Hubble and the Big Bang Theory By Dr. Sheldon Cooper

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

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 billion light years away We have telescopes that can see farther, but there isn’t anything viewable