Cosmic Microwave Background Hamza Meel December 4, 2019
Cosmic Microwave Background Table of Contents History First Experimental Evidence Modern Observations The Universe Before Recombination An Orange Plasma Acoustic Waves Inhomogeneity Results in Anisotropy Power Spectrum Conclusion
Cosmic Microwave Background History Table of Contents History First Experimental Evidence Modern Observations The Universe Before Recombination An Orange Plasma Acoustic Waves Inhomogeneity Results in Anisotropy Power Spectrum Conclusion
Cosmic Microwave Background History First Experimental Evidence A. Penzias’ and R.Wilson’s Observation ◮ 1964 ◮ Super-sensitive microwave antenna. ◮ Noise that can’t be removed. https://cosmology.education/images/holmdel_antenna.jpg
Cosmic Microwave Background History First Experimental Evidence A. Penzias’ and R.Wilson’s Observation ◮ 1964 ◮ Super-sensitive microwave antenna. ◮ Noise that can’t be removed. ◮ Matches R. Dicke’s predictions. https://upload.wikimedia.org/wikipedia/en/c/cf/Robert_Henry_ Dicke.jpg
Cosmic Microwave Background History First Experimental Evidence A. Penzias’ and R.Wilson’s Observation ◮ 1964 ◮ Super-sensitive microwave antenna. ◮ Noise that can’t be removed. ◮ Matches R. Dicke’s predictions. https://i.huffpost.com/gen/1853981/thumbs/ o-ROBERT-WILSON-PENZIAS-900.jpg
Cosmic Microwave Background History Modern Observations Most Known Missions ◮ COBE (1989 - 1993) https://science.nasa.gov/missions/cobe
Cosmic Microwave Background History Modern Observations Most Known Missions ◮ COBE (1989 - 1993) ◮ WMAP (2001 - 2010) https://www.nasa.gov/feature/ making-sense-of-the-big-bang-wilkinson-microwave-anisotropy-probe
Cosmic Microwave Background History Modern Observations Most Known Missions ◮ COBE (1989 - 1993) ◮ WMAP (2001 - 2010) ◮ Planck (2009 - 2013) http://www.esa.int/ESA_Multimedia/Images/2013/03/Planck_CMB
Cosmic Microwave Background History Modern Observations First peak in the power spectrum measured by: ◮ Toco ◮ BOOMEranG ◮ MAXIMA
Cosmic Microwave Background The Universe Before Recombination Table of Contents History First Experimental Evidence Modern Observations The Universe Before Recombination An Orange Plasma Acoustic Waves Inhomogeneity Results in Anisotropy Power Spectrum Conclusion
Cosmic Microwave Background The Universe Before Recombination An Orange Plasma An Artist’s Illustration of the Early Universe Color calculated by http://www.vendian.org/mncharity/dir3/blackbody/
Cosmic Microwave Background The Universe Before Recombination An Orange Plasma Characteristics of the Plasma ◮ Hot Plasma ( > 3000 K) ◮ Opaque due to Thomson scattering and electromagnetic interactions.
Cosmic Microwave Background The Universe Before Recombination An Orange Plasma Recombination ◮ Universe becomes cooler due to its expansion. ◮ 3000 K : Threshold for formation of hydrogen and helium.
Cosmic Microwave Background The Universe Before Recombination Acoustic Waves Origin of Acoustic Waves ◮ The plasma is moved by two forces: ◮ Gravity (attractive) ◮ Radiation pressure (repulsive) ◮ Formation of a pressure wave, also known as acoustic wave.
Cosmic Microwave Background The Universe Before Recombination Acoustic Waves Fundamental Problem Why should gravity be important ?
Cosmic Microwave Background The Universe Before Recombination Acoustic Waves Fundamental Problem ◮ Why should gravity be important ? ◮ Assuming the early universe to be uniform seems reasonable. ◮ Uniformity = ⇒ No potential wells = ⇒ No gravity
Cosmic Microwave Background The Universe Before Recombination Acoustic Waves The Solution: Quantum Noise ◮ Early quantum noise amplified by Inflation ◮ It creates inhomogeneities at all scales
Cosmic Microwave Background The Universe Before Recombination Acoustic Waves The Solution: Quantum Noise ◮ Early quantum noise amplified by Inflation ◮ It creates inhomogeneities at all scales = ⇒ Potential wells
Cosmic Microwave Background Inhomogeneity Results in Anisotropy Table of Contents History First Experimental Evidence Modern Observations The Universe Before Recombination An Orange Plasma Acoustic Waves Inhomogeneity Results in Anisotropy Power Spectrum Conclusion
Cosmic Microwave Background Inhomogeneity Results in Anisotropy From Inhomogeneity to Anisotropy ◮ At Recombination, the sound waves freeze. ◮ Imagine being in a well. 1. The light that we observe is also from the well = ⇒ isotropy.
Cosmic Microwave Background Inhomogeneity Results in Anisotropy From Inhomogeneity to Anisotropy ◮ At Recombination, the sound waves freeze. ◮ Imagine being in a well. 1. The light that we observe is also from the well = ⇒ isotropy. 2. Some part of the light we observe is now from a hill.
Cosmic Microwave Background Inhomogeneity Results in Anisotropy From Inhomogeneity to Anisotropy ◮ At Recombination, the sound waves freeze. ◮ Imagine being in a well. 1. The light that we observe is also from the well = ⇒ isotropy. 2. Some part of the light we observe is now from a hill. 3. Well, hill, well.
Cosmic Microwave Background Inhomogeneity Results in Anisotropy From Inhomogeneity to Anisotropy ◮ At Recombination, the sound waves freeze. ◮ Imagine being in a well. 1. The light that we observe is also from the well = ⇒ isotropy. 2. Some part of the light we observe is now from a hill. 3. Well, hill, well. 4. Well, hill, well, hill.
Cosmic Microwave Background Inhomogeneity Results in Anisotropy From Inhomogeneity to Anisotropy ◮ At Recombination, the sound waves freeze. ◮ Imagine being in a well. 1. The light that we observe is also from the well = ⇒ isotropy. 2. Some part of the light we observe is now from a hill. 3. Well, hill, well. 4. Well, hill, well, hill. 5. Et caetera ◮ http://background.uchicago.edu/~whu/intermediate/brief.gif
Cosmic Microwave Background Power Spectrum Table of Contents History First Experimental Evidence Modern Observations The Universe Before Recombination An Orange Plasma Acoustic Waves Inhomogeneity Results in Anisotropy Power Spectrum Conclusion
Cosmic Microwave Background Power Spectrum Definition ◮ Power spectrum of a signal is the Fourier transform of its magnitude squared. ◮ Multipoles l are used in place of wave-numbers k .
Cosmic Microwave Background Power Spectrum Existence of Harmonics ◮ Inflation amplified noise to all scales. ◮ If a mode exists, its harmonics too.
Cosmic Microwave Background Power Spectrum Extrema of Vibrations ◮ There exist a mode such that it only went through one compression.
Cosmic Microwave Background Power Spectrum Extrema of Vibrations ◮ There exist a mode such that it only went through one compression. ◮ So there exist one who went through a compression and a relaxation, and so one
Cosmic Microwave Background Power Spectrum Extrema of Vibrations ◮ There exist a mode such that it only went through one compression. ◮ So there exist one who went through a compression and a relaxation, and so one ◮ Baryons help compression but not relaxation.
Cosmic Microwave Background Power Spectrum First Peak of the Power Spectrum ◮ The multipole moment l 1 of the first peak depends on the curvature of the universe. ◮ The more negative the curvature, the higher is l 1 . Three-Year Wilkinson Microwave Anisotropy Probe (WMAP*) Observations: Temperature Analysis, G.Hinsaw et al., The American Astrophysical Journal Supplement Series, 2007, https://doi.org/10.1086/513698
Cosmic Microwave Background Power Spectrum First Peak of the Power Spectrum ◮ The multipole moment l 1 of the first peak depends on the curvature of the universe. ◮ The more negative the curvature, the higher is l 1 . ◮ Measurements on CMB indicates a (nearly) flat universe. Three-Year Wilkinson Microwave Anisotropy Probe (WMAP*) Observations: Temperature Analysis, G.Hinsaw et al., The American Astrophysical Journal Supplement Series, 2007, https://doi.org/10.1086/513698
Cosmic Microwave Background Power Spectrum First Peak of the Power Spectrum ◮ The multipole moment l 1 of the first peak depends on the curvature of the universe. ◮ The more negative the curvature, the higher is l 1 . ◮ Measurements on CMB indicates a (nearly) flat universe. ◮ We do not observe enough matter and dark matter to have a flat universe. Three-Year Wilkinson Microwave Anisotropy Probe (WMAP*) Observations: Temperature Analysis, G.Hinsaw et al., The American Astrophysical Journal Supplement Series, 2007, https://doi.org/10.1086/513698
Cosmic Microwave Background Power Spectrum First Peak of the Power Spectrum ◮ The multipole moment l 1 of the first peak depends on the curvature of the universe. ◮ The more negative the curvature, the higher is l 1 . ◮ Measurements on CMB indicates a (nearly) flat universe. ◮ We do not observe enough matter and dark matter to have a flat universe. ◮ This missing energy is called dark Three-Year Wilkinson Microwave Anisotropy Probe (WMAP*) Observations: Temperature Analysis, G.Hinsaw et al., The American Astrophysical Journal Supplement Series, 2007, energy . https://doi.org/10.1086/513698
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