The big bang was not an explosion, and the singularity is not a point in spacetime. The big bang is a mathematical property of a class of solutions of Einstein's equation, which describes the relationship between how things are distributed in the universe and how those things move. The original big bang theory is the claim that the universe is described by one of those solutions. Since then, other big bang theories have been developed. Some of them have even disposed of the initial singularity and describe the big bang as a phase transition that occurred after an initial period of rapid inflation.filegraphy said:What I was thinking is that we know if the Big Bang occurred that it explains why we think the universe is expanding. I thought about what force triggered the singularity to expand into space itself. Using Newtons First Law of Motion, that a body remains at rest or travels in a straight line unless acted on by another force. Can somebody explain what force acted upon our universe, 13.7 billion years ago?
Fredrik said:I suggest that you follow diogenesNY's instructions here on how to get free access to a good article about the big bang.
(The article I mentioned is the same one that diogenesNY is talking about. If you follow his instructions, you can read it for free).Fredrik said:The big bang was not an explosion somewhere in space. I know that's what the name suggests, but it's more wrong than thinking that there's buffalo meat in Buffalo wings. These two posts might make things a little bit clearer: 1, 2. The http://www.scientificamerican.com/article.cfm?id=misconceptions-about-the-2005-03 that was mentioned earlier in this thread is even better, but it looks like you will have to pay for it.
Stephen Hawking's quantum cosmology uses "imaginary time" as more fundamental than "real time". The principle of causality only makes sense in real time where there are light cones at each spacetime point event. It is violated in imaginary time. The missing mass enigma may be a clue that real time is only the top of an iceberg. Most of the universe may still exist in imaginary time. Mathematically spacetime is described by a metric tensor which has a topological property called the "signature". The light cone only exists in real time where the signature is -+++. There is no light cone in imaginary time where the signature is ++++. The phase transition from imaginary to real time which starts the Big Bang is a topological transition. Is it controllable from the far future of real time in a self-consistent loop?
TimBowe said:Thus, the big bang can be seen as the beginning of bubble nucleation, and the spontaneous nucleation of universes.
That is unknown and probably unknowable. It is conceivable the big bang created time, hence, the age of our universe is indeterminate.nickdk said:Completely curious. Would this suggest that essentially our universe is spawned from other universes? Or say, our universe was born from the energy&mass of another...and it then adjoined the others?
However, if we invoke quantum mechanics, as Hawking and James Harte have done, the Heisenberg uncertainty principle requires the light cone, instead of coming to a point, to be rounded into something like a hemispheric cap. The radius of the cap is the Planck length, which is very small, about 4 X 10~33 centimeters. This cap forms during the Planck time from the beginning of the universe, which is about 10-43 seconds. While very small, this radius is still infinite compared to a point singularity, and its existence would drastically change our ideas about the origin of the universe.
Above the point where the hemispheric cap joins the cone, time runs forward in the usual way, but below it, for earlier times, time gradually turns into space and as we get finally to the bottom of the cap, it disappears altogether. The situation is similar to being at the South Pole and asking which direction would take a person directly toward the North Pole. The answer is that there is no such direction, since all directions at the South Pole are perpendicular to the north-south axis of Earth, which corresponds to time in this analogy.
When exactly at the South Pole, all paths taken eventually lead us northward, but none initially goes in the direction of the north-south axis.
Nobody knows. All we know is that it is expanding. General relativity, when applied to the smooth radiation-dominated early universe, tells us that the universe is either expanding or contracting. We happen to exist in an expanding universe, and so theoretically, the expansion is imposed as a boundary condition.filegraphy said:I was just wondering what acted upon the beginning of our universe to cause it to expand?
The Big Bang theory is the widely accepted scientific explanation for the origin and evolution of the universe. It suggests that the universe began as a single point of infinite density and temperature, and has been expanding and cooling ever since.
The exact cause of the Big Bang is still a subject of debate among scientists. Some theories suggest that it was triggered by a quantum fluctuation, while others propose that it was a result of the collapse of a previous universe. However, the precise cause is still unknown.
Dark energy is a mysterious force that is thought to be responsible for the accelerated expansion of the universe. It is believed to make up about 68% of the total energy in the universe and counteracts the gravitational pull of matter, causing the expansion of the universe to accelerate.
Scientists have observed the expansion of the universe through various methods, such as measuring the redshift of distant galaxies and the cosmic microwave background radiation. The redshift of light from galaxies indicates that they are moving away from us, while the cosmic microwave background radiation is the leftover radiation from the Big Bang and provides evidence for the initial expansion of the universe.
Based on current observations and theories, it is believed that the universe will continue to expand indefinitely. However, the rate of expansion may change over time due to the effects of dark energy and the gravitational pull of matter. It is still a subject of ongoing research and debate among scientists.