Hubble and the Big Bang TheoryBy Dr. Sheldon Cooperhttps://www.youtube.com/watch?v=yaX4iGw-b_Y

Review/Warm-Up

• A fire engine drives by with its sirens blaring. Explain, in terms of wavelength and frequency, why the siren sounds louder as the truck approaches and softer right after it passes by.• What is spectroscopy? Name two ways scientists use

spectroscopy.• Which color of light is associated with the least amount

of energy? • Which color has the shortest wavelength?

Edwin Hubble, Astronomer• 1920s study of “fuzzy

spots” in nighttime sky• Working with the new

100-inch-wide telescope California, discovered that the “fuzzy spots” were huge collections of far-away stars called galaxies

Hubble’s Redshift• Light from the

galaxies match the spectral lines for Hydrogen• The lines are shifted toward the red (lower

frequencies)• Hubble realized this was the Doppler Effect:

lower frequencies = objects moving away• ALL galaxies did this!

Expanding Universe

• Hubble’s Law:• Galaxies are moving away from us.• The farther away the faster they go.• If galaxies are all moving away, then at

some point they were all much closer.• Hubble’s Law implies the Universe is

expanding.

Hubble Video• http://www.youtube.com/watch?v=hVApTLE7Csc• https://www.youtube.com/watch?v=1eePtgqReD4

The “Big Bang” Theory • The universe begins

~13.7 Billion years ago• The universe begins as

the size of a single atom• The universe began as a

violent expansion• All matter and space

were created from a single point of pure energy in an instant

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.

~ Several hundred thousand years after Big Bang• ATOMS form

(specifically Hydrogen with a small amount of Helium.)• The early Universe

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

WMAP telescope image of first atoms after Big Bang

~200 to 400 million years after Big Bang

• Hydrogen clumps into huge collections• Galaxies form• Stars born within

galaxies

Fusion in Stars• HUGE amount of heat and

pressure in center of a star• Heat causes H atoms to

stick together, creating Helium• This releases

LOTS of energy• This called fusion• As a star ages, it also

creates lithium, carbon, oxygen

~ 4.6 billion years ago• Our Solar system forms• Supernova• Heat causes atoms to

fuse together to create all other elements• Materials blown out of

a supernova become a star and planets for a new solar system!

Speed of light and stellar distances• The speed of light is a universal constant of

300,000 km/sec• We observe stars millions/billions of light-years

away• A light-year is the distance that light travels in 1

year – the light we see today from a star 500 light years away is 500 years old• The farthest stars away are 10-14 billion light

years away• We have telescopes that can see farther, but

there isn’t anything viewable