Transcript synchronous rotation.

Many people have serious misconceptions about the causes of
phenomena such as seasons, lunar phases, tides, eclipses ,not to
mention the processes that formed our Earth all those billions of years
ago.
In this unit, we will attempt to
alleviate these misconceptions.
Scientists estimate the age of
the Earth to be approximately
4.6 billion years. The Earth is not
static, but still evolving…
changing. The processes that
shape the Earth still confusing
to many people.
This is a solar nebula…a nursery in space. Our solar system formed
much like this one. A collapsing interstellar cloud caused by a nearby
supernova provided the space “debris” needed for the construction of
our solar system.
The hottest densest materials clumped together in the center.
This hot dense area formed our Sun, and the inner planets, which in the
beginning were so hot they were molten.
As time passed (billions of years), these inner planets hardened into the
“terrestrial” planets they now are. These terrestrial planets are:
Mercury
Venus
Earth
Mars
In this, the Orion Nebula,
you can see evidence of
the protoplanets called
“Planetesimals” forming
through “accretion”.
Accretion is a “clumping
together” of solid objects.
The outer planets are frozen gases, and are able to exist because of their
great distance from the sun. They are sometimes called the Jovian
planets. They include:
Jupiter
Saturn
Uranus
Neptune
The rings, and large number of natural satellites
(moons) on these outer planets, are similar to miniature
solar systems themselves. As the sun formed, a huge
stellar wind blew a band of meteorites between Mars
and Jupiter, which is thought to be left over from this
early stage of development.
By studying the band of meteorites between the planets Mars, and
Jupiter, scientists have found that the solar system is about 4.6 billion
years old! They are materials from the beginnings of our solar system
that have changed relatively little since their original formation as
rocks.
Geologists use radiometric dating methods to determine the ages of
these “rocks”, many of which have bombarded the Earth through the
eons.
We are lucky that we formed
where we formed, because
Earth is the only planet in the
solar system that can sustain
liquid water, and temperate
climates, two necessities for
life, as we know it.
The moon is immensely important to the
Earth, and the life on it. It is the
second brightest object in our sky after
the sun, being only 238,850 miles from
the Earth. This brightness, of course,
comes from the reflection of sunlight,
as the moon produces no light of its
own.
The moon completes its orbit of the
Earth in one month, and interestingly
enough, rotates on its axis at the same
rate. This is a phenomena known as
Were it not for the first lunar synchronous rotation.
As our day lengthens due to rotation
probes which mapped and
slowing, (which is actually
photographed the dark side, we
happening), the lunar cycle will
would still be unaware of what it
change.
looks like.
Go to this website, and play for awhile.
Check out how the image of the Earth
changes from perspective.
http://www.fourmilab.ch/cgi-bin/Earth
It has been calculated that in one
billion years, the length of an Earth
day will be about 1080 hours. That is
45 days now!
Why would a knowledge
of Earth-Sun-Moon cycles
be important for you to
know about?
How do these cycles
affect ecosystem?
For homework tonight,
determine what stage the
moon is in now, and be
ready to reflect on it on
Wednesday!
Life is a result of the tidal forces of the Moon.
Isaac Asimov wrote in his "Tragedy of the Moon" 1972, that life evolved
in the sea did not want to move to land. There was no reason to, no
movements to force the life forms to the surface.
One look at tide pools and one can understand the purpose of this
statement - that we do life in a unique environment:
Earth would spin much faster
without its orbiting moon. That's
because the moon's gravity pulls on
Earth's oceans. The moon is largely
responsible for the tides. The pull
of the moon, and ebb and flow of
the tides, puts the brakes on Earth's
daily rotation.
The Moon has been a stabilizing
factor for the axis of rotation of
the Earth. For this reason, we had
much less climatic change than if
the Earth had been alone.
The diagram below should help you visualize the seasons.
The seasons of which hemisphere are being documented?
How do you know? What would happen if there were no tilt
to the axis? Visualize it!
1. The northern
hemisphere is being
documented, because
on Summer Solstice,
the NH is tilted
towards the sun, and
the SH is pointed
away. It would be
Winter Solstice in the
SH.
2. No tilt, means no
seasons. Eternal
Spring/Autumn!
As you can see, at summer solstice in the NH (June 21), the most direct
rays of the sun are striking the Earth at the Tropic of Cancer. This is
the farthest north the direct rays of the sun are going to ever reach,
and that is because of the tilt of the Earth’s axis.
On June 22,
the direct rays
of the sun
begin migrating
south, where
they will be
directly over
the equator
on what day?
ANS:
Autumnal
Equinox
The determination of whether it is winter, or summer
solstice is defined by the hemisphere you are describing.
The Summer Solstice in the SH (Dec 21) means the most direct rays of
the sun are reaching the Tropic of Capricorn, 23.5° S latitude. They will
never go farther south than that, because of the angle of the Earth’s
tilt.
On December 22, the
sun’s rays will begin
again moving
northward toward the
equator, where they
will be most direct on
what day?
ANS: Vernal Equinox
As you can see, this is summer solstice for the SH. It is winter solstice
for the NH.
As you can see, on the
equinoxes, the direct rays
of the Sun are striking the
equator, and every location
on Earth is receiving equal
day, and equal night.
How many daylight hours
will Vostok Antarctica be
receiving on the Equinox?
ANS: 12
How many nighttime hours
will the North Pole be
receiving on the Equinox?
ANS: 12
Without meaning to, this diagram may seem confusing, because it
appears that the Earth is not tilted 23.5°. It most certainly is tilted,
however the tilt is not a factor during the equinoxes, as this diagram
shows.
http://esminfo.prenhall.com/science/geoani
mations/animations/01_EarthSun_E2.html
When determining
proximity to the
sun, the Earth is
closest at or around
Jan 3, and this is
known as Perihelion.
(91,402,505 miles)
We are farthest
from the sun at or
around July 4, and
this is known as
Aphelion.
(94,509,130 miles)
Does aphelion, or perihelion impact our seasons at all on Earth?
No, not in the slightest!
A solar eclipse occurs when the occasional path of the moon
obliterates the path of the sun in our daytime sky. A total solar eclipse
is a relatively rare event, while a partial solar eclipse is relatively
common. Since the angle at which the moon moves above the horizon is
different, depending upon your vantage point on Earth, total and
partial solar eclipses are not visible everywhere on Earth at the same
time.
You may have been
taught as a child that
the only safe way to
view a solar eclipse
(except when the
solar corona is
apparent), is with a
pinhole camera. We
have the fortune of
having many websites
and NASA to help us
with photographs as
well.
Unlike the solar eclipse, the lunar eclipse occurs when the Earth casts
its shadow on the moon (instead of the other way around).
The night of a lunar
eclipse, there is
always a full moon.
As you can see,
during a lunar
eclipse, the moon
takes on a shadowy
appearance as the
Earth passes between
it, and the sun. It is
not totally hidden in
Earth’s shadow, but
has an eerie orange
hazy color.
Lunar eclipses can be viewed to some extent everywhere from the dark
side of the Earth. Some are partial, some are total (as seen above)
The Earth’s climate has changed much
over the course of history. Climate
change can occur from natural causes,
such as from the sun’s intensity, changes
in Earth’s orbital pattern around the sun
and natural processes within the climate
system. (like what?)
More recent impacts on climate
change have been human induced.
Humans are influencing climate through
deforestation, reforestation,
desertification and urbanization.
Manmade changes in the atmosphere’s composition
by the burning of fossil fuels like coal and oil have
trapped greenhouse gases, causing temperatures to
increase recently.
Ultraviolet
in
Infrared out
Earth’s average surface temperature has increased
from 1.2 to 1.4 degrees Fahrenheit since 1900. This may
not sound like much, but it’s enough to create changes
in rainfall patterns, snow, ice covers, and sea levels.
These humaninduced
greenhouse
gases are
detrimental
to our
environment
as they
prevent heat
from
escaping into
space. As the
concentratio
ns of these
gases
accumulate
in the
atmosphere,
the Earth’s
temperature
rises.