14 DAY TRIAL // Probably everybody has heard that the Universe is expanding and that it has began with a "bang". In the beginning, around 12 to 14 billions years ago, the entire Universe was in a highly condensed state; nonetheless it "exploded" and it expanded up to its current dimensions. And supposedly it is still growing. Cosmologists wonder whether this expansion will last forever or it will eventually stop and everything will start collapsing due to gravitation.
However, for half a century, an increasing amount of evidence has mounted showing that the very idea of an expanding universe might be wrong after all. The evidences originally thought to support the idea of an expanding universe prove to be less clear cut. All these mounting doubts have led this year to the "First Crisis in Cosmology" conference in Portugal.
There are two main reasons for believing the universe is expanding:
The red shift argument
In order to understand this argument one has to know what light is and how it is emitted. Light can be understood in two different ways: either as a wave or as a beam of particles. In the wave picture a ray of light is a superposition of waves each wave having a certain wave-length. In the particle picture a ray of light is a beam of particles (photons) each particle having a certain internal energy. The color of a ray of light is related to the wave length or, equivalently, to the energy of photons. One can easily see what is a ray of light made of with the help of a prism. For example, when white solar light passes from a prism one gets a rainbow on the other side.
When an atom emits light (for example when a gas is heated it emits light - think about fire which is heated air) it does not emit all the wave-lengths or, in other terms, it doesn't emit photons having any energy. It emits only certain wave-lengths or only photons having certain particular energies. In other words, each atom has a certain optical "fingerprint". If one takes a certain ray of light and passes it through a prism one can tell what atom emitted that light or what ensemble of different atoms emitted that light. When one looks in such a way to the light coming from far away galaxies, one discovers the exact same optical fingerprints - therefore one can deduce that the entire Universe is made of the exact same kind of atoms. However, these optical fingerprints are shifted. They are either red-shifted (i.e. shifted towards lower energies), or blue-shifted (i.e. shifted towards higher energies). This shift can be understood as being caused by the fact that the galaxies move: the galaxies moving away from us are red-shifted, the ones moving towards us are blue-shifted.
When Hubble observed a large number of galaxies he was surprised to see that the majority of galaxies are red-shifted. Therefore, it was deduced that most of galaxies move away from us. This meant that the entire Universe seems to expand.
The cosmic background radiation argument
When George Gamov argued in favor of the idea that the Universe had a beginning, and that it started from a highly condensed state, he predicted there should be some background radiation leftover from the moment of Big-Bang. This radiation had to have a very low temperature and to be isotropic (i.e. it does not come from a certain direction; it is as if it comes from all directions). Some years later, such a radiation was indeed discovered. Or so it was thought...
What provoked the crisis?
First of all, the red-shift argument assumes that the Universe is empty, it assumes there is virtually nothing between the galaxies. However, this assumption proved to be false. When Grote Reber, the inventor of the radio telescope, decided to see how does the night sky look through a hectometer radio telescope he was surprised to find that such low-energy light does not appear to come from stars (like usual visible light). Instead of being emitted by stars, such light appears to be emitted by the intergalactic void! So, this "void" isn't so void after all. Using plasma theory, Reber managed to compute, given the observed intensity of the low-energy light, how much matter was there in the intergalactic "void". The result? Well, 99% of all the matter in the Universe seems to be there in its most primitive form of electrons and protons!
This has serious consequences, one of them being that the visible light coming from stars doesn't cross empty space in order to reach us, it passes a plasma of electrons and protons. One of the things that happen when light encounters electrons is that it scatters on them. The Compton Effect is an inelastic form of scattering: light scatters on electrons and looses some of its energy in the process. So, light coming from far away galaxies passing through the intergalactic plasma of electrons and protons must lose energy by means of Compton Effect. So, there is a red-shift due to Compton Effect. Moreover, it can be computed that this effect leads to the exact same result as the assumption that the red-shift is due to Universe expansion.
Secondly, some light scatters on electrons again and again and again, thus losing almost all its energy. This can be a different explanation of the cosmic background radiation. However, this explanation does not account for the fact that the background radiation seems to be isotropic. According to this explanation, the background radiation should come more or less from certain direction.
Well, new evidence appeared when NASA launched the Wilkinson Microwave Anisotropy Probe for the purpose of mapping the background radiation more precisely. When cosmologists began to decipher the received data, "bizarre" things struck them, such as the fact that the background radiation isn't isotropic after all, but it appears to come from the direction of the Virgo supercluster!
These are some of the maybe most important ingredients of the current crisis in cosmology. Although the jury is still out and it remains to be seen whether the Big Bang theory is indeed wrong, serious doubts now exist. Now it seems to be again possible to imagine the endless, boundless, stable Universe Grote Reber argued for 30 years ago: "There is no beginning nor ending. The material universe extends beyond the greatest distances we can observe optically or by radio means. It is boundless. The energy from hot material is recycled by electrodynamic (not thermodynamic) means. The material from dying galaxies is recycled into new galaxies. Details of material and energy distribution change on a small scale. Over any large volume and long time the gross features of the universe remain stable."
