BBC Focus Magazine

[M Paul Lloyd]

A very Brief History of Time.

For anyone vaguely interested this is a brief run down of how big bang theory is strung together, it’s not meant to be a definitive thesis but more a sort compressed and abridged timeline. After all how many of you have managed to read right through Steven Hawkin’s A Brief History of Time, let alone all the other stuff????
So, if you want a simplified version of a very complex subject read on, and please, any comments good or bad are most welcome.

1. In the beginning……. at least according to big bang theory, we have something called ‘Planck time’, or more precisely 10-43 (that's ten to the power of minus 43 in case you were wondering) seconds after time zero, the point at which the big bang hasn’t actually happened yet. Subsequent to this ‘Planck time’ gravity is said to be a ‘background’ effect within which ‘particles and fields evolve in line with quantum mechanics’, now does anyone truly understand quantum mechanics? Apparently if you think you do, you don’t! On closer examination this is actually a convenient let out clause that allows the big bang to occur in the first place. Yes gravity is there but it doesn’t count for some reason, clever that, otherwise it would all fall apart right now wouldn’t it?

2. So the big bang has begun and we now have an isotropic (having the same properties in all directions, essentially uniform) and generally homogeneous (much the same as isotropic really) area of space existing at around 10-36 metres in area and the temperature is a staggering 10-32 Kelvin (io followed by 32 zeros.

3. Then……………… inflation begins.
If you are wondering, inflation is not a ‘real’ observable phenomena but something that had to be invented in the 1970’s to solve two key problems in cosmology, specifically those appertaining to big bang theory.
First the horizon problem, which states that everywhere we look the universe appears the same and there is uniformity of the background radiation.
Secondly, that there simply has not been enough time since the big bang for light to have travelled across the entire universe and back.
But what the heck, this is science and apparently we can do what we like with it.
[According to Linde's chaotic model inflation starts at the Planck time, which could start as the temperature drops to a point where the symmetry of a Grand Unified Theory (a grand unified theory is still theoretical remember) is broken. This is said to have occurred when the temperature reached 1,027 to 1,028K at 10-35 seconds after the Big Bang.]

4. And then………….. inflation ends!? Hang on, sorry? I wasn’t ready!!
The time is now just 10-33 seconds since the big bang, the temperature has cooled to around 1,028K as the vacuum energy, that is said to have driven inflation in the first place, is now converted into heat, so it sort of balances out apparently. You know conservation of energy and mass, that sort of thing?
[On vacuum energy: an underlying background energy exists in space even when devoid of matter (known as free space). The vacuum energy is deduced from the concept of virtual particles which is itself derived from the energy-time uncertainty principle. Its effects can be observed in various phenomena (such as spontaneous emission, the Casimir effect, the Van-Der Waals bonds, the Lamb shift), and it's thought to have consequences for the behavior of the Universe on cosmological scales]. So….. another theoretical quantity invented to fill a gap eh? Hmmm.) Remember vacuum energy is only theoretical no-one to date has actually isolated any of it any more than they can make cold fusion work.
Apparently the rate of expansion during inflation was so rapid that the age of the universe is still a mere 10-35 seconds and yet it is now some 90%+ of it present day size!!!! As a result of this incredibly rapid inflation the homogeneous regions originating at the Planck time are now about 1 metre across, (well they have been through a lot haven’t they?) an increase by a factor in excess of 1,035 since the Planck time, but hang on, what about ‘quantum fluctuations’ (Quantum fluctuation is the temporary appearance of energetic particles out of nothing, as allowed by the Uncertainty Principle. It is synonymous with vacuum fluctuation, so still no real explanation for this one as yet, just something out of nothing eh? ) these quantum fluctuations manifest themselves during inflation causing a harmonic resonance resulting in a random pattern of low energy areas (not sure how you get a random-pattern but hey-ho whatever) with equal power on all levels.
Note that this ‘inflation’ idea breaks all the known laws of physics!
Also just to clarify this Uncertainty Principle thing, this is Heisenberg and Bohr territory, immensely complex stuff, all very theoretical and… did I say ‘clarify’? Well that might take some doing to be honest; after all we have messed about with this stuff for long enough and gone no-where with any of it!! After all, nothing is certain in uncertainty theory.
Anyway we must now consider something called Baryogenesis which is a tiny difference said to exist between the speed of interaction between matter and anti-matter that results in us having 100,000,000 antiprotons for every 100,000,001 protons, oh! and one hell of a lot of photons too.
So as the embryonic universe boils away antiprotons and protons continue to interact, annihilating each other leaving only ordinary matter behind, although the number of photons is considerably greater than the resultant protons and neutrons. If this was not so then all the anti-matter and matter would have cancelled itself out and nothing would be left to form the universe we know today.

5. We are now at 0.0001 seconds after the big bang with a temperature of about 1,013 K and the universe continues to grow and cool until 1.0 seconds after the big bang, with the temperature dropping to 1,010 K and the matter/antimatter interaction beginning to grind to a halt as the tardy bits of anti-matter are steadily wiped out.
That old ‘homogeneous area’ size (the nice even bit mentioned earlier) is now 1,019.5 metres across, although I’m still not sure quite what this means but I now think it’s possibly something theoretical?

6. Anyway the universe continues to grow and cool until 100 seconds after the big bang and the temperature is now 109 K. Electrons and positrons annihilate one another producing more photons, whilst protons and neutrons combine to make deuterons, almost all of which combine to make helium. This results in a mass ratio of 75% Hydrogen to 25% Helium, with the Deuteron/Proton ratio at 3 to 100,000. Actually things are now starting to make some sort of sense.
There are now roughly 2,000,000,000 photons per neutron or proton, which I guess helps explain why we now have so much more light than matter in the universe?
One month after the big bang the (as yet unexplained) processes that convert the radiation field to what is called a ‘blackbody’ spectrum become slower than the expansion of the universe, so the spectrum of the Cosmic Microwave Background preserves information back to this time. In other words the Cosmic Microwave Background is said to be an echo of the events that immediately followed the big bang.
Apparently blackbody radiation refers to an object or system which absorbs all radiation incident upon it and re-radiates energy which is characteristic of this radiating system only, not dependent upon the type of radiation which is incident upon it. The radiated energy can be considered to be produced by standing wave or resonant modes of the cavity which is radiating. Um, yes ok!

7. By 56,000 years after the big bang matter density begins to equal radiation density, with the temperature now at 9,000 K, and the point at which dark matter ceases to be homogeneous and starts to collapse. Don’t forget dark matter is still a theoretical quantity! Protons and electrons combine to form neutral hydrogen and the universe finally becomes transparent, with a temperature of 3,000 K.

8. At 380,000 years after the big bang ordinary matter can now coalesce as dark matter, always supposing dark matter really exists. The Cosmic Microwave Background is (seemingly) able to survive almost unchanged from this time for billions of years until the present day, so the Cosmic Microwave Background anisotropy is said to give us a picture of how the universe appeared at this time. Personally I don’t see how they can be certain of this given the ephemeral nature of microwave radiation, but I evidently don’t understand the complexity of the subject well enough to argue against it. Ho-hum.

9. The first stars form at about 100 to 200 million years after the big bang, and this re-ionizes the entire universe which has now become transparent.
This is the absolute limit of the observable universe, the point beyond which we cannot hope to see with optical instruments and which is said to be affected by red-shift and upon which all of the foregone theory is based.
This report, which comes from the very fringes of credible modern science.
“A remarkable result of the Wilkinson Microwave Anisotropy Probe observations is that the universe was significantly re-ionized at large red-shifts. The standard explanation is that massive stars formed early and re-ionized the universe around red-shift z=17. An alternative possibility exists in which the universe was re-ionized in two steps. An early boost of re-ionization is provided by a decaying sterile neutrino, whose decay products, relativistic electrons, result in partial ionization of the smooth gas. It can be demonstrated that a neutrino with a mass of mnu ~ 200 MeV and a decay time of t ~ 4 * 1015 s can account for the electron scattering optical depth tau=0.16 measured by WMAP without violating existing astrophysical limits on the cosmic microwave and gamma ray backgrounds. Re-ionization is then completed by subsequent star formation at lower red-shifts. This scenario alleviates constraints on structure formation models with reduced small-scale power, such as those with a running or tilted scalar index, or warm dark matter models.” Talk about making it complicated!!

10. Back with the real universe and the first supernovae explode which spread carbon, nitrogen, oxygen, silicon, magnesium, iron… ok, essentially everything on the periodic table up to and including uranium, throughout the entire universe. Galaxies begin to form in clusters as clumps of dark matter, whilst stars and gas begin to merge together. No, I’m not making it up this is the real stuff, honest.

11. Finally (for us at least) the Solar System and Sun form around 4.7 billion years ago.
So the time is now 13.7 billion years after the big bang, and the temperature is just 2.725 K. The homogeneous patch (I think this is really a mathematical thing, an algorithm of some sort drawn up to show what things were like during the ‘uncertain’ period of expansion/inflation, but I still don’t get it) is now 10 ttpo 29 metres across, which is supposedly larger than observable universe…………..? No I don’t get that one either!

Ok, so we are all agreed then, the universe is a big place, yes? and not a little bit complicated into the bargain!?

Which, seemingly, is getting ever bigger and more complicated all the time, but only, that is, if you choose to embrace the concept of Hubble’s law? Which states that the red-shift in light arriving here in our solar system from distant galaxies is proportional to their observed distance. This idea was first formulated by Edwin Hubble and Milton Humason (he often gets forgotten) way back in 1929 after nearly ten years of careful and studious observation. However it was not Hubble himself who suggested the concept of the big bang but actually it was a Georges LeMaitre (1894-1966) who actually came up with the idea the the universe had expanded from a single cosmic event, which is now called the big bang. Of course it was very much in LeMaitre's interests for the universe to have begun in this way, he being a Catholic Priest and all, after all, it did fit rather nicely with the idea of god's creation. Albert Einstein looked over LeMaitre's work and although he accepted that "the mathematics were impeccable the physics were abominable". Today Einstien is seen as being hopelessly out of step and this 'cosmological event' and the red-shift is held to be the basis for the expanding space paradigm and is now often referred to as one of the key pieces of evidence in support of the Big Bang. Actually it is the single most significant piece of supporting evidence in big bang theory with just about every piece of modern cosmology hanging off it like baubles on a Christmas tree.

To break it down further the more distant an observed astronomical object is located from our point of view the greater the degree to which it will appear red shifted. That is, the wavelength of the light being emitted by distant stars has been, in effect, stretched as the source moves away, at least from our apparent point of view that is.

Taking this supposition to its ultimate conclusion would suggest that not only are the majority (although strangely not all) of the observable distant objects, in the form of Galactic groups and clusters are not only moving away from each other but that this process is actually accelerating as ever more distant objects are seen to appear to be moving away from each other more rapidly again.

This leads to the inevitable conclusion that the process of expansion must be accelerating.

M Paul Lloyd © 2006