Timeline for What is the current value for the temperature at which Recombination took place?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
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| Nov 7, 2018 at 22:04 | comment | added | ProfRob | As I explained, you don't "know" the current value. It is $\Omega_b$ times the critical density. | |
| Nov 7, 2018 at 21:49 | comment | added | user32023 | @RobJeffries - Redshift is model independent. If I know the temperature now (2.75K) I can determine the temperature at z=1090 by the formula $T = T_0(1+z)$. Why can't I do the same thing with the density of hydrogen if I know the present value: $(n_p+n_H)(z)=1.6(1+z)^3$? That would remove the Cosmological model from at least the Sound Horizion and Distance to LS calculations. | |
| Nov 7, 2018 at 21:36 | comment | added | ProfRob | The CMB is not a picture of the universe at some point in time. I have explained that the universe does not become transparent to the CMB at a single temperature. Neither can the estimate of what that range of temperatures is be entirely divorced from a model of what the baryonic density is as a function of redshift, since ionisation depends on temperature and density. The whole point of CMB studies is that CMB properties do depend on cosmological models and parameters. | |
| Nov 7, 2018 at 13:13 | comment | added | user32023 | I agree that the question appears to be confusing and that's related to my naive understanding of the subject matter. The CMB is a picture of the universe at some point in time. I want to know what the temperature of the universe was when that picture was created. If it's a range of values, then how do you accurately calculate the Sound Horizon and the distance to the Surface of Last Scattering? | |
| Nov 7, 2018 at 12:22 | comment | added | ProfRob | The 1090 number in that paper has a very specific meaning. It is the redshift at which the optical depth to Thomson scattering is 1 between now and that redshift. It is not the answer to the question you asked. It is the peak of the so-called "visibility function". Photons in the microwave background arrive at Earth from a range of redshifts. | |
| Nov 7, 2018 at 1:18 | history | answered | user32023 | CC BY-SA 4.0 |