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 Motions1. Rotation

2. Revolution

3. Precession

4. 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.

• 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

How Else Does Earth Move?

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.

A Bit More Movement

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.