Talk:Olbers's paradox

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A Thought Experiment

Let's perform a thought experiment. Assumed is the cosmological principle, that states the spatial distribution of matter in the universe is homogeneous and isotropic when viewed on a sufficiently large scale. We start to assume it is the light from stars that determine the brightness of the sky at night. We neglect e.g. the 2.7 K background radiation that did not origin in stars. Imagine you had a magic button that speeds up star evolution. With this button all molecular clouds in the universe immediately convert into stars and all stars (old ones and the newly formed) immediately convert entirely into radiation, according to E=mc². The situation cannot become worse. The resulting radiation bath or photon gas as it sometimes is called, when considered at scales large enough for the cosmological principle to become apparent, is uniform and thus in equilibrium with respect to the amount of photons per area. An area can only gain more radiation at the cost of nearby areas and that on the average will counteract statistics. Normally an area will radiate out to nearby areas the same amount as it receives from that areas. Mind the light of stars IS the radiation bath. The amount of radiation that enters a steradian in one second then is the brightness of the sky at night, that is, its upper limit. This is a finite amount and so this suffices as a solution of the Paradox of Olbers.

Mind this solution does not depend on the size of the universe, nor on its age, nor on whether the universe is expanding or not. That is, the considered areas must be large enough for the cosmological principle to become apparent. And the age must be sufficient long for light to have crossed that areas, allowing the photon bath in a single area to become uniform. But it is not important whether the size or age is finite or infinite. It only depends on the density of the universe. The solution works also for the Steady State cosmological model.

Of course expansion of the universe dilutes the radiation bath and lowers its average brightness. In the course of time from the Big Bang up to now the universe passes all densities from, well let's start at 10^17 kg/m³ (neutron star density) down to 10^-26 kg/m³ (critical density of the universe, that it is now, nearly). It depends on the precise moment in this elapse of time where you perform this thought experiment, what precisely is the value of the upper limit of the brightness of the sky at night.

Nowadays most molecular clouds have not yet contracted to stars, and not all star matter will finally convert to radiation. So, what is the actual radiation bath right now? The density of the universe as it is now consists of 73% Dark Energy, 23 % Dark Matter (WIMPs, neutrinos), 4 % ordinary matter (protons, neutrons, electrons) and only 0.005 % consists of photons (starlight and Background radiation). --87.210.223.62 (talk) 11:05, 31 August 2017 (UTC)

References

Really? The brightness gives an argument?

"Suppose that the universe were not expanding, and always had the same stellar density; then the temperature of the universe would continually increase as the stars put out more radiation."

"Suppose that the EARTH were not expanding, and always had the same MATTER density; then the temperature of the EARTH would continually increase as the EARTH gathers more radiation."

(1) Where is the radiation from? => There, where it comes from, there isn't it anymore!

(person asking this didn't sign but I'll start here) You're missing something very important. The Earth isn't a closed system. It continually loses energy to space (as radiation, in fact), and it's at an equilibrium (more or less), meaning temperature stays around the same. The difference between Earth and the stars is that, in stars, nuclear fusion occurs, which generates a lot of energy (from a little bit of mass, through the famous E = mc^2 equation), meaning that stars continuously emit energy that didn't exist yet as energy previously. 217.102.196.190 (talk) 07:10, 8 August 2018 (UTC)

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Idiotic conclusion cited from a supposedly-reputable reference

From this reference D'Inverno, Ray. Introducing Einstein's Relativity, Oxford, 1992 we have this idiotic statement: "In general relativity theory, it is still possible for the paradox to hold in a finite universe:[7] though the sky would not be infinitely bright, every point in the sky would still be like the surface of a star."

Why is it idiotic? Basic astrophysics: If all the sky were to become bright like a star, then stars would not be able to maintain stability in their long battles between outward photon pressure and gravitational collapse. As the Universe gradually grew brighter, stars' outer layers would heat up, they would expand to very low density, fusion would stop. All the stars would die, smaller ones losing stability at lower external light intensity. (And of course, we would not be around to observe or comment.) QED. YodaWhat (talk) 14:30, 21 July 2019 (UTC)

1) the page isn't referenced, 2) do you have a RS that supports your statement? Your personal observations are less than useless on Wiki.

Fractal geometry solves Olbers paradox

Olbers' paradox is most easily solved and explained using the fractal geometry of https://en.m.wikipedia.org/wiki/Benoit_Mandelbrot

see https://en.m.wikipedia.org/wiki/Fractal

Michael Hubertz (talk) 11:19, 14 January 2020 (UTC)

Change title?

Shouldn't the title be either Olbers' "paradox" or "Olbers' paradox". There's no paradox here at all, just an observation like any other, that needs an explanation (of which several have been provided). — Aldaron • T/C 19:27, 1 June 2020 (UTC)

Requested move 12 July 2020

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this discussion.

The result of the move request was: not moved. (closed by non-admin page mover) Calidum 04:25, 27 July 2020 (UTC)

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Olbers' paradox → Olbers's paradox – Singular possessives should end with apostrophe + "s" regardless of spelling (MOS:POSS). This undoes an undiscussed reversion of an equivalent page move. — RAVENPVFF · talk · 08:55, 12 July 2020 (UTC)

This is a contested technical request (permalink). Anthony Appleyard (talk) 15:07, 12 July 2020 (UTC)

• @Ravenpuff and Deacon Vorbis: queried move request Anthony Appleyard (talk) 15:08, 12 July 2020 (UTC)
• This is likely to be controversial. The quick sampling of sources I checked all used a terminal apostrophe without the extra s. See also Stokes' theorem, where there's been some thought that well-established spelling trumps MOS guidelines. –Deacon Vorbis (carbon • videos) 14:39, 12 July 2020 (UTC)
• Oppose per WP:COMMONNAME. —David Eppstein (talk) 16:36, 12 July 2020 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Reliable source for Cosmas Indicopleustes on this topic

The first sentence of the history section claims that Cosmas Indicopleustes was "the first one to address the problem of an infinite number of stars and the resulting heat in the Cosmos". Can we either get a better source for this than the Greek passage given in [2] or delete the claim?

Indicopleustes is famous for promoting the idea that the Earth is flat based on his interpretation of biblical passages, but I've been unable to find any reliable source concerning his position on the finiteness or otherwise of the cosmos. The article Christian Topography makes no mention of this claim. Vaughan Pratt (talk) 16:52, 23 October 2020 (UTC)