OUR UNIVERSEFarmington Jr. HighMr. Pratt

QUIZ TOMORROWHere are a few things to know

ONLINE TEXTBOOK: CHAPTERS 28-30The text goes over a number of details we will not cover, so use it as a resource to help understand the main ideas of this presentation.

TWO MAIN POINTSThe Universe

• The big bang theory explains the formation of our universe.

• Estimated to be 13.7 B years old.• Contains billions of galaxies with

billions of stars in each of them.• Evidence: redshifting, cosmic

background radiation, EM spectra.

The Solar System• The nebular theory explains the

formation of our solar system.• Estimated to be 4.6 B years old.• The Sun is the center of the solar

system with surrounding planets.• Evidence: gravity, motion,

temperature, observation of other stars.

THE KNOWN UNIVERSE• We can only study what we

are able to observe.• Our observable universe

contains everything that we can receive information from, since the beginning of time.

THE BIG BANG• Universe formed from unknown (nothing/energy) into

EVERYTHING we now have.• Began with simple sub-particles that eventually formed

hydrogen.• Gravity was the key ingredient that brought things

together as the first bits of matter began to cool.• As matter cooled, it slowed down enough to create the

first hydrogen atoms.

THE BIG BANGREDSHIFT OF GALAXIES

• Edwin Hubble discovered the universe was expanding!

• The Doppler effect explains how waves appear shorter or longer if an object is moving toward or away from you.

• The EM light spectrum show more red with longer wavelengths, and galaxies moving away from us shift toward the red side.

• Most galaxies are redshifting!

THE BIG BANGCOSMIC BACKGROUND RADIATION

• Two scientists using radio technology received “background radiation.”• They cleaned and tested the

equipment, trying to find an explanation.• Eventually they concluded it was

EM radiation constantly reaching Earth—in other words, it was the first waves ever emitted!• Cosmic Background Radiation

THE BIG BANGCOSMIC BACKGROUND RADIATION

• As the universe was cooling, the energy that was changing into matter stayed as matter, and began to emit EM waves.• These were the first EM waves

emitted and are still being emitted today… those hydrogen protons exist even now!• The radiation they gave off 13.7

Bya is reaching us as cosmic background radiation!

OUR SOLAR SYSTEM

THE NEBULAR THEORY• Our solar system was formed from

a cloud of gas and dust that was sent spinning by some force.

• The spinning caused the cloud to flatten like a disk, then eventually the “dust” collided and collapsed due to gravity.

• A central star was born.• The remaining dust eventually

formed planets, moons, and asteroids.

a) Dust & Gas

b) Flattens due to spinning

c) Gravity of Sun pulls in most matter

d) Accretion disk forms

e) Planetismals Protoplanets Planets form

THE NEBULAR THEORYPLANET FORMATION

Inner Rocky Planets• Mercury, Venus, Earth, Mars• At enough distance from the Sun

for most solid metals and rocks to form.

• Made of matter from initial dust cloud (nebula material from previous stellar supernova).

• Made spherical over time.

Outer Gas Giants• Jupiter, Saturn, Uranus, Neptune• Far enough from Sun that gases

freeze or solidify. • Less-dense gases accumulate

around protoplanet, causing the mass to increase rapidly.

• Clear out LARGE orbits because of the large mass (greater gravity).