Outer Cosmos

The Big Bang

Hubble's Law

Galaxies

Big Bang Theory

• A Scientific Theory - with a capitol “T”

• At one time, the entire universe was confined to a dense, Hot, Super massive ball of hydrogen.

• Then a violent exposition triggered the rapid expansion of that Massive ball of Hydrogen

Universal Timeline

• 13.7 billion years ago (bya) The Big Bang – a violent explosion occurred spewing Hydrogen

in all directions.

• 13.5 bya first Stars formed– Over time Stars form the elements on the

Periodic Table

• 4.6 bya Solar System formed– Universe has enough elements to create the

conditions for complex life in 2-3 – billion years

Evidence

• Theory is designed to explain and connect observations – Hubble’s Law – Background Radation

Redshift & Blueshift

When a star’s spectrum is compressed from the Doppler Effect the spectrum will either shift to the red or blue end of the spectrum

• Blueshift– Moving towards you

• Redshift– Moving away from you

• The amount of compression can also tell us speed

• Galaxies are in Red shift: – deep space objects are moving away from us, the

degree of shift tells us speed

• Galaxies are retreating from us at a speed that is proportional to their distance – AKA: the further away they are the faster they are

moving

• Indicates that the universe is expanding

Hubble’s Law:

Cosmic Background Radiation

• Faint Radio Waves coming from every direction in space, though to be remnants of the Big Bang.

Galaxies

• Groups of stars, dust, and gas held together by gravity

• The universe contained hundreds of billions of galaxies

• Each containing hundreds of billions of stars

Galaxy Classification• Spiral

– Disk shaped with arms circling the center

• Barred spiral – Disk shaped with a bar through the center

and arms coming off the bar

• Elliptical– Mass of stars ranging from circular to oval

with no arms (oldest stars)

• Irregular – No discernible shape (youngest stars)

M81NGC 1300M87NGC 4449

The Milky Way• Our Galaxy, a Barred Spiral

• 100,000 light-years wide

• 1,000 - 10,000 light-years thick