The Cosmic Microwave Background Radiation Mitchell Pearsall Colorado

The Cosmic Microwave Background Radiation Mitchell Pearsall, Colorado College What is the CMB? The Cosmic Microwave Background Radiation (CMB) is the first light in the universe. No matter how far away we look or how deep we peer in the past, it is the last thing we see. Simply put, the CMB is the boundary of the visible universe. What released the CMB? If the early universe was opaque, how can we see the CMB? The CMB was released when the early universe became cool and diffuse enough for the first atoms to coalesce. Photons could now traverse and space and time unimpeded by subatomic particles. This event is called Recombination. The CMB as a Blackbody The CMB is nearly a perfect blackbody which means it emits electromagnetic radiation as a function of its temperature. This characteristic temperature of the CMB can be deduced from the wavelength of light we receive from it (160 GHz). Using the Planck Equation, one can derive its temperature (2. 73 Kelvin). The BAOs introduce some fluctuation from this temperature due to the over and underdensities they create. The Planck equation which expresses intensity (uν) as function of temperature (T) and frequency (ν). ( A graph of a variation of this equation is included below. A map of the CMB. The CMB is present everywhere in the sky and has a constant distance to us, thus it looks like sphere. The photo above is a 2 -D projection of the CMB. Red and blue spots show different wavelengths of light. Credit: European Space Agency What caused the CMB? The early universe before the CMB was a hot, dense plasma. Light couldn’t travel very far before bumping into sub atomic particles, diverting its path. The early universe was opaque in this regard. This is why we cannot see past the CMB. A photon (black lines) released from the plasma of the early universe after recombination. Recombination occurs at the boundary between the yellow and green areas of the graphic. Credit: University of Oregon- Cosmic Microwave Background Wavelength Deviations in the CMB The light from the CMB has different wavelengths. This is caused by the Baryon Acoustic Oscillations (BAO). BAOs were areas of over and under densities propagating through the plasma of the early universe. Since temperature can be thought of as the average kinetic energy of particles, the BAOs introduce are small temperature fluctuations(+/-. 00057 Kelvin from the average temperature). BAOs became ‘frozen’ at Recombination. A graph of frequency versus energy density. The frequencies of the CMB are graphed in red (measurements made by the COBE satellite). The frequencies of an ideal blackbody (described by the Planck equation) are graphed in green. Credit: Wikipedia - Quantum Doughnut Acknowledgments Thanks to Dr. Shane Burns for assisting me with understanding this topic in depth. Thanks to Dr. Stephanie Di. Cenzo for teaching Colorado College physics majors how to present science in a clear and concise manner. Image References: A photon (black lines) being deflected from its trajectory by protons and electrons (red and blue circles) in the plasma of the universe. Credit: University of Oregon- Cosmic Microwave Background The force of gravity creates overdensities and the force of the electromagnetic radiation pressure creates underdensities. The propagation of these density fluctuations create the temperature fluctuations we see in the CMB. Credit: University of Chicago- Wayne Hu What is the CMB: https: //www. esa. int/Science_Exploration/Space_Science/Planck_and_the_cosmi c_microwave_background What caused the CMB? / What released the CMB? : http: //abyss. uoregon. edu/~js/21 st_century_science/lectures/lec 27. html Temperature Deviations in the CMB: http: //background. uchicago. edu/~whu/intermediate/gravity. html Features of the CMB: https: //en. wikipedia. org/wiki/Cosmic_microwave_background#/media/File: Cmbr. svg