THE BIG BANG THEORYThe most commonly accepted theory

today of the formation of the universe is the Big Bang Theory.

The theory states that the universe originated sometime between 10 billion

and 20 billion years ago from an enormous explosion of a small volume of

matter at extremely high density and temperature. (Scientists believe our universe comes from a singularity.

Scientists don't actually know where this singularity came from or exactly what it is, but they do know that a singularity is an infinitely small, hot area of infinite pressure and

density.)

Astronomers use the analogy of cooking

raisin bread to demonstrate the expanding

universe

Expanding the Universe on a Balloon Demo

Evidence: Copy in the

three columns

1.→ Cosmic Microwave Background

- faint radiation left over from the

expantion itself

2.→ Red shift: Wavelengths of light

from distant galaxies

3.→ Mixture of Elements: The matter in

the universe is about 75% hydrogen &

25% helium atomic creation.

Cosmic Microwave

Background Radiation (CMB)

• CMB is the “after glow” or “leftovers” from the big bang that

permeates (spreads) in all directions of the universe.

• Physicists agreed that CMB was leftover ‘heat’ in the form of

microwave radiation, which was still cooling from the Big Bang.

• Original temperature of the universe: 3000 Kelvin

• Today, universe is approximately 3 Kelvin

• The amount of cooling says how far the light has travelled, which determined the age of the universe: 13.82 billion years.

Redshift of Galaxies

• The apparent wavelength lengthens as the galaxy moves away from the observer. The Velocity of galaxies can be calculated: v = H x d

• The exact value of the Hubble constant is still somewhat uncertain, but is generally believed to be around 65 kilometers per second for every megaparsec in distance.

• If most galaxies are moving away from each other, then the universe is expanding outwards from a central point.

• Hubble’s Space Telescope (named after Edwin Hubble) was important in determining recessional velocity of galaxies.

*Remember, red color has a longer wavelength than blue – therefore, it is moving away!

1. Universal expansion and Hubble’s

Lawa) Hubble observed the majority of

galaxies are moving away from us

and each other

b) The farther, the faster they move

c) Red Shift

Mixture of Elements• The matter in the universe is about 75% hydrogen & 25%

helium.

• •The abundance of H & He supports a particular process of past atomic creation, where the larger elements formed from the smaller elements. Predicts how much of each element should have been made in the early universe, and what we see in very distant galaxies and old stars is just right. You cannot look in new stars, like the Sun, for this evidence, because they contain elements that were created in previous generations of stars. As such, the composition of new stars will be very different from the composition of star.

~ Several hundred

thousand years after Big Bang

• ATOMS form (specifically Hydrogen and its isotopes with a small amount of Helium.)

• The early Universe was about 75% Hydrogen and 25% Helium. It is still almost the same today.

Misconceptions about

the Big Bang

• there was no explosion; there was (and continues to be) an expansion• Rather than imagining a balloon popping and

releasing its contents, imagine a balloon expanding: an infinitesimally small balloon expanding to the size of our current universe

• we tend to image the singularity as a little fireball appearing somewhere in space• space began inside of the singularity. Prior

to the singularity, nothing existed, not space, time, matter, or energy - nothing.

WHY DO THEORIES CHANGE?

▪ Scientific theories change when scientists

discover new information

▪ New technology, new tools, and/or new

observations can provide new information.

▪ Think back to the Theory Challenge

Activity. What new technology and/or tool

was mentioned?

Greater telescopes and imaging technology

AN INSTRUMENT USED TO DETECT RADIO

EMISSIONS FROM THE SKY, WHETHER FROM

NATURAL CELESTIAL OBJECTS OR FROM

ARTIFICIAL SATELLITES.

THE GREAT DEBATE! MODELS OF

THE SOLAR SYSTEM ACTIVITY

SCENE: COURTROOM YEAR 1610

GEOCENTRIC

PTOLEMY’S MODEL OF THE SOLAR SYSTEM

▪ Ptolemy’s theory is known asthe Geocentric Model because he thought the Earth was the center of the universe

▪ In Greek, “Geo” means earth▪ He believed his theory for

several reasons▪ Gravity of all objects were

attracted to the earth, which suggested to him that the earth must be the center.

▪ He thought the Earth did not move because objects fell in the same place if thrown up in the air. He thought if the earth moved, objects would

COPERNICUS’ MODEL OF THE SOLAR SYSTEM

▪ Copernicus’ theory is called the Heliocentric Theory because he thought the sun was the center of the universe.

▪ In Greek, “helios” means sun

▪ Galileo made additional observations using a telescope which supported the heliocentric theory.▪ Galileo observed that

Venus went through a full cycle of phase’s like the Moon. This could only be explained if