1. The Big Bang Theory proposes that the universe began approximately 13 billion years ago with the rapid expansion of matter and energy from a hot, dense state. 2. Edwin Hubble discovered that galaxies exist outside the Milky Way and are moving away from each other, providing evidence that the universe is expanding. 3. Evidence for the Big Bang includes the cosmic microwave background radiation, which is remnants of light from the early universe, and relative abundances of light elements like hydrogen and helium.

1. Matter UnitMatter Unit
Learning Goal #1: RecognizeLearning Goal #1: Recognize
the origin and distribution ofthe origin and distribution of
elements in the universe.elements in the universe.

2. Edwin HubbleEdwin Hubble
 First to realize that galaxiesFirst to realize that galaxies
lie outside the Milky Way …lie outside the Milky Way …
 …… by measuring their distancesby measuring their distances
using Cepheid variables asusing Cepheid variables as
‘standard candles’‘standard candles’
Edwin P. Hubble (1889-1953) was
trained as a lawyer, before boredom
made him turn to astronomy instead
Cepheid variables oscillate in brightness with a regular period
that depends on their luminosity. By measuring this period,
they can be used as standard candles.

3. Cosmic SpeedometerCosmic Speedometer
 When a galaxy is receding, lightWhen a galaxy is receding, light
waves travelling to us are red-waves travelling to us are red-
shiftedshifted
 Hubble measured the spectrumHubble measured the spectrum
of these galaxies and found theof these galaxies and found the
spectral lines to be red-shiftedspectral lines to be red-shifted
o The faster the recession, the
greater the red-shift

4. Doppler EffectDoppler Effect
 Doppler EffectDoppler Effect is the shift in frequency andis the shift in frequency and
wavelength of waves which results from a sourcewavelength of waves which results from a source
moving with respect to the medium, a receivermoving with respect to the medium, a receiver
moving with respect to the medium, or even amoving with respect to the medium, or even a
moving medium.moving medium.

6. Expansion of the UniverseExpansion of the Universe
… ‘winding’ backwards, the universe must have had a beginning

8. Georges Lemaître (1894-1966) was
a Belgian Catholic priest who was
fond of saying there is no conflict
between science and religion
Georges LemaîtreGeorges Lemaître
 Proposed that the universe began with theProposed that the universe began with the
explosion of a ‘primeval atom’explosion of a ‘primeval atom’
 His model was improved by George GamowHis model was improved by George Gamow
and others, who proposed that elements wereand others, who proposed that elements were
forged during this hot and dense stageforged during this hot and dense stage
 Known as the Big Bang theory today; coinedKnown as the Big Bang theory today; coined
by Fred Hoyle who proposed a rival theory ...by Fred Hoyle who proposed a rival theory ...

9. Steady State ModelSteady State Model
 Universe is expanding, but maintainsUniverse is expanding, but maintains
a constant average densitya constant average density
 Matter is continually being created inMatter is continually being created in
the voids to form new stars, galaxiesthe voids to form new stars, galaxies
 Universe has no beginning and no endUniverse has no beginning and no end
 But disproved with the discovery of …But disproved with the discovery of …

10. Cosmic MicrowaveCosmic Microwave
Background (CMB)Background (CMB)
 Background radiation from the sky that isBackground radiation from the sky that is
isotropic (same strength in all directions)isotropic (same strength in all directions)
 Corresponds to a temperatureCorresponds to a temperature
of just 2.7 Kelvinsof just 2.7 Kelvins
 Identified as the radiation leftIdentified as the radiation left
over from the Big Bang explosionover from the Big Bang explosion
Arno Penzias (right) and Robert Wilson
of Bell Laboratories, next to the horn
antenna with which they discovered the
CMB in 1965

11. Tests of the Big Bang TheoryTests of the Big Bang Theory
 Expansion of the universeExpansion of the universe
 Cosmic microwave backgroundCosmic microwave background
 Relative abundancesRelative abundances
of hydrogen,of hydrogen,
deuterium,deuterium,
helium and lithium

12. Obtaining the Age of theObtaining the Age of the
UniverseUniverse
 Extrapolate the current expansion rateExtrapolate the current expansion rate
(Hubble constant)(Hubble constant) back to the Big Bangback to the Big Bang
• 10 to 20 billion years old10 to 20 billion years old
 Look for the oldest starsLook for the oldest stars
(in globular clusters)(in globular clusters)
• 11 to 18 billion years old11 to 18 billion years old
 Best current estimate isBest current estimate is
13.4 ± 1.6 billion years13.4 ± 1.6 billion years
M10 Globular Cluster

13. Summary: Timeline of theSummary: Timeline of the
UniverseUniverse

14. Timeline of the Universe 2Timeline of the Universe 2

15. The Big Bang TheoryThe Big Bang Theory
 The violent expansion of anThe violent expansion of an
extremely small, hot, and denseextremely small, hot, and dense
body of matter between 12 and 18body of matter between 12 and 18
bya (billion years ago).bya (billion years ago).

16. Major EvidenceMajor Evidence
1.1. We are reasonably certain that theWe are reasonably certain that the
universe had a beginning.universe had a beginning.
2.2. Galaxies seem to be moving apartGalaxies seem to be moving apart
from each other.from each other.
3.3. We have found remnants of the heatWe have found remnants of the heat
believed to be from the big bang.believed to be from the big bang.
4.4. The abundance of hydrogen andThe abundance of hydrogen and
helium in the universe seems tohelium in the universe seems to
support the theory.support the theory.

17. Big Bang TimelineBig Bang Timeline
1.1. The universe began with anThe universe began with an
expansion of all the matter andexpansion of all the matter and
energy of the universe.energy of the universe.
2.2. The universe begins to cool off.The universe begins to cool off.
3.3. Gravity begins to take effect andGravity begins to take effect and
subatomic particles form.subatomic particles form.
4.4. The basic elements (hydrogen andThe basic elements (hydrogen and
helium) form.helium) form.

18. Big Bang TimelineBig Bang Timeline
1.1. As the enormous cloud of hot gasAs the enormous cloud of hot gas
cools electrons fuse with the basiccools electrons fuse with the basic
elements to make heavier elements.elements to make heavier elements.
2.2. Stars begin to form and galaxies areStars begin to form and galaxies are
formed.formed.
3.3. Stars are starting to die and puttingStars are starting to die and putting
heavier elements into space.heavier elements into space.
4.4. Heavier elements combine to formHeavier elements combine to form
planets that orbit a central star.planets that orbit a central star.

20. Fusion of StarsFusion of Stars
 Smaller nucleiSmaller nuclei
collide andcollide and
fuse releasingfuse releasing
a large amounta large amount
of energy andof energy and
creatingcreating
heavierheavier
elements.elements.

22. Elements up to the weight of
iron are manufactured in stars.
Elements heavier than iron are
formed when a supernova
explodes.

23. These gaseous supernova remnants glow
in colors determined by the elements they
contain. For example, the dark blue areas
are rich in oxygen and the red material is
rich in sulfur.
Orion nebula, a
region of intense
star formation.
Much of the brightness in
this infrared view of the
Horsehead nebula comes
from PAH emissions.
The Cat's Eye
Nebula has an
AGB star at its
center.

24. Composition of the UniverseComposition of the Universe
 Not StaticNot Static
 Different areas of the Universe haveDifferent areas of the Universe have
different compositions.different compositions.
 Mostly Hydrogen and HeliumMostly Hydrogen and Helium

25. Composition of the EarthComposition of the Earth
Element found in the Earth’s atmosphere
Elements found on Solid Earth

26. Composition of the SunComposition of the Sun

27. Most Common ElementsMost Common Elements
 UniverseUniverse
1.1. HydrogenHydrogen
2.2. HeliumHelium
 EarthEarth
• Solid EarthSolid Earth
1.1. OxygenOxygen
2.2. SiliconSilicon
• Earth’s AtmosphereEarth’s Atmosphere
1.1. NitrogenNitrogen
2.2. OxygenOxygen