 8. A lunar eclipse occurs when the Moon passes through the shadow cast by Earth.
(From http://www.sky-watch.com/skytour/lunar_eclipse_diagram.jpg)
To view an eclipse schedule and geographic location to view an eclipse, go to
http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html
Performance Benchmark E.8.B.7
Students know regular and predictable motions of Earth around the Sun and the Moon around
Earth explain such phenomena as the day, the year, phases of the Moon, and eclipses. E/S
Common misconceptions associated with this benchmark
1. Students have difficulty understanding Earth’s rotation is responsible for day and
night.
Earth’s rotation on its axis causes humans to experience day and night. As Earth rotates 360°
in one day, an observer on Earth would experience daylight when the sun rises on the
observer’s location and the observer would experience night when the sun appears to set over
the observer’s horizon. Students have trouble visualizing themselves at a fixed position on
the globe as their location experiences sunrises, the sun overhead and sunsets. What is
actually occurring is Earth rotating and the sun appears to move across the sky.
An excellent model and animation of Earth’s rotation is located at
http://www.onr.navy.mil/focus/spacesciences/observingsky/motion1.htm
A tutorial complete with an animated model of Earth’s rotation can be viewed, at
http://www.windows.ucar.edu/tour/link=/the_universe/uts/earth2.html
2. Students have difficulty with understanding that Earth’s distance to the Sun is not
responsible for the seasons.
A common misconception when describing Earth’s motion in space is the fact that Earth’s tilt
on its axis is the primary reason Earth experiences seasons. Students have difficulty
understanding that Earth is actually closer to the Sun in winter than it is during summer.
Therefore, the Northern Hemisphere will experience an increase in direct insolation as Earth
moves from its winter position to its summer position in its orbital path. An increase in direct
insolation causes higher surface temperatures for Earth’s Northern Hemisphere.
To view a model and animation of Earth’s revolution, go to
http://esminfo.prenhall.com/science/geoanimations/animations/01_EarthSun_E2.html
To view an informative narrated animation of Earth’s seasons and insolation, go to
http://www.eram.k12.ny.us/education/components/docmgr/default.php?sectiondetailid=1750
0&fileitem=4750&catfilter=452
3. Students have difficulty understanding apparent diameter of planets and moons.
A common misconception develops among students when teaching about solar and lunar
eclipses. A solar eclipse will occur when an observer on Earth views the moon blocking out
the view of the sun. Some students wonder how this could occur because of the significant
size difference of Earth’s Moon and the Sun. The reason that this occurs is the result of the
apparent diameter of the Moon to observers on Earth. Basically, the Moon looks bigger than
it is because it is closer than the Sun to the observer. It is similar to sitting on the couch while
watching a large wide screen television, and someone walks directly in front of you blocking
your view of the television. It is not a result of them being wider than the television, but their
body width is apparently larger than the television.
To view a diagram which models the alignment of a solar eclipse, go to
http://encyclozine.com/Astronomy/NotesImages/Topic53NotesImage1.gif
To view a schedule that displays sunrise, sunset of the Sun and Moon for your location on
Earth, go to
http://aa.usno.navy.mil/data/docs/RS_OneDay.php
4. Students inaccurately believe that the Moon phases are a result of Earth’s shadow on
the Moon.
This is a common misconception when discussing Moon phases with students. The Moon
revolves around Earth in a period of 27.3 days and an observer on Earth would view different
parts of the Moon lit up by sunlight. The different parts of the Moon lit up are called phases,
and an observer can view a different phase approximately every three to four days.
To view a list of common Moon misconceptions and teaching strategies intended to change
the learner’s model of Moon phases, go to
http://www.lpi.usra.edu/education/score/public_understanding/misconceptions.shtml
To see an overview of an excellent Oreo cookie Moon Phase activity, go to
http://analyzer.depaul.edu/paperplate/Oreo%20Moon%20Phases.htm
To view a calendar which provides the Moon Phase for any particular day, go to
http://stardate.org/nightsky/moon/
Performance Benchmark E.8.B.7
Students know regular and predictable motions of Earth around the Sun and the Moon around
Earth explain such phenomena as the day, the year, phases of the Moon, and eclipses. E/S
Sample Test Questions
Questions and Answers to follow on a separate document
Performance Benchmark E.8.B.7
Students know regular and predictable motions of Earth around the Sun and the Moon around
Earth explain such phenomena as the day, the year, phases of the Moon, and eclipses. E/S
Answers to Sample Test Questions
Questions and Answers to follow on a separate document
Performance Benchmark E.8.B.7
Students know regular and predictable motions of Earth around the Sun and the Moon around
Earth explain such phenomena as the day, the year, phases of the Moon, and eclipses. E/S
Intervention Strategies and Resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. Earth in Space Demonstration
This narrated animation using provides viewers with a clear and concise example of the
following concepts: rotation, revolution, moon phases and the seasons. It is an excellent
resource to use for all students regardless of their developmental level. Use the pause button
to take time to probe student knowledge with challenging questions, or simply have students
summarize Earth in Space movements.
To access this animation, go to
http://www.collinseducation.com/resources/ict%20activity/earth_FULL.swf
2. Observing Seasons and Summer and Winter Sunlight
From Harvard University, this is a valued website by several reputable reviewers for
providing an excellent guide for teaching Sun and season activities using hands-on science.
The site provides clear explanations, diagrams and inquiry based questions to use throughout
investigations. Some investigation titles include “Angle Spreads Sunlight, Tracking Sunrise
and Sunset Times, and Measuring Earth’s Tilt.”
To access this hands-on guide, go to
http://hea-www.harvard.edu/ECT/the_book/Chap2/Chapter2.html
3. Moon Phases with Oreos
An excellent activity for all ages, this website provides an instruction guide, template and a
section provided to use to challenge students with learning Moon phases. It is an excellent
way to challenge your students to create an inquiry based activity on Moon phases.
Incorporate technology and have students create a movie or slideshow depicting the Moon
phases using a digital camcorder or camera.
To access this lesson and template, go to
http://analyzer.depaul.edu/paperplate/Oreo%20Moon%20Phases.htm
4. Lunar and Planetary Institute -Moon Phases and Seasons Misconceptions and
Strategies
An invaluable resource, this website lists the most common misconceptions the public holds
about Earth, Sun and Moon relationships. This is an excellent website to prepare you prior to
teaching this topic. Use the links to develop strategies to change students’ misconceptions
about the movements of Earth, Sun and Moon.
To access this invaluable resource, go to
http://www.lpi.usra.edu/education/score/public_understanding/misconceptions.shtml
5. Earth in Space – Big Kid Science
This is an excellent tutorial that provides three separate lessons on the phases of the Moon.
Work through three separate animations which visually and linguistically explain the Moon
phases. When done, work through six problems which test you on your knowledge about
Moon phases.
To access this website, go to
http://www.bigkidscience.com/MoonPhases/GoMoonPhases.html