Evidence for Big Bang

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Evidence for Big Bang

Whats that white stuff?
Observed by Arno Penzias and Robert Wilson
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Some galaxies
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Distribution in space

• Galaxies grouped in clusters

M. Colless, ANU
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Heres a pretty one! But what would it look like
if we lived in it?
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Milky Way

• Band of light and across sky
• Ancient ideas
• River (Nile, Ganges)
• Sacrificial or heavenly smoke
• Snowy path of the great Raven
• Milk of Hera after forcing nursing baby Hercules
  away
• Path souls take in afterlife
• Candy bar

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Milky Way

• Structure
• Spiral Arms WAVES!!
• Star forming regions
• Central bulge
• Halo of older stars

• Size
• Mass 1012 Msun
• 20-40 in stars
• 600 trillion miles across
• Sun 1/3 of the way from center
• Rotation 200 x 106 years

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What makes us think everything is rushing out
from an explosion? Galaxies are moving away from
us and from one another How did people measure
the speed? We need to have a little talk about
LIGHT. Light travels to us from the stars in the
distant galaxies. Light travels as a WAVE
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Here are some waves. What is wavelength?
What is frequency? Does water flow along with
the waves?
http//chair.pa.msu.edu/applets/doppler/a.htm http
//www.lon-capa.org/mmp/applist/doppler/d.htm
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Light is an electromagnetic wave -- HERE ARE
IMPORTANT FACTS! In light, Color
wavelength violet is short, red is long
(1/1000 of an mm) There are wavelengths
longer and shorter than what our eyes can
see. e.g. IR is a little longer, radio waves
are long, x-rays are short, but
all are the same except for wavelength Amazing
coincidence Sun-light after getting through the
air matches what our eyes can see! Speed of
these general light waves is constant, no matter
what wavelength Group activity What happens
to the frequency if wave length gets longer?
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Light is an electromagnetic wave In light,
Color wavelength violet is short, red is
long (1/1000 of an mm) There are wavelengths
longer and shorter than what our eyes can
see. e.g. IR is a little longer, radio waves
are long, x-rays are short, but
all are the same except for wavelength Amazing
coincidence Sun-light after getting through the
air matches what our eyes can see! Speed of
these general light waves is constant, no matter
what wavelength Group activity What happens
to the frequency if wave length gets
longer? Group activity What happens to the
frequency if you are moving away from the source?
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http//chair.pa.msu.edu/applets/doppler/a.htm
Or http//www.lon-capa.org/mmp/applist/doppler/d.
htm

• Doppler Shift
• Approaching object waves change frequency
• Examples
• Race cars (sound)
• Train whistle (sound)
• Police radar (microwave)
• Weather radar (microwave)
• Mapping galaxies (visible light)

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Motion of galaxies

• How do you measure it?
• Doppler Shift

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Galaxies are redshifted!

• In 1910s at Lowell Observatory in Flagstaff,
  Arizona, Vesto Slipher was the first to measure
  the redshift of a spiral nebula (now known as a
  galaxy).
• Slipher realized that the redshift of the
  spectrum of the spiral nebula (galaxy) meant that
  it was moving away from us at a very high speed.

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But how does this show that everything came out
of one big bang? Activity Cars! Activity Age
of the Universe!
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• Galaxies are moving away from us.
• Galaxies that are further away are moving faster.
• The universe is expanding!

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So a Big Bang Flash of light from the
explosion background radiation -- TV and radio
static!! (remember light and radio are the same
thing) 13.7 Billion years back! The explosion
would create hydrogen and helium and lithium, in
roughly the amounts that we know exist, but
other substances were produced later in a
different way. What did the explosion expand
into Nothing, not even space. How weird is
that? Penzias/Wilson/Dicke story
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Evidence for Big Bang

Observed by Arno Penzias and Robert Wilson