1. How the Universe got its Spots
The Big Bang

2. Goals Where did the Universe come from? Where is it going?
How can we see the past?
How can we learn about the future from seeing the past?

3. Time line: Cosmic Soup, Radiation Era, Matter Dominated Era

4. The Big Bang
Big Bang: the event from which the Universe began expanding.
Into what did the Universe expand?
Where was the Big Bang?
Where is the center of the Universe?

5. The Big Bang theory states that approximately 14 billion years ago the universe burst into being from an unknown cosmic trigger. The early universe, contained within just a few millimeters, was very hot and densely packed with matter called a SINGULARITY. Ever since that initial explosion, the universe has continued to expand and cool.

6. Consequences
If everything is moving away from us and things farther are moving faster
Then the Universe is expanding!
This doesn’t mean what you are probably thinking

7. Expanding Universe
Space itself is expanding, not matter flying apart within space.
Examples:
dots
rubber band
raisin bread
ants on a balloon
It does not mean we are at the center of the Universe
every part of the Universe sees everything moving away from it

8. Looking Back in Time Remember it takes time for light to reach us
travels at 300,000 km/s
So we see things “as they were” some time ago
The farther away, the further back in time we are looking
1 billion LY means looking 1 billion years back in time
So the greater the redshift, the further back in time
redshift of 0.1 is 1.4 billion lightyears which means we are looking 1.4 billion years into the past

9. Big evidence for Big Bang
George Lemaitre proposed the idea that the universe was expanding in 1927
He named it the “Hypothesis of the primeval atom”  there was a definite beginning to the universe universe

10. 1. Galactic Redshifts l Z = [(1+ v/c)/(1+ v/c)]1/2 - 1
Edwin Hubble ( ) and colleagues
measured the spectra (light) of many galaxies
found nearly all galaxies are red-shifted
Redshift (Z)
rest l - =
observed
Andromeda galaxy
Z = [(1+ v/c)/(1+ v/c)]1/2 - 1

11. Redshift happens when light seen coming from an
Quasars & Cosmology
Redshift
Redshift happens when light seen coming from an
object that is moving away has shifted (towards the red end of the spectrum)
Department of Physics, Applied Physics & Astronomy, RPI

12. Do you know what Red Shift is?
Remember: the Red is the longest wavelength while Purple is the shortest.

14. What does Redshift mean for the BIG BANG Theory?
If all of the galaxies are redshifted, then they are ALL moving apart from each other!!
(This is proof that the Universe is expanding)

15. 2. Hubble’s Law Galaxies are moving away from us.
B. The farther away the faster they go!

16. Expanding Universe
If galaxies are all moving away, then at some point they were all much closer.
Hubble’s Law implies the Universe is expanding.

17. 3. Cosmic Background Radiation
CBR is radiation left over from the explosion of the Big Bang discovered by Arno A. Penzias and Robert W. Wilson.
It is similar to the radiation leftover after a nuclear bomb.

18. Look back Time
We see everything as it once was.
Present
Young Early

19. Age of the Universe
Since all galaxies are moving away from us, how long has it been since all galaxies were together?
time = distance / velocity
velocity = Ho x distance
time = distance / (Ho x distance)
time = 1/Ho
“An expanding universe does not preclude a creator, but it does place limits on when he might have carried out his job.”
-Steven Hawking, A Brief History of Time

20. The End of the Universe Will the universe expand forever?
Depends on the density of the Universe.
Too big: Big Crunch
Closed Universe
Bound Universe
Too small: Big Freeze
Open Universe
Unbound Universe

21. Hubble Space Telescope
Use HST to find Cepheids in other galaxies.

22. Baby Boomer Universe 90s 80s 70s 60s 50s 40s
Farther away we look, further back in time we see!

23. What We See

24. Density of the Universe
Add up all the mass we see and Wo = 0.01
But we know there is some dark matter in galaxies and clusters.
How much?
Think ~10 x more dark matter than “light” matter.
Cosmologists think Wo < 0.3
Result: Open Universe  Big Freeze!

25. Are We Slowing Down? In our experience, things slow down over time.
Distance (Lookback time)
Present
Past
In our experience, things slow down over time.
Is the Universe slowing down at all?
Plot distance versus velocity.
Use supernovae as “standard candles.”
Distant supernovae (large lookback time).
V=HoD
Slowing
Accelerating

26. Are We Slowing Down? Unseen mass making stars move fast: Dark Matter
Accelerating
Unseen mass making stars move fast:
Dark Matter
Unseen energy accelerating galaxies:
Dark Energy

27. We are not made of the same type of matter as most of the Universe!

28. Concluding comments
"Astronomy leads us to an unique event, a universe which was created out of nothing and delicately balanced to provide exactly the conditions required to support life…the observations of modern science seem to suggest an underlying, one might say, supernatural plan…“ [Nobel Laureate Arno Penzias ]
“the origin of life appears to be almost a miracle, so many are the conditions which would have had to be satisfied to get it going…” [Nobel Laureate Francis Crick]

29. Some references
John D. Barrow and Frank J. Tipler, The Anthropic Cosmological Principle (New York: Oxford University Press, 1996)
J. P. Moreland (ed.), The Creation Hypothesis (Downers Grove, Illinois: InterVarsity Press, 1994)
Charles B. Thaxton, Walter L. Bradley, and Roger L. Olsen, The Mystery of Life’s Origin: Reassessing Current Theories (Dallas: Lewis and Stanley, 1992)
Robert Shapiro, Origins: A skeptic’s guide to the creation of life on earth (New York: Summit Books, 1986)