# Planck black-box radiation and the universe

1. Aug 18, 2006

### hurk4

As a result of my thread about local coordinates, frames distances, calculators etc. , I proceed now with this one about Planck blackbox radiation. I do this because I did not want to disturb other threads where I eventually could fit this in. Because it still has something to do with calculators I would be very greatful if hellfire could react.

- Physicists know that a black box with a defined wall temperature Te sends out E-M radiation through a small hole with a radiation temperature Te. It is also known that the radiation spectrum has the well defined Planck spectrum normalized according to its top temperature Te.
- The CMB radiation we receive has a radiation temperature of 2.728K, equivalent to a Planck radiation out of a black box with a wall temperature of 2.728K.
But now the radiation wavelength is the result of a radiation which was (Hubble) red shifted during it travel through the universe by a factor 1+z, z being the quotient of the emission temperature and the detected temperature here.
- Until yesterday morning I had at least one serious problem, I thought (wrongly?) that space it selves was radiating so that the received radiation should have the integrated result of radiation along its path. I could then not understand why the received radiation had just the pure 2.728 Planck spectrum, it has, while being the result of an integration of spectra, red-shifted from z=1101 to z=0.
- Then, driving my car, I came to the conclusion that, since long, space along the radiation path does not radiate at all, the received spectrum must be just the red shifted spectrum of the radiation with, roughly, T=3000K. I suppose I am right now?
- A second problem I have is: It seems strange and unbelievable to me that this emitted radiation had its origin just at the shell of the observed universe; it must come from farther away so where does it come from?
- Then the answer, as far as I heard, is: it comes from the last scattering surface at a temperature of T=3000K. (PM: according to the cosmological principle, such a surface is of course a virtual surface around us due to the restricted constant speed of light.)
- An additional question, the one of a kind I always had, with Planck-radiation is:
Coming from a (non physical?) wall, knowing that emission spectra are line spectra and that the individual lines are attached to specific particles, how can then just only some special particles like protons, neutrons, quarks provide us with such a nice full real Planck-spectrum?
- Indeed radiation could not travel freely until the temperature of its surrounding universe was cooled down to that temperature so that it not immediately became captured by existing particles. Then my question is why is that temperature so low where as we still receive radiation from the surface of our sun which has a temperature far above 5000K?
- But ok I suppose this can be well explained. Fact is, I suppose, that once radiation was generated at a much higher temperature of billions K; the universe around our BB then was really radiating. That radiation cooled down end red shifted during the Hubble expansion and finally could travel freely from its last-scattering-phase-area towards us.
- As long as there was particle-radiation interactivity I suppose that existing radiation did not cool down nicely according to Hubble expansion, so calculators only having algorithms based on Hubble’s-law will not give the correct answers.
- Further back in time when quantum effects are coming into play again new algorithms, (avoiding singularity) must be added in a calculator model, I suppose and I think, here we are in the quantum-gravity area where LQC, string theory, twistor-theory will lead us in a pre-bang situation which I feel will possibly have every thing to do with e.g. name it, multi-verse, omni-verse, Giga-verse, hyper-verse, Google-verse, infinity-verse.

2. Aug 22, 2006

### hurk4

My conclusion that space is not radiating because its radiation would mismatch CBR Planck-spectrum will probably be not right. Now, it seems well possible to me that the local radiation temperature of space is exactly equal the local temperature of the cooled down penetrating CBR.
- On the other hand if locally the received radiation would be equal to the send-out radiation then there will be no net radiation generated and the idea that space is generating radiation might be fault for that other reason.
- After all, based on red-shift alone, it seems not possible to me to calculate a distance from receiver to emitter if one does not know the emission-temperature of the emitter.
- Is the emitting temperature of the CBR really ~3000K?

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