Part 4 (chapters 4-1 –› 4-4) presents an infinite universe as an alternative for big bang cosmology.

If there is a lot of dark matter in the universe and if the universe has a certain equilibrium temperature then dark matter objects in galactic and, especially, intergalactic space may cool down to that equilibrium temperature and thus dark matter may be the main component that acts as the intermediate that sends out the photons of that equilibrium temperature, which may be the cosmic background radiation (CBR, where I write cosmic background radiation I mean the cosmic microwave background radiation). Thus energy may be transferred from high energy photons to low energy photons.
Dark matter may be heated up by infrared light, visible light, ultraviolet, X-rays and other radiation exceeding 2.73 K and it may be cooled down by (longer than 2.73 K) waves of the cosmic background radiation and other waves with temperatures less than 2.73 K.
[July 2004: Pulsars (6-1) and radio loud activity (5-2) may harbour cooling down mechanisms in the Universe. The Boomerang Nebula in the Milky Way has a temperature of 1 Kelvin (6-1). End July 2004]

The cosmic background radiation spectrum in the wavelength interval 2.5 mm - 0.5 mm is a perfect black body with a radiation temperature of 2.73 K. The extremely smooth curve may be caused by very much dark matter cooled down to a precisely set equilibrium temperature.

Dark matter like planets or old cooled down stars may turn into blackbody radiators.
But if we look at our Solar System and especially at the asteroid belt, the Kuiper belt and the van Oort cloud: small pieces of debris may have a big total surface and may play a big(ger) part in setting the equilibrium temperature in the universe than the larger dark matter objects.

But dust is even much smaller and may play an even big(ger) part than the debris. [May 2004: Dust grains can shine “stolen” starlight back out at a low temperature very effectively⁹⁷. End May 2004]
[August 2004: Astronomers have discovered large amounts of ultra-cold cosmic dust in the Virgo Cluster. Up to 50 percent of stellar light in the galaxies of the cluster is transformed into infrared light by the cold dust²³⁷. The dust surrounding the galaxies has a temperature of 10 K. Perhaps that dust further away from galaxies can have a temperature of 2.7 K. End August 2004]
Or: hydrogen atoms (or free electrons as suggested by Grote Reber¹⁶) may play a role in transferring energy from high frequency radiation to low frequency radiation.

And: perhaps gravity particles may be the intermediate through which the equilibrium temperature of the universe settles down itself. If the redshift of far away galaxies is caused by gravity/ether particles (1-2) then: while a light wave is cooled down by gravity/ether particles the gravity/ether particles are being heated by the light wave. The heated gravity/ether particles in their turn may give energy to cooler light waves. Thus gravity/ether particles may act as energy transducer (too).
[May 2003: The late Dr. Toivo Jaakkola has suggested this too (see Jaakkola posthumously in Pushing Gravity⁵). End May 2003]
[January 19 2007: And: when gravity particles get more energy because of tired light redshift the energy of the gravity particles is put into gravitational energy by pushing for example the mass of the Earth together or by pushing the stars of a galaxy together, see also Edwards⁴⁴⁸. End January 19 2007]

Of course all mentioned energy transducers may have their part in settling down the equilibrium temperature of the Universe (i.e. the CBR), they don't have to exclude each other.

[November 2003: Also the physics professors Assis² and Marmet¹¹ as well as many others see the cosmic background radiation as the equilibrium temperature of the Universe. End November 2003]

Radiation of a certain wavelength may pass energy to radiation with a cooler wavelength with dark matter, dust, hydrogen, electrons, gravity particles or some other substance as the intermediate. Perhaps there is even a possibility that photons of high energy can give energy to photons of low energy directly.

[May 2004: When the CBR is caused by dark matter in, for instance the halo of our Milky Way then the solution of the dark-sky-at-night problem is not solved by the CBR. The dark-sky-at-night problem then may be solved by a combination of reasons: dark matter absorbing visible starlight, photons turning back into baryonic matter and tired light redshift (4-2). End May 2004]

[June 2004: When CBR indeed does not come from very far away objects then another wavelength may be the answer that brings us a not/never-dark-sky in a certain way. A study by big bang astronomers confirmed that the hard X-ray background is mainly due to Active Galactic Nuclei (AGNs). Observations revealed that a large fraction of them are of comparatively low brightness (referred to as low-luminosity AGNs), heavily enshrouded by dust and located at distances of 8,000 - 9,000 million (big bang) light-years (corresponding to a redshift of about 1)¹⁸⁰. (A redshift z=1 may rather stand for a distance of about 20 billion light years, 5-3.) [September 1 2005: Recent observations seem to confirm that the glowing X-ray sky is caused by AGNs³⁴⁶. End September 1 2005] [March 15 2006: Lately astronomers observed that the diffuse glow of background X-ray radiation isn't really a background glow, but rather the X-ray radiation from hundreds of millions of AGNs⁴⁰⁴. However, if the Universe is infinite there may still be a dilute X-ray background glow by much more AGNs that are further away but which are too faint to be spotted (so far) by the researchers as single AGNs. End March 15 2006]
Thus, the dark-sky(-at-night) riddle in a way comes up again when thinking about this hard X-ray background: everywhere you look in the sky you measure/see hard X-rays. When far away quasars outshine their host galaxies (5-3) then it may be that hard X-rays (i.e. AGNs) indeed bring (X-ray) light from every corner of the Universe and thus bring us a not-dark-sky because somewhere there always is a (very far away a “naked” AGN, i.e. AGN outshining its host galaxy) to be found. (There may also be a gamma-ray background because of distant “blazar”, which seem to dominate the gamma-ray sky¹⁹⁴, 5-3, gamma ray-loud “blazars”, may be a major source for the Cosmic Diffuse Background above 100 MeV¹⁹⁵.) End June 2004]
[August 2004: Scientists at Columbia University and Barnard College have found that the majority of the gamma rays outside of our galaxy are likely emitted by galaxy clusters and other massive structures. The sheer mass of a cluster serves as a gravitational drain, drawing in matter at speeds of up to a thousand miles per second. Electrons in this flow are accelerated, with an additional boost from magnetic fields, to near light speed and collide with microwave light of the cosmic microwave background. These microwave light particles, or photons, are bumped up to the gamma-ray photon energy level. The gamma rays form a halo around the galaxy clusters²³⁴. This may explain the Universe's gamma-ray background too. End August 2004]
[September 2 2005: Quasars outshine everything else in the universe in X-rays. By counting the background buzz of X-rays, it is possible to predict the approximate total number of quasars. But this estimate has not matched previous X-ray and visible-light observations of actual quasars, which number far fewer than expected by big bang astronomers³⁴⁷.
In an infinite universe there are much more AGNs that can account for the glowing X-ray sky. End September 2 2005]

The dark matter in our halo may be 2 x 10¹¹ solar masses⁸. If this dark matter would be around in only Earth-dark-mass-magnitudes then there would be 2 x 10¹¹ x MSun / MEarth = 3.3 x 10¹⁶ dark “earths” in the halo behaving as a black body radiator and turning all kind of radiation in CBR radiation.

(The quantities of dark matter that are supposed to be in our Galaxy or in superclusters of galaxies is calculated by the virial theorem, which states that galaxies and superclusters do not expand nor contract, which is, I think, not the case, I think they shrink (4-1, 4-3). So corrections may have to be made, which eventually may lead to different outcomes of dark matter quantities.)

[May 2003: As mentioned in 4-1: Newton's law of universal gravitation may have to be modified, so there may be no (or less) necessity for dark matter in our halo anymore.

Many dissidents, like Assis², Ghosh³ and Hatch⁴ think that there is a “preferred frame of reference” (some kind of “average position” of all the mass in the universe) which they link to the cosmic microwave background radiation.

This may be very true indeed, but it may also become the next paradigm that holds up scientific progress. If it turns out that there is always a bigger supercluster to be found (4-1) then there may be no such thing as “preferred frame of reference” and then gravity particles can't be linked to all the mass in the universe and have to be linked to a smaller amount of mass of the universe.
This “smaller amount” may be much bigger than the universe as we know it right now, i.e. than the Hubble Space Telescope can see right now.
The reach (or: the magnitude of “our local frame of reference”) of gravity/ether may be connected with the speed of gravity/ether particles/waves (3-1).

Especially the 10^-4 K temperature dipole difference in the CBR brings a general agreement among dissidents about this preferred reverence frame linked with CBR. (Perhaps the dipole difference can also be caused by shrinking of our Galaxy, 4-1, 4-3).
This dipole difference can be seen as speed + direction of our Local Group relative to the CBR⁸ (5-4).
The dipole difference seems to be consistent with the bulk motion of the Local Group falling into the Great Attractor⁸. This may mean that the CBR is linked with the matter connected to the region defined by the Great Attractor (which I call our Great Chappell, 5-4). End May 2003]

[April 27 2005: The accuracy of the big bang formulas with respect to the cosmic microwave background radiation seems to be thin thread by which the big bang model is still hanging. However, many models wil be able to describe the cosmic background radiation with accuracy. The accurate description of the cosmic background radiation is not the miracle of the big bang model, but the miracle of the very smooth curve of the cosmic background radiation, which is able to make mathematical models shine brightly because of its smoothness. End April 27 2005]

[September 1 2005: A new analysis of cool spots in the cosmic microwave background may cast new doubts on a key piece of evidence supporting the big bang theory of how the universe was formed. Two scientists at the University of Alabama in Huntsville looked for but couldn't find evidence of gravitational lensing where you might expect to find it, in the most distant light source in the universe, the cosmic microwave background. If the cool spots are too uniform to have traveled to Earth from near the beginning of time, cosmologists are left with several alternative explanations, the astronomers say. The most contentious possibility is that the background radiation itself isn't a remnant of the big bang but was created by a different process, a ‘local’ process so close to Earth that the radiation wouldn't go near any gravitational lenses before reaching our telescopes³⁴⁵.
Although widely accepted by astrophysicists and cosmologists as the best theory for the creation of the universe, the big bang model has come under increasingly vocal criticism from scientists concerned about inconsistencies between the theory and astronomical observations, or by concepts that have been used to ‘fix’ the theory so it agrees with those observations. These fixes include theories which say the nascent universe expanded at speeds faster than the speed of light for an unknown period of time after the big bang; dark matter, which was used to explain how galaxies and clusters of galaxies keep from flying apart even though there seems to be too little matter to provide the gravity needed to hold them together; and dark energy, an unseen, unmeasured and unexplained force that is apparently causing the universe not only to expand, but to accelerate as it goes³⁴⁵.
I agree with everything but the doubt about dark matter. If we live in an infinite universe there must be very much darkened stars, which then may account for dark matter. End September 1 2005]

But Sahu and co-workers measured, beside the large changes in light magnitude, also very many very small deviations that were a little larger than the photometric error, which they did not explain in the article³⁷. These small deviations may be due to many small dark matter masses (for example with mass-magnitude of our Moon or smaller) that pass in front of the observed object, thus causing small microlensing effects.

[May 2004: In 2001 also another microlensing event was reported¹¹⁰. This microlensing event was one of the very first seen in an external galaxy. It was situated far from the centre of the Andromeda galaxy, outside the stellar bulge. It had a very short duration, under two days. The interpretation of the event raised 2 possibilities according to the team of astronomers. First, the dark object could be a brown dwarf in the outer parts of the Milky Way Galaxy or in the Andromeda Galaxy. The other possibility is that the dark object could be a low mass star in the disk of the Andromeda galaxy. End May 2004]

The dark sky riddle may be explained by dark matter radiating its mass and energy away in the form of cosmic microwave background radiation (4-2).
Astronomers, under whom Fournier d'Albe in 1907, early in the twentieth century already suspected that starlight is absorbed by dark matter drifting in space between the stars⁶. (Harrison⁶ also reports that already in 1744 Jean-Philippe Loys de Chéseaux attributed the darkness of the night sky to interstellar absorption.)
[December 2003: In 1823 also Heinrich Olbers argued that the missing starlight may be absorbed by interstellar(/intergalactic) matter, but in 1848 John Herschel argued that absorbing matter heats up and soon emits as much radiation as it absorbs⁶ and today's conventional scientists see this as the final answer where it concerns absorption by interstellar matter. But in an infinite universe there must be a mechanism that turns (the energy of) radiation back into baryonic matter and this mechanism may be the reason why there is an equilibrium temperature. One such mechanism may be: pulsars absorbing low temperature radiation (like CBR) (6-1). Another mechanism may be: gravity/ether particles cooling down radiation (4-2) combined with a mechanism that turns gravity/ether particles into baryonic matter (3-2); in a way this mechanism was proposed by McMillan and Bondi, see hereafter. End December 2003]
[February 2004: Fusing light elements gives energy, mostly in the form of photons. Above iron this changes, then fusion takes energy, perhaps mostly in the form of photons (but perhaps also in the form of gravity particles being absorbed). This may be the cooling down mechanism of the universe next to fusion of light elements (i.e. stars burning) heating up the universe. End February 2004]
[July 2004: In 5-2 I reason that radio loud activity by AGNs may be caused by elements breaking down into (mainly) HII and electrons. Elements like iron and lower elements breaking down into HII and electrons then is a cooling down mechanism too. End July 2004]

Another way of explaining the dark sky at night riddle is: radiation may be transformed back into hydrogen somehow (4-1).
Radiation turning back into hydrogen, thus solving the dark sky riddle, already was proposed by McMillan in 1922⁶.

Another solution of the dark sky at night riddle may be: tired light redshift gradually changing visible light into CBR (4-1). [May 2004: Though tired light may be part of the solution to the dark sky at night riddle indeed, tired light may not be likely to explain the CBR, for professor Wright argues that starlight can not turn into CBR⁹⁴. End May 2004]
Bondi already proposed in 1955 that the dark sky riddle might be solved by redshift⁶.

In the early twentieth century Carl Charlier in Sweden received wide publicity by adopting Kant's idea (4-1) of a hierarchy of clusters of increasing size. Clusters of progressively larger size have progressively lower average density, and the lookout limit therefore progressively increases. By arranging that the density of the clusters decreases sufficiently rapidly with increasing size, the lookout limit can be made indefinitely large. In this way the sky at night becomes dark⁶.

[October 16 2006: A new view from the Hubble Space Telescope made in the Hubble Ultra Deep Field shows objects “all over the place”⁴³⁸. So perhaps the sky at night may not be so dark after all in an infinite universe. End October 16 2006]