Science Forums 2

[CraigD]

Originally Posted by Little Bang

I must make the assumption that gravity did not exist for the next several months or even years since the entire mass of the universe is contained within this expanding sphere one would think that like a black hole nothing could escape.

Originally Posted by Little Bang

After the first second the universe should be a sphere with a diameter of two light seconds that contains all the matter of our present universe. Then according to wiki gravity should now exist. If that is true why wouldn't the enormous gravitational well prevent any further expansion?

It’s a significant misunderstanding of the theory to assume that the Big Bang Theory describes the universe gradually expanded for several months after the Big Bang, or that it’s diameter was 2 light seconds 2 seconds after the big bang.

According to the theory, the universe expanded to a few orders of magnitude (roughtly a factor of 1000 of its present size, about lightyears) or its present diameter between and seconds after the Big Bang, a period known as the inflationary epoch, a “long time” (about 1 second) before the lepton epoch.

It should be noted that, like all of the very early universe described by the Big Bang theory, the detailed mechanics of the inflationary epoch are described only by very speculative theories and experimental evidence. Best present-day theory is very good at predicting and experimentally testing the behavior of chemical elements and high-speed particle collisions, but much less at detailed descriptions of the very early universe as described by the Big Bang theory. Directly experimentally testing theory in this domain – that is, recreating conditions similar to the described early universe – is very difficult, the realm of giant, very expensive particle colliders, whereas indirect confirmation of its predictions, which have been very successful and instrumental in creating and refining features of the Big Bang theory, particularly cosmic inflation are in the realm of astronomy.

Originally Posted by Pluto

If matter cannot be create or distroyed than we can assume that the matter existed in some form of compact degenerate matter throughout the universe in various points until the TIME came to eject this matter forming the so called Big Bang throughout the universe at the same time.

That matter cannot be created or destroyed is not an assumption of the Big Bang theory or modern physics in general.

That “matter” – more precisely hadrons and leptons such as protons, neutrons, and electrons – can be destroyed, producing energy – typically in the form of photons – is well predicted by theory and confirmed by experiment. More, that mass/energy can appear “from nothing” is a key prediction of quantum mechanics, and one of the leading candidates to answer the question “what was the Big Bang?” This proposed mechanism, quantum fluctuation, is experimentally shown to exist as a very small effect. In using it as an explanation for the Big Bang, proponent suggesting that it can, with very low probability, be a very, very large one.

For the probability of such a very low probability event occurring to become likely, a long time is needed. Edward Tryon summarized this in the famous (at least among cosmology enthusiasts) quote "Our Universe is simply one of those things that happens from time to time". We’ve discussed this a few times at hypography: searching the forums for “Tryon” will find these discussions.