Cosmic Music : Sounds from the Infant Universe - PowerPoint PPT Presentation

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Cosmic Music : Sounds from the Infant Universe

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  1. Cosmic Music : Sounds from theInfant Universe Mark Whittle University of Virginia

  2. Map of the universe & this talk We need to build a bridge from here to there : • Stars, galaxies, clusters, walls/voids  expansion • Ways to access the past : observe it directly (!) Our destination is the edge of the universe & the beginning of time. We can then : • Describe the initial fireball (seen as the CMB) • Unpack the sound waves, and listen to them !

  3. Properties of the Universe • Isotropic(same in all directions) • Homogeneous (same at all locations) • Expanding

  4. Hubble law tells us :the Universe ….. • Has no centre • Will get emptier in the future • Was denser in the past  its youth was very different • Was “all together” ~14 Byr ago  it was “born” in a Big Bang

  5. Uncovering the Past • Archeology infer the past from the present • 2. Watch History Now (?!?) • Astronomers have access to a natural time machine

  6. HDF

  7. expansion cooling Big Bang dense hot rarified cool Now ionized foggy 380,000 yr 3000 K hot glowing fog us redshift z=1000 The Microwave Background atomic transparent we see a glowing wall of bright fog orange light microwaves

  8. Human lifespan Conc- eption child teenage Old age 12hr Marathon race Finish 26 miles Start 4 feet CMB is Young and Far 380,000 yr 5 Time (Gyr) 10 0 14 Big Bang here now “nearby” galaxies CMB NGST HST

  9. Two ways to view patchiness • Seeds of cosmic structure : • Gravity amplifies density variations • peaks grow into clusters of galaxies • troughs grow into voids  computer models of structure formation • 2. Sound waves : • Peaks/troughs in pressure = sound waves • The “Big Bang” has both light and sound •  Acoustic analysis reveals cosmic properties

  10. Model evolution of this region Gravity amplifies density contrasts

  11. SDSS : ⅓ million galaxies More detailed similation 3 billion light years (~20% to “the edge”) Our galaxy is here

  12. Sound waves : red/blue = high/low gas & light pressure Many waves of different sizes, Directions & phases, all “superposed” Water waves : high/low level of water surface

  13. Nature of Cosmic Sound • Volume : • pressure variations ~ 1/100,000 • corresponds to about 90 dB • Loud but not cacophonous • Pitch : measured wavelengths 20,000 – 200,000 lyr pitch 10-12– 10-13 Hz (v ~ 0.6c)  48 – 52 octaves below concert A (440 Hz) • Quality: need to construct the “power spectrum”

  14. Power spectra Sounds are not usually just one frequency, many frequencies are simultaneously present. The relative amount (loudness) of each frequency is called the power spectrum. Thus sounds can be graphed in two ways : • waveform = pressure vs time (or location) • power spectrum = loudness vs frequency (pitch) Some examples :

  15. Baroque Baroque Modern