The big bang theory (or Big Bang theory) is the popular name for the collection of hypotheses, models, and theories which are the current, best, scientific cosmological explanations. The name ‘big bang’ was first used by Fred Hoyle, way back in 1949, in a BBC radio program; he meant it sarcastically, but it stuck!
Perhaps the most widespread popular misconception of the big bang theory is that it describes how the entire universe was created ‘from nothing’; almost as widespread is the misconception that in the big bang theory the universe began from a singularity. In fact, the concordance cosmological model (THE big bang theory) is silent on the origin of the universe, because this highly successful model is nothing more than the application of the two most successful theories in physics, period, to the universe as a whole.
And what are those two theories? Einstein’s theory of general relativity (GR), and the Standard Model of particle physics (which is based on quantum theory). And why the big bang theory is silent on origins is because these two theories are mutually incompatible in extremely dense, energetic conditions (the ‘Planck regime’).
If the universe is isotropic and homogeneous at large scales, then it is either expanding or contracting … if GR rules. Nearly a century ago, Vesto Silpher and Edwin Hubble discovered that the universe does seem to be expanding (the further away an object is, the greater its redshift), and a key prediction of the newly published GR got a huge boost.
If the universe is expanding, then a long time ago it must have been much denser, and hotter, and lots of nuclear reactions must have taken place. When they stopped – because the universe was too cool – what was left must have been a certain mixture of hydrogen, deuterium, helium, and lithium-7. These big bang nucleosynthesis predictions, made in the 1940s, have since been confirmed.
And so on, through the prediction, and observation of, the cosmic microwave background, baryon acoustic oscillations, etc, etc, etc.
NASA’s WMAP mission webpage, Big Bang Cosmology, and its What is the big bang theory? one give good introductions to the big bang theory. For a more detailed introduction, check out Ned Wright’s Cosmology Tutorial.
Universe Today has many, many stories and articles relevant to the big bang theory; here is a small sample for your enjoyment: Explaining Dark Matter and Contradicting the Big Bang, Cannibalistic Stars May Hold Clues to the Big Bang, and 13.73 Billion Years – The Most Precise Measurement of the Age of the Universe Yet.
Astronomy Cast episodes relevant to the big bang theory include Large Scale Structure of the Universe, Homogeneity, Inflation, and The Big Bang and Cosmic Microwave Background.
Comments on this entry are closed.