Electromagnetic Spectrum

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

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.

Redshift: Definition

Star at rest:

Star moving away:

Photon looks normal

Photon looks redder

(Alternately: Wavelength is normal)

(Alternately: Wavelength is longer)

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

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)

Galaxy UGC 12915

Galaxy KUG 1750

Galaxy IRAS F09159

Redshift Riot

Complete the worksheet …

Red Shift Riot

€

20 , 000 −0109 −0

=183km

sMYr

BRHS10

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 !

Expansion of the Universe

We are NOT at the center of the Universe with galaxies flying through the Universe in all directions

Expansion of the Universe

• Space itself is expanding

• Objects are not

THEN

NOW

Redshift Riot

• Bungee Universe Demo• Do “Expansion” worksheet

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