Hi guys, I'm in a pickle here with an assignment, hope someone can help...greatly appreciated in advance.(adsbygoogle = window.adsbygoogle || []).push({});

I'm required to find the redshift at which the energy density in radiation equals the energy density in matter.

The following are the givens we were...well, given:

1) assume 1 baryon = 10^9 photon

2) assume all photons have energy to the wavelength of the peak of a 2.73K black-body radiation curve

3) scale factor (a) of matter: Pm = a^-3

4) scale factor of radiation: Pr = a^-4

5) we are to work out the energy density of a photon & baryon in present time and then apply the scale factor

Apparently this isn't using complicated formulas, just simple E=mc^2 & E=h*nu...but being an economic student, you can say I'm pretty lost. I'm sure it's something simple that I'm just not seeing.

Please help, any would be good.

Thanks in advance

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# Calculating Energy density in matter & radiation

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