Wikipedia: Olbers paradox/Talk

Is this a paradox ? - anon

I know nothing about this, but might not another explanation be that there is so much dust and gas in the universe that light from very different stars is so dim as to be imperceptible, because it is absorbed along the way? Even in a non-expanding universe, you wouldn't expect very very distant stars to be visible anyway... -- Simon J Kissane

I'm not quite clear about the meaning and correctness of the article's last paragraph. Wouldn't thermodynamics forbid us to recycle radiation into matter? --AxelBoldt

Also, I take it that electromagnetic radiation is converted to kinetic energy (heat) all the time. Why should we postulate a hypothetical method for transferring electromagnetic radiation into matter, when there's another observable explanation for how electromagnetic radiation can be converted into another kind of energy? Beyond that if the universe is not bounded, or if it is expanding there's no reason to believe that anything has to happen to the light -- it can just continue to disperse. (But I am certianly no expert in this field...) MRC

With regard to Axel's question: radiation is routinely converted into matter in particle accelerators: most commonly into electron/positron pairs. This is called pair production. The only problem with such recycling is that known methods of matter production result in equal quantities of matter and antimatter, which is not what is observed in nature. Thermodynamics does not forbid recycling. However, it does suggest that a state of equilibrium will eventually be reached, and maintained thereafter. If there is no conversion of energy into matter then the equilibrium state will probably be one in which all except a small remnant of matter has been converted into energy in the form of radiation.

With regard to MRC's points: Yes, EM radiation is converted into kinetic energy. If this were to take place e.g. in a hydrogen gas cloud, some of the kinetic energy would be converted back into low temperature radiation (radio waves). Somebody has already added a paragraph to the main article regarding this possibility, saying that "it would result in strong radiation which is not observed". This also seems to address Simon Kissane's point. However, *some* radiation from gas clouds most certainly is observed.

With regard to light becoming increasingly dispersed in an expanding universe - this is partly covered by the statement about light becoming increasingly redshifted and diminished in brightness in such a universe. However, increasing separation between photons as a possible cause of diminished brightness should perhaps have an explicit mention.

I'll refrain from modifying the main article any further, because I personally favour the idea that energy is recycled into matter, and I find it difficult to evaluate other possibilities objectively.

--Martin Gradwell.