Practically everybody in the western world has heard of the big bang. If it is the correct model of creation, then it is the single most important event in the history of time, because it is the start of the history of time, and its effects can still be observed today.
The big bang occurred as near as
anyone can estimate, around 13.7 billion years ago. However it should be noted
that the Big Bang actually took place before the start of time!
(Quite a brain fryer...) The physics of this is very complicated, and as this is
a chemistry related site is not something that will be looked at in detail, but
in principle, it is the result of the breakdown of symmetry of one of four
extended space dimensions into time (which can only be traversed in one
direction), thus forming "space-time". (For as gentle an
explanation of this as you'll find, try Stephen Hawking's - "A Brief
History of Time" or, if you're braver, Brian Greene's - "The
Elegant Universe".)
Contrary to popular myth, the Big Bang was not in fact an explosion by its usual definition. In explosions energy is released (normally transferred from chemical potential) suddenly, and is "blown" outwards, expanding into its surroundings thus cooling it. Before the Big Bang all the mass and energy in the universe was concentrated into a tiny point, and the inflationary expansion of the Universe caused the expansion and cooling of the energy within it rather than the other way round. The inflationary expansion of the universe is observable as there is no center to the the explosion, and no location of the Big Bang. The cooling of the universe has been constant throughout it and it has now cooled to an almost uniform 2.728K. All the galaxies in the universe are moving a way from each other at the same rate proportional to the distance between them.
(i) Hubble's Law: V = HD where:-
V= velocity at which galaxies are moving apart
H = Hubble's Universal Expansion Rate
D = Distance between galaxies.
This inflationary model is often
shown using a balloon with dots to represent galaxies drawn on, (this is in
essence what is shown in the video clip above), and this is a useful idea.
However, space is three dimensional whereas the surface of the balloon is only
two dimensional, thus the curvature of space is hyperspherical, represented by
the spherical surface of the balloon. Many of the same principles do apply
though; if you travel long enough (and fast enough) in a given direction, you
will arrive back where you started. Photons (light and EM radiation) are
confined to the curvature of space, therefore it is possible to see
"around" it, thus we can see other galaxies, and the expanding universe.
Because they have mass (E=mc2 and l
= h / mv
- wave particle duality) photons, like all particles are affected by gravity,
this is because mass alters the curvature of space which photons are required to
follow.
Just before the Big Bang, all the Universe was concentrated into a singularity, a point of infinite density, so small that not even atoms, electrons or quarks could form. There was only energy. As it expanded and cooled, four distinct universal forces began to work; gravity, electromagnetism and the strong and weak nuclear forces. These four forces are the driving force behind all science, and the beginnings of chemistry.