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Loren Booda
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What is the cross section of a photon traversing the observable universe? That of a neutrino? Dark matter in general?
Loren Booda said:What is the cross section of a photon traversing the observable universe? That of a neutrino? Dark matter in general?
hurk4 said:If no mass can be attached to a photon I think it should be infinite because of its Compton-lenght which is inversely proportional to it mass.
But if due to E=mc^2= hf, kind of equivalend mass can be attached to a foton then fill this mass in into the Compton-lenght formula and you will find the order of magnitude of this dimension.
Personnaly I am not a specialist (but curious for an answer) who could answer your question, I hope there will be one who will do so.
Kind regards
Loren Booda said:hurk4,
Indeed, now that I study it, I do see a nontrivial duality between the mass-characteristic length (Compton wavelength, h/mc - traditionally infinite for the photon) and the EM-characteristic length (E/hc, where E here is the electromagnetic energy of the photon).
One might say that the former is more a property belonging to the wavefunction of quantum mechanics, while the latter deals with spacetime and charge as well. I believe charge endows spacetime with an non-zero mass-energy (finite wavelength), although an EM wave in vacuo is of infinite extent.
Loren Booda said:Theoretically at least, Hawking radiation does tunnel "out" of a black hole.
Would you please show your calculation for the Compton length (and its equivalent) of a CBR photon?
Loren Booda said:hurk4,
although an EM wave in vacuo is of infinite extent.
Loren Booda said:hurk4,
I am beginning to believe that the cross section mentioned in the topic above is intimately involved with the cosmological constant, of inverse area units cm-2.
hurk4 said:Loren Booda
Eventually I can see that a photon looses (?) energy (equivalent with a (loss) of mass) inverse with its Compton-dimension
kind regards Hurk4
Loren Booda said:hurk4,
How did you come up with the figure of 5.26*10^65 meters? It seems many orders of magnitude too much. Try 5.27*10^-3 meters. Think "microwave background"!
Due to the Higgs potential condensing to a real vacuum, particles may or may not gain mass over their virtual, massless states. Since a photon is massless whether in a true or false vacuum, it would still have an infinite range.
Yes, but such a curvature effect is also convoluted with an expansion effect.Loren Booda said:Folks,
Open, closed and flat spacetimes differ in the angular projection of geodesics progressing from observer to horizon. Such differences in possible solid angles define differences in the spread of light rays, in turn determining divergent cross sections for photon events. Could similar phenomena be used (or are they already?) to measure the curvature of the universe?
The middle solid curve is for ([itex]\Omega_M[/itex],[itex]\Omega_{\Lambda}[/itex] = (0,0). Note that this plot is practically identical to the magnitude residual plot for the best-fit unconstrained cosmology of Fit C, with ([itex]\Omega_M[/itex],[itex]\Omega_{\Lambda}[/itex]) = (0.73,1.32).
Theoretical models predict that the initial metallicity of the progenitor of a Type Ia supernova (SN Ia) affects the peak of the supernova light curve. This can cause a deviation from the standard light curve calibration employed when using SNe Ia as standardizable distance candles and, if there is a systematic evolution of the metallicity of SN Ia progenitors, could affect the determination of cosmological parameters.
The cross section of a photon is a measure of the area that is likely to interact with a particular target particle or system. It is typically represented by the symbol σ and is measured in units of area, such as square meters.
When we say a photon is traversing the observable universe, it means that the photon is traveling through the vast expanse of space that can be observed from Earth. This is estimated to be a diameter of about 93 billion light-years.
The cross section of a photon determines the likelihood of it interacting with matter in the observable universe. A larger cross section means a higher chance of interaction, while a smaller cross section means a lower chance of interaction.
The cross section of a photon can be affected by various factors such as its energy, the type of particle or system it is interacting with, and even the distance it is traveling.
Studying the cross section of a photon is important because it allows us to better understand how photons interact with matter and how they contribute to the structure and evolution of the observable universe. It also helps us make predictions and test theories about the behavior of particles and systems in the universe.