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Origins of the universe theories?

by Clover228
Tags: origins, theories, universe
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Clover228
#1
Apr11-09, 07:03 PM
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Hi everyone.. I'm supposed to find the pros and cons of major and minor theories on how the universe began.

The only things i have so far are the big bang and creationisme..but i cant think of anything else! Help ! =(
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nicksauce
#2
Apr11-09, 07:47 PM
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Well creationism isn't a theory, in the scientific sense of the word, so you can throw that out right now. Pretty much all scientists now believe that the universe began with the big bang 13.7 billion years ago, and there are not really any mainstream competing theories, as far as I know, that could overturn this notion. There are different ideas about the big bang, such as inflation, but they all include the big bang. There is, however, lots of research being done these days regarding what, if anything, happened before the big bang; this field is known as Quantum Cosmology.

Also maybe explain what you mean by pros and cons. To me that suggests some sort of social implication, but maybe you mean the strengths and weaknesses?

Edit: However, if you actually do want to write about why creationism is wrong, and the evidence supports the big bang model, we can certainly help you out. If you aren't familiar with the evidence for the big bang model, I would suggest listening to the podcast "Astronomy Cast", specifically episodes five and six titled "The Big Bang and the Cosmic Microwave Background" and "More evidence for the Big Bang" ,respectively. http://www.astronomycast.com/archive/
marcus
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Apr11-09, 09:13 PM
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Quote Quote by Clover228 View Post
Hi everyone.. I'm supposed to find the pros and cons of major and minor theories on how the universe began.

The only things i have so far are the big bang and creationisme..but i cant think of anything else! Help ! =(
Clover if it is a homework assignment or term paper, or other school-related work, then we have a special section
http://physicsforums.com/forumdisplay.php?f=152

We are not supposed to give very much help with school coursework here at this Cosmology forum.

In my signature at the end of the post, in small print, are some links.
The astro.princeton.edu
and the einstein-online links may be relevant.

Bounce cosmology is attracting a lot of research interest these days. Here are some papers that are mostly on it:
http://www.slac.stanford.edu/spires/...tecount%28d%29

You can see papers here written 2006 or later which have been cited over 100 times. This is usually a sign of much research interest.
In this version of the big bang the conditions are created by the collapse of a previous spacetime region. In the quantized gravity of Loop Cosmology quantum effects make gravity repel at very high densities, so the collapse can lead to a rebound ("big bounce") and then to an expansion.
Most of the first 20 or 30 papers that the Spires search turns up will be about the bounce cosmic model.

Roger Penrose has an alternative to the bounce model. Google "Penrose Cambridge" to get his 2005 talk about his idea.
Like many of the other models being studied, it goes back in time before the big bang.

The idea that "time begins" at the big bang seems to have gone out of fashion with the people who are actually doing the research, so there are a number of pre-big bang concepts about conditions that could have led up to the big bang. It is seen as the beginning of the current expansion but not necessarily as the beginning of time.

As it says at Einstein-Online, in the essay called "A Tale of Two Big Bangs" most cosmologists would be surprised if it actually turned out that there had been a singularity. They talk about the putative singularity as a way to mark a moment in time, but it is just a convenient time-marker---the place where the classical 1915 General Relativity theory breaks down. (This does not mean that Nature breaks down! )


BTW a new book on pre-big-bang ideas will be coming out in October. Too late to help with your school work. I do not recommend the book, but it is probably good to know of its existence. Here is the table of contents:
http://www.springer.com/astronomy/ge...etailsPage=toc
Here is a general description:
http://www.springer.com/astronomy/ge...-3-540-71422-4
==quote==
...
...
Written by the leading protagonists
...
The Big Bang model is now both theoretically and empirically well established. However, the very beginning of our universe still remains mysterious. General Relativity breaks down at very small spatio-temporal scales and at high energy densities. That is why Quantum Cosmology is needed. Recent developments open up the exciting new prospect of going "beyond" the Big Bang and even finding a physical explanation for it. Surprisingly, the ancient idea of a past-eternal universe is being revived, and fascinating new approaches are also being developed. This book provides an up-to-date overview of the competing scenarios in cosmology and discusses their foundations, implications, and philosophical aspects. It gathers original contributions from the world's leading researchers in Quantum Cosmology, who describe their own work and results in a manner understandable even to non-specialists.
==endquote==

atyy
#4
Apr11-09, 10:35 PM
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Origins of the universe theories?

Aninos, http://relativity.livingreviews.org/...es/lrr-2001-2/

Section 2.2 "The isotropic and homogeneous FLRW cosmological model has been so successful in describing the observable Universe that it is commonly referred to as the “standard model”. Furthermore, and to its credit, the model is relatively simple so that it allows for calculations and predictions to be made of the very early Universe, including primordial nucleosynthesis at 10-2 seconds after the Big Bang, and even particle interactions approaching the Planck scale at 10- 43 s . At present, observational support for the standard model includes: .......... In an affort to address these questions, it should be noted that many other cosmological models can be constructed with a late time behavior similar enough to the standard model that it is difficult to exclude them with absolute certainty. ........."
yogi
#5
Apr12-09, 01:01 AM
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I personally have always had a great interest in de Sitter's exponentially expanding universe - it has no beginning in the temporal sense; it behaves like so many physical things we already know to obey the interesting mathematics of natural logs - and what could be a better example of a physical system than the universe itself. In its original form, it was empty of matter, but it doesn't have to be if one incorporates the idea of accelerating expansion and self creating matter. In fact you can get a variety of different universe(s) from the de Sitter and anti de Sitter space forms depending upon where you take slices. Harrison has a number of examples of different universes in his book "Cosmology" You might also look up the ideas proposed by Milne and McCrea.
Chronos
#6
Apr12-09, 03:18 AM
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An interesting question is what fundamental properties dominated the universe at the moment of the BB? What values did they have, and why? These are the questions modern scientists ponder.


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