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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: Definition Specific elements in atmosphere of Light from our Sun: star absorb specific Photons of all energies (colors) photon energies, Low Energy Photons leaving black lines. High Energy Photons ThePhotons size of the lose redshift tells and us energy the speed of red if become more thestar starisormoving the Light from a star or galaxy moving away galaxy away from us. from us: WHAT’S DIFFERENT? Redshift: Definition Star at rest: Photon looks normal (Alternately: Wavelength is normal) Star moving away: Photon looks redder (Alternately: Wavelength is longer) Redshift: Calculation Erest = energy of photon from a star that’s not moving AT REST E rest E galaxy redshift = E galaxy velocity of galaxy = redshift speed of light MOVING AWAY Egalaxy = energy of photon from a galaxy that’s moving away Redshift: Real Data VINTAGE 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 km 20,000 0 s 183 109 0 MYr 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. Here distance time There • NOTHING has no here, no there, no distance, and no time.