Transcript The Earth in Space - Buncombe County Schools System

Earth’s Movements
in Space
• OK, we already know that at the very
beginning there was a huge explosion
called the Big Bang.
• It created everything there ever was
and all there is now, which is the
whole universe (all of space).
• It was extra-super-incredibly hot, and
it had to cool down a lot for galaxies
to form.
• The universe is everything there is, all
that exists. It is made of galaxies…
maybe about 200 billion
• A galaxy is made of stars… maybe about
200 billion for each galaxy
• Our galaxy is called the Milky Way
• Scientists were unsure about how many
galaxies the universe contained until they
took the following pic in 1975 called the
Hubble Deep Field View…
• This aint it...
• This is a galaxy. Before we see the Hubble
Deep Field View, remember…
the pic shows a region of the sky smaller than a
sand grain held at arms length and each point of
light is a galaxy!
• The Hubble Deep Field View showing over
3000 galaxies!.
• OK…back to the order of the
universe. After galaxies comes stars.
• After stars comes planets.
• Maybe a third of all stars have 1 or
more planets – wow
• Earth is a planet going around a star
(the sun)
• We are the only planet of zillions that
has life on it that we know of
• OK, so here’s the order again: Universe…
…Galaxies (Andromeda), our nearest
neighbor
…Inside galaxies and smaller than
whole galaxies are planetary systems
like our solar system! Stars with
planets and possibly moons orbiting
them
…and stars (Sun)
• With Earth - moving around the sun
• But that’s not our only motion…
• PS – this is a real photo of Earth taken
while orbiting the moon.
Earth’s Many Motions
1.
2.
3.
4.
Rotation
Revolution
Precession
Nutation
1. Rotation = the spinning on our axis.
- takes about 24 hours (actually 23 hours
& about 56 minutes).
- our axis is tilted 23 ½ degrees.
- the range is 22 - 24 degrees and
cycles about every 41,000 years.
- that tilt gives us seasons…more
later
- Currently we are pointed at the
North Stars as we orbit the sun.
2. Revolution = going around the sun.
- Also called our orbit
- Takes about 365 ¼ days.
- That extra ¼ day is the reason for
a leap year.
- Our orbit goes from more oval to
more round every 100,000 years
3. Precession = the wobbling of Earth like
a top as it spins (on its axis)
- cycles every 26,000 years
- caused by the sun and moon pulling
on Earth’s bulges…yes, bulges.
- Earth bulges at the equator as it
spins, like a water balloon would
bulge if you tossed it into the air.
4. Nutation = the wobbling of Earth’s
precession (its wobble) as it
wobbles!
- This has an 18.6 year cycle.
- It is caused by the moon orbiting
the Earth at a slightly tipped angle,
say 5° from being flat.
How Else Does Earth Move?
• Besides just going around the sun…
the galaxy spins around its center
taking our solar system with it.
• And the galaxy moves through the
universe as the universe expands.
• Yes, our universe is getting bigger.
• WOW…and that’s not even all of it
A Bit More Movement
Gravity is why the planets orbit the sun.
The sun pulls on them all and they all
pull back. (Mass & Distance)
The pulls of gravity equal each other.
It’s like a see-saw or teeter-totter with a
big kid on one side and a small kid on
the other side. The big kid has to sit
closer in to “balance” the teeter-totter.
Gravity must balance out with the sun
and all the planets pulling on each
other.
This “balance point” is called the
barycenter.
Think of it as the “center of gravity”
among all the planets and sun.
They all orbit around this barycenter or
center of gravity
So the sun actually “rocks” back and
forth from orbiting the barycenter.
The planets do the same except you
can’t really tell ’cuz they have big
orbits.
• The same thing occurs with the sun and
the planets, but the barycenter is inside
the surface of the sun ’cuz it’s so massive.
http://en.wikipedia.org/wiki/File:Orbit3.gif
• The same thing happens with the
Earth-moon system.
• They both orbit their common center of
mass called the barycenter.
• And again, that location is just inside the
surface of Earth.