IX. Earth’s Place in the Universe

A. Light Year

1. The DISTANCE light travels in one year

2. 6,000,000,000,000 miles

3. The speed of light is 186,000 miles per second

Mercury- 3.2 minutes Venus- 6 minutes Earth- 8.3 minutes

Mars – 12.7 minutes

B. The time it takes sunlight to reach:

1) The nearest star Alpha Centauri =

2) the brightest star Sirius=

3) The nearby Andromeda Galaxy =

Jupiter- 43.3 min Saturn- 1hr 20 min

Uranus- 2hrs 40min Neptune- 4hrs 10min Pluto- 5hrs 30min

4.3 years8.6 years

2,000,000 years

4. a. We see all night stars as they WERE when the light

b. When we look at distant stars and galaxies, we look back in

B. Galaxies

1. Billions of stars held together by gravity

2. Shape of Galaxies:

b. elliptical

c. irregular

Left that star

TIME

a. spiral

C. The Milky Way Galaxy

1. Our sun is only one of the estimated 180 billion.

2. The milky way is a spiral galaxy.

a. Top View

b. Side View

D. Levels of Structure of the Universe

1. Planet Earth- a small dense rocky planet

2. Our Solar System- Earth is one of eight planets that orbit the sun- an average yellow star.

3. Milky Way Galaxy- Our sun/solar system is on of an estimated 180 billion stars making up one spiral galaxy.

4. Universe- Our Milky Way Galaxy is one of billions of galaxies in an expanding universe.

X. Evolution of the Universe

A. Electromagnetic Energy

1. The is the major energy source for weather changes in the atmosphere and many of the changes occurring at Earth’s surface.

2. Energy from the Sun comes in

sun

many different wavelengths.

3. The Big Bang Theory (Yes, it is more than just an awesome T.V. show!)

a. In the late 1920’s, Edwin Hubble discovered that ALL the galaxies were “red-shifted” when viewed from Earth. This meant that all galaxies were moving away from Earth and each other, and thus, the universe must be expanding!

b. This led to the theory that the universe began a cosmic explosion that occurred 15 to 20 billion years ago. The universe we live in today has evolved from this explosion of matter and energy.

c. An echo of background radiation can still be detected by radio telescopes.

d. The data table below shows the distances of some galaxies from Earth. It also shows the “red-shift” of each galaxy and how many units of red shift are exhibited by each galaxy.

1. The amount of “red shift” is a result of the speed at which the galaxy is moving.

2. CONCLUSION: As the distance from Earth increases, the amount (degree) of red shift of a galaxy increases; this indicates that the farther a galaxy, the faster it is moving.

4. Evolution of the Universe

5. Future of the Universe

a. Determining factors:

1. mass

2. gravity

b. Open Universe- NOT enough mass

Therefore: not enough gravity, universe continues to expand.

c. Closed Universe- enough mass

Therefore: enough gravity to stop expansion- result BIG CRUNCH

IV. The Solar System- The sun and all celestial bodies held by the sun’s gravity and orbit the sun

Planetary Symbols

B. The Planets

1. Relative size of the Sun and the

planets

2. Orbit of the planets and their relative distance

V. Kepler’s laws of planetary motion

A. Law 1- The orbit of each planet is an ellipse, and the sun is at one foci

1. An ellipse

2. Eccentricity- a measurement of the “shape” of an ellipse.

A. Formula: eccentricity= distance between foci length of major axis

B. Eccentricity Problems – use your ESRT to measure distance between the foci and the length of the major axis for each of the 3 ellipses

C. Relationship: As the distance between foci increases, the shape of the ellipse

becomes more elliptical/oval.

B. Law 2- As a planet orbits the sun, its orbital speed changes and is fastest when closest to the sun

1. perihelion- point in orbit nearest to sun

2. Aphelion- point in orbit farthest from sun

C. Law 3- The farther a particular planet is from the sun, the longer its period (time) of revolution.

1. Farther planets have longer, orbital paths

2. Farther planets have slower orbital speeds

II. Gravity

A. Newton’s Law of Gravity

1. All objects possess gravity and will pull all other objects with

a certain gravitational force.

2. The mass of an object determines the amount of gravitational force that object possesses. The

greater the mass, the greater the gravitational force.

3. The gravitational force between two objects changes as the distance between them change. As

distance increases, gravity decreases.

B. Gravity and Inertia

1. Newton’s Law of Inertia states that… An object’s motion will not change unless that object is acted on by an outside force.

2. Inertia + Gravity= Stable Orbit

b. Gravity- pulls a planet towards the sun

a. Inertia- causes a planet to move in a straight line