The Milky Way

• What type of galaxy is our Milky Way??

• A. Spiral• B. elliptical• C. irregular

A

Ok, so how did our Universe begin??

• There are plenty of theories…– Big Bang…– Religious views…

– Everyone is entitled to what they believe. Since no one was alive when it all “happened”, everything is based on theories. Lets see what the big bang theory is all about.

BANG!

Mr. Hubble• Edwin Hubble went to Oxford University to study law.

• He wasn’t happy as a lawyer and decided to return to his passion of studying space.

• Hubble had also devised a classification system for the various galaxies he observed, sorting them by content, distance, shape, and brightness.

• Hubble found that the spectra of galaxies, except for the few closest to Earth, were shifted toward the red end of the spectrum.– If they were shifted toward the red end of the

spectrum, are they moving toward or away from the Earth??

» AWAY!

The Expanding Universe

• Using Hubble’s observations, astronomers have been able to determine that the universe is expanding.

• Similarly, galaxies in the universe are moving farther away from each other due to the expansion

of the universe.

12. Hubble’s Constant:

• This is the value given to the rate the universe is expanding.

• Rate means “something per time”• 160 km per million light years

13. Light Year:

• This is the amount of time it takes light to travel in one year.

• 9.46 trillion kilometers is the distance light travels in one year

• In miles: 5.9 trillion miles

14. Big Bang Theory

• Big Bang Theory - the theory that all matter and energy in the universe was compressed into an extremely small volume that 14 to 15 billion years ago exploded and began expanding in all directions

15. Cosmic Background Radiation

• cosmic background radiation - radiation uniformly detected from every direction in space; considered a remnant of the big bang.

• Astronomers believe that cosmic background radiation formed shortly after the big bang.

• The background radiation has cooled after the big bang, and is now about 270°C below zero.

• Absolute Zero: -273⁰C