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EEWannabe
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Homework Statement
Estimate the pressure of the CMB photons today. [You will need to choose a reasonable value for the present value of the temperature of the CMB. The radiation
constant is α = 7.56 × 10−15erg cm−3K−4
Assume that a new population of stars is discovered, and their age is estimated to
be 19 Gyr.
From this observational result, derive an (approximate) value for the Hubble
parameter today, and express the result in kms−1Mpc−1
First question . Energy Density = aT^4.
E(photon) = kT
2nd Question;
v = Hd
Hey there, I've left it too late again ! And I have an exam tomorrow so any hints on these ones would be great;
1) Taking the current temperature as 2.7K, the energy density from radiation can be worked out. However I don't really get it when it asks for the pressure? How exactly do I work that out? I've never seen anything like it. The energy of a single photon at 2.7K can be worked out using E = kT, but I don't see how that will help.
2) I don't understand this one at all, what does it mean 19Gyear? Giga years? If so that's older than the universe surely... Any points in the right direction here would be fantastic.
Estimate the pressure of the CMB photons today. [You will need to choose a reasonable value for the present value of the temperature of the CMB. The radiation
constant is α = 7.56 × 10−15erg cm−3K−4
Assume that a new population of stars is discovered, and their age is estimated to
be 19 Gyr.
From this observational result, derive an (approximate) value for the Hubble
parameter today, and express the result in kms−1Mpc−1
Homework Equations
First question . Energy Density = aT^4.
E(photon) = kT
2nd Question;
v = Hd
The Attempt at a Solution
Hey there, I've left it too late again ! And I have an exam tomorrow so any hints on these ones would be great;
1) Taking the current temperature as 2.7K, the energy density from radiation can be worked out. However I don't really get it when it asks for the pressure? How exactly do I work that out? I've never seen anything like it. The energy of a single photon at 2.7K can be worked out using E = kT, but I don't see how that will help.
2) I don't understand this one at all, what does it mean 19Gyear? Giga years? If so that's older than the universe surely... Any points in the right direction here would be fantastic.