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Electromagnetic Spectrum
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Element Spectrum
• Each element has a spectral “fingerprint” — a pattern of bright or dark lines that is UNIQUE to that element.
• Pay attention — there’s a quiz …
Which element am I?RUBIDIUM
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Redshift: DefinitionLight from our Sun:
Light from a star or galaxy moving away from us: WHAT’S DIFFERENT?WHAT’S DIFFERENT?
Low Energy Photons
High Energy Photons
The size of the redshift tells us
the speed of the star or
galaxy
Photons lose energy and
become more red if the star is moving
away from us.
Photons of all energies (colors)
Specific elements in atmosphere of
star absorb specific photon energies,
leaving black lines.
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Redshift: Definition
Star at rest:
Star moving away:
Photon looks normal
Photon looks redder
(Alternately: Wavelength is normal)
(Alternately: Wavelength is longer)
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MOVING AWAY
Redshift: Calculation
Egalaxy = energy of photon from a galaxy that’s moving away
Erest = energy of photon from a star that’s not moving
€
redshift =Erest −Egalaxy
Egalaxy
€
velocity of galaxy= redshift × speed of light
AT REST
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Redshift: Real DataVINTAGE VERSION: Spectra recorded on photographic plates. These spectra show shifts in a hydrogen line compared to the laboratory (at rest) spectrum.
MODERN VERSION: Fiber optic scanning and full digital spectrum plots (from the Sloan Sky Survey)
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Galaxy UGC 12915
Galaxy KUG 1750
Galaxy IRAS F09159
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Redshift Riot
Complete the worksheet …
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Red Shift Riot
€
20 , 000 −0109 −0
=183km
sMYr
BRHS10
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Redshift: Interpretation
• We can measure redshift
• Redshift means galaxy is moving away
• All galaxies (except our nearest neighbors) are redshifted
• All galaxies are moving away
• Therefore, the universe is EXPANDING
SCIENTISTS ARE NOT GUESSING !
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Expansion of the Universe
We are NOT at the center of the Universe with galaxies flying through the Universe in all directions
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Expansion of the Universe
• Space itself is expanding
• Objects are not
THEN
NOW
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Redshift Riot
• Bungee Universe Demo• Do “Expansion” worksheet
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What is the Universe expanding into?
• The Universe is expanding into nothing• EMPTY SPACE is still something and has a here, a there, distances and time.
• NOTHING has no here, no there, no distance, and no time.
Here
There
distancetime