The discussion focuses on estimating the number of Cosmic Microwave Background (CMB) photons in a 0.25-litre volume using the energy density formula for blackbody radiation, E = 4σ/C * T^4. Participants recommend using the photon gas Wikipedia page and Barbara Ryden's textbook, which states there are approximately 411 CMB photons per cubic centimeter in the universe today. To derive the number of photons, one can apply Planck's Law and the relationship E = hv, where v represents frequency.
PREREQUISITESAstronomers, physicists, and students studying cosmology or thermodynamics who seek to understand the properties and calculations related to Cosmic Microwave Background radiation.
Frimus said:I recommend a textbook by Barbara Ryden https://www.amazon.com/dp/1107154839/?tag=pfamazon01-20. In section "2.5 Cosmic Microwave Background" she makes calculations you are asking about and comes to a conclusion that "...there are about 411 CMB photons per cubic centimeter of the universe at the present day."
Chalnoth said:This link might help:
https://en.m.wikipedia.org/wiki/Photon_gas
If you want to drive the result yourself, use E=hv for the energy of a photon of a given frequency to do the appropriate integral.
I'm not sure what level the question is being asked. The photon gas wiki page has the number of photons per volume as a function of temperature directly. You could just use that formula and get the answer straight away.rano jojo said:Thank you, but i how i can get the frequency and then how i can find the number of the photons? just i am confused
Use E=mc^2 n another relation in which uses T of this relation~rano jojo said:i know that the total energy density of a blackbody radiation is
E= 4 segma/C * T^4
so how i can use this to find the number of the CMB photons in 0.25 litre?