What was the temperature of the universe when a typical CMB photon was no longer able to spontaneously create an electron and positron pair? Note that a photon has an energy equal to E = hc/λ,the CMB at any point in time has a blackbody spectrum that peaks at a wavelength λ_peak = (2900 μm K)/T,and the mass of a single electron is 9 × 10⁻³¹ kg. A)2000 K B)400,000 K C)2 million K D)40 million K E)2 billion K

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The Answer of What was the temperature of the universe when a typical CMB photon was no longer able to spontaneously create an electron and positron pair? Note that a photon has an energy equal to E = hc/λ,the CMB at any point in time has a blackbody spectrum that peaks at a wavelength λ_peak = (2900 μm K)/T,and the mass of a single electron is 9 × 10⁻³¹ kg. A)2000 K B)400,000 K C)2 million K D)40 million K E)2 billion K

What Was the Temperature of the Universe When a Typical