Earth/Moon/Sun System
How the Earth, Moon and Sun interact to create fascinating phenomena
Electromagnetic spectrum

Review the spectrum

From longest wavelength to shortest:

Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays

Short wave length means higher frequency

Long Wave length means lower frequency
How scientists “view” the universe

Telescopes

Telescopes gather electromagnetic radiation and focus it into a single image

The Larger the opening of a telescope (aperture), the more light (EM
radiation) it can collect

Amateur telescopes can range up to half a meter (16-18 inches) in aperture

Where as currently the largest telescopes on Earth have apertures of up to 10
meters (approx. 33 ft – about the length of the portable)

Earth-based telescopes that are under construction will go as high as 38
meters in aperture (approx. 127 ft)
Visible light telescopes

Two types of visible light telescopes:

Refracting and Reflecting

Refracting telescopes use lenses to bend light into a single image

Reflecting telescopes use mirrors to focus light into a single image
Astronomyspot.com
Refracting vs. Reflecting

The largest refracting telescopes have apertures only a few inches in
diameter, this is because manufacturing larger lenses that are quality is very
difficult and costly


The larger the lens, the longer the telescope needs to be to focus the image
To have larger apertures, scientists use reflecting telescopes because mirrors
are much easier to make and maintain.

Many mirrors can also be combined to create extremely large apertures.

Reflecting telescopes can be relatively compact
http://www.astro.ufl.edu/~guzman/ast1002/class_notes/Ch3/telescopes.html
Non-visible wavelength telescopes

Infrared and UV rays can be
focused using regular mirrors

X-rays need a special design to
focus

Gamma rays, at this time can not
be focused so only the direction
can be determined


Radio waves need large dishes,
like satellite dishes to collect,
and a computer to convert to
electric signals to be analyzed
later
Resolution of radio and visual
telescopes can be made better
by interferometry (technological
process that combines several
sources into one)
Arecibo Observatory – Puerto Rico
(https://en.wikipedia.org/wiki/Arecibo_Observatory)
VLA (Very Large Array) – in
New Mexico
http://www2.astro.psu.edu/users/niel/astro1/slid
eshows/class29/008Very_20Large_20Array_20Radio_20Telescope_20NM
_20e.jpg
The Moon

First space probes on the moon, 1957, with launch of Sputnik I

First satellite around the moon, 1959, Soviet: Luna 2

First Human in space, 1961, Soviet cosmonaut, Yuri A. Gagarin

Same year, First American in space, Alan B. Shepard Jr. in Project Mercury

First American to orbit the Earth, 1962, John Glenn

Americans then on to two man teams: Project Gemini

First humans on the Moon, Apollo 11, July 20th, 1969, Americans Neil
Armstrong and Edwin “Buzz” Aldrin, (Michael Collins was in command module)
Landed in: Mare Tranquillitatis (Sea of Tranquility)

Continued to Apollo 12,13,14,15,16,17

Program discontinued after Apollo 17 (launched 1972)
Moon
Moon landing spots
Near and far side of moon
http://voices.nationalgeographic.com/files
/2014/07/Apollo-landingspots.jpg
http://www.slate.com/content/dam/slate/blogs/bad_astron
omy/2014/06/16/lro_nearside_farside_590.jpg.CROP.original
-original.jpg
Moon Facts

Formed 3.8 to 4.6 billion years ago, current scientific theory is an impact of Earth from a
Mars sized object threw out the material that coalesced into the moon.

Lunar rotation (spin) is 27.3 days

Lunar revolution of Earth (going around Earth) is 27.3 days

Lunar surface is actually fairly dark, the Albedo (percentage of sunlight reflected) is
about 7%

Earth has an albedo of about 31%

In direct sun, surface temperature is 400 K (127 Celsius) (261 Fahrenheit)

Unlit side, surface temperature can be 100 K (-173 Celsius) (-279 Fahrenheit)

Average distance to moon: 238,855 miles (384,400 km) (30 Earths) (1.3 Light seconds)

Moon is moving away from Earth at 3.8 cm per year

Earth rotation is slowing, in 100 years, a day will be 2 milliseconds longer (1/500 second)

http://curious.astro.cornell.edu/about-us/37-our-solar-system/the-moon/the-moon-and-the-earth/111-is-the-moon-moving-away-from-theearth-when-was-this-discovered-intermediate
Moon Features

Highlands – heavily cratered areas that are
mountainous

Mare – plural Maria, smooth plains which average 3
km less in elevation than highlands – formed from
lava flows – only a few craters

Craters have Ejecta and Rays

Ejecta are blankets of debris that fell down after
impact

Rays are streaks that spread out from craters

Riles are valleys that may have been lava tubes

Regolith is ground up rock that covers the moon
surface, thickness varies from several meters to a
few centimeters depending on location
Moon Interior

The lunar crust is thinner on the near side that
faces the Earth, and thicker on the far side.

Fractures in the thin crust have allowed magma
to reach the surface on the near side, where the
lava-filled Maria are concentrated.

The Moon has an iron-rich core with a radius of
about 20 percent of the Moon's average radius.

The Moon's center of mass (CM) is offset by 2000
meters from its center of figure, CF

Therefore magmas originating at equipotential
depths will have greater difficulty reaching the
surface on the far side.
https://ase.tufts.edu/cosmos/print_images.asp?id=5
Earth Daily Motions

Solar Day: from one noon to the next
on Earth (24 hours)

Which is actually 4 mins longer than
the time Earth takes to rotate 360
degrees? Why?

As the Earth is rotating, it is also
revolving, so it has moved around the
sun a bit, so to rotate back to where
the sun is in the same spot as the day
before, it takes 4 more minutes

The rate it takes the Earth to rotate
360 degrees is called a Sidereal day
(23 hours 56 minutes)
https://sureshemre.files.wordpress.com/2014/04/sidereal_solar_explanation.jpg
Earth Annual Motions

The Earth revolves around the Sun in the Ecliptic
Plane, the path the sun looks to make in the sky is
the ecliptic

The Earth is tilted relative to the Ecliptic plane by
23.5 degrees

This tilt is what causes the seasons

The time of the year when the sun is directly
overhead on the farthest northern or southern
latitude is called the solstices

When the Sun is directly overhead of the equator it
is called an equinox

The Autumnal and Vernal equinoxes are opposite in
the southern hemisphere
http://www.physlink.com/education/askexperts/Images/ae495a.gif
http://spaces.imperial.edu/russell.lavery/ASTR100/Lectures/Topic02/topic02-sunalt.gif
Sun Changes in altitude

Altitude is the angular elevation above the horizon
http://spaces.imperial.edu/russell.lavery/ASTR100/Lectures/Topic02/topic02-sunpath.gif
Moon Phenomena

Huge Moon

“How we perceive the Moon's size has to do
with how far away we think it is based on
what's around it.”

“Most of us see the top Moon, seemingly
located in the distance based upon the
convergence of the railroad tracks, as larger
than the bottom Moon. Yet they're
identical.” (Ponzo illusion)
(Picture and text) http://www.skyandtelescope.com/observing/moon-illusion-confusion11252015/
https://ase.tufts.edu/cosmos/print_images.asp?id=5
Lunar Motions

The time it takes the Moon to
go through a cycle of phases
(from one new moon to the
next) is 29.5 days: this is a
Lunar Month

The time it takes the moon to
go 360 degrees around the
Earth (Lunar Revolution) is 27.3
days

The moon rises and sets 50
minutes later each day because
the moon moves 13 degrees in a
24 hour period
Moon Phases
• The phases go from
right to left, like a
book
• The horizon is a
tangent on the Earth
• Know the Moon
phases from New
Moon to New Moon
Moon rise and set times
http://www.physast.uga.edu/~jss/1010/ch2/02-21.JPG
Moon Phenomena

Tides

The Sun and Moon create a tidal bulge

The affect from the Moon is more significant than the effect of the sun

As the Earth rotates, it moves through the bulges. How high and low and how
many tides and at what time they occur is a very complex process.

“The Earth's rotation twists the closest bulge ahead of the Earth-Moon line
(dashed line), and this produces a lag in time between the time the Moon is”
directly overhead and the highest tide.
https://ase.tufts.edu/cosmos/print_images.asp?id=5
http://earthsky.org/earth/tides-and-the-pull-of-the-moon-and-sun
Spring and Neap Tides
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“The height of the tides and the phase of
the Moon depend on the relative
positions of the Earth, Moon and Sun.”

“When the tide-raising forces of the Sun
and Moon are in the same direction, they
reinforce each other, making the highest
high tides and the lowest low tides.”

“These spring tides occur at new or full
Moon.”

“The range of tides is least when the
Moon is at first or third quarter”

https://ase.tufts.edu/cosmos/print_imag
es.asp?id=5
Tides May 2017 –
Pensacola Beach
http://www.tides4fishing.com/us/floridawest-coast/pensacola#_tides
Moon Phenomena

Lunar and Solar Eclipses

“The Moon's orbit is titled 5 degrees to the
Sun's route across the sky, the ecliptic,
allowing these paths to cross at two nodes.”

“These are the only points at which eclipses
can occur.”
https://ase.tufts.edu/cosmos/print_images.asp?id=5
Lunar Eclipse

“During a lunar eclipse the initially full Moon passes through the Earth's shadow.

A total lunar eclipse occurs when the entire Moon moves into the umbra.

Because no portion of the Sun's surface can be seen from the umbra, it is the darkest part of
the Earth's shadow.

Only part of the Sun's surface is blocked out in the larger penumbra.

A partial lunar eclipse occurs when the Moon's orbit takes it only partially through the umbra
or only through the penumbra.”

https://ase.tufts.edu/cosmos/print_images.asp?id=5
Lunar Eclipse – Red Moon

“During a lunar eclipse the Moon and
Sun are located at opposing nodes, so
that the Moon can move into the Earth's
shadow cast by the Sun.”

“If the Earth had no atmosphere, the
Moon would disappear in darkness
during a total lunar eclipse”

“As shown here, the Moon actually
becomes dark red for an hour or so.”

“This is because the Moon is illuminated
by sunlight that is bent part way around
the Earth and is reddened in passing
through the Earth's atmosphere, just as
the Sun is reddened at sunset.”

https://ase.tufts.edu/cosmos/print_im
ages.asp?id=5
Solar Eclipse

”During a solar eclipse, the Moon casts its shadow upon the Earth”
https://ase.tufts.edu/cosmos/print_images.asp?id=5

Three types of solar eclipses: Total, Annular, Partial

Total is in Umbra (about 270 km wide), Partial is in Penumbra
https://c.tadst.com/gfx/750x500/types-of-solar-eclipses.png?1
https://www.exploratorium.edu/sites/default/files/SolarEclipse.jpg
Solar eclipse – Total vs Annular
• Annular is when the moon is
either too far or too close to
completely cover the sun for
a total eclipse
http://thesuntoday.wpengine.netdna-cdn.com/wp-content/uploads/2013/11/Solar_eclipse_geometry.jpg
Solar Eclipses – 2001 to 2020
https://eclipse.gsfc.nasa.gov/SEatlas/SEatlas3/SEatlas2001.GIF
Solar Eclipse in USA – August 21, 2017
https://www.sciencenews.org/sites/default/files/2016/08/082016_Solar_eclipse_inline-NEW.png
https://eclipse.gsfc.nasa.gov/SEatlas/SEatlas3/SEatlas2041.GIF
https://eclipse.gsfc.nasa.gov/SEatlas/SEatlas3/SEatlas2021.GIF