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Why big bang?

  1. Sep 17, 2008 #1
    Hey there

    Why did the big bang happened? what made it happen? what is the cause of the big bang?

    Could be vacuum fluctuations?
    Or a collision between different branes or universes?

    Could be some sort of a creator?

    What is the most proved and most appropriate theory that talks about the cause of big bang?

  2. jcsd
  3. Sep 17, 2008 #2


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    Perhaps you need to re read our site guide lines. Anyone who attempts to address your 2nd sentence will be in violation of the guidelines.
  4. Sep 17, 2008 #3
    You are absolutely right, I am sorry. I removed my previous message. Let me rephrase what I meant to say:

    There is currently no scientific theory on what may have caused the Big Bang.

    With our current observing power we cannot obtain enough information not even for the first fractions of seconds after the Big Bang (called 'the Dark Ages' among cosmologists), so anything now attempting to address those times can only be considered as pure speculation.
  5. Sep 17, 2008 #4


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    It is probably a meaningless question. There being no time before the big bang, casuality is a bit tricky. There are lots of areas in science (especially relativity and QM) where it is meaningless to ask some obvious questions such as which event happend first or where a particle is.

    Not necessarily - we don't have direct observational evidence for the early universe but we can make experiments which lead to theories of what would happen at those energies.
    We don't have observational evidence of the flight of a cannon ball at the battle of Gettysburg but we have a theory about the path the ball followed.
  6. Sep 17, 2008 #5
    I agree that, if you define time begining with the Big Bang, then yes, there is no point in asking what happened "before" and causality does become an issue. But I find asking what the Big Bang was and how it might have happened quite a meaningful question, at least in the context of addressing the Big Bang theory itself. I think that the Big Bang only covers our ignorance of what could create an expanding Universe.

    I also agree that we can do calculations and try to see what could lead to the things we actually can see and measure. But as far as I know, with the surveys done so far and the ones planned for the next few years, we can only test some of the thousands of models on inflation, for example.

    I find this area very interesting and admire the people working on it, but I think we still have a long way to go before having an elegant explanation of how the Universe started.
  7. Sep 17, 2008 #6


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    Are you actually claiming that time does not continue back before the start of expansion?
    I'm curious, mgb_phys, what scientific basis do you think there is for a statement like that?
  8. Sep 17, 2008 #7


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    Space-time continues before expansion but it doesn't exist before the initial singularity, at least not in science!
  9. Sep 17, 2008 #8


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    I don't understand why you say that. Many reputable scientists work with quantum cosmology models which reproduce the classic FRW picture but do not suffer from an initial singularity.

    What do you mean by "science", if it excludes these people? They publish in the best peer-reviewed journals. Their work is highly cited. One was elected president of the General Relativity and Gravitation society---the main professional society relevant to cosmology---last year. Another was awarded the GRG's main prize for work in cosmology.

    Last year's GRG meeting had about 600 participants---in all kinds of cosmology-related science. They have these big international meetings every three years.
    This is observational (gravitation'l wave, neutrino, gamma, CMB....) theory (black hole, structure formation, classical cosmology, quantum cosmology...). Everything.
    And in that context the quantum cosmologists stood out prominently.

    You are saying that they are not scientists?

    You are saying that what they do is not science, simply because their models don't break down at the big bang (like classical 1915 GR does) but keep on running back in time?

    The field of cosmology has changed a lot in recent years---is it possible that you are not keeping up?

    I'm curious as to why you imply those models are not "science" which continue back before the point where the classic model breaks down. Running models like that has, in fact, become science (but if you haven't been keeping up you may not have noticed.)

    As it stands, you appear to set your own opinion up in defiance the main body of professionals, conference organizers, the editorial and peer-review boards of the main professional journals, and it looks kind of, well, odd. :wink:
  10. Sep 17, 2008 #9


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    I would say they are mathematicians.
    In maths you can invent a universe with any geometry you want, with any rules of arithmatic and make consistent statements about it. But it doesn't mean it's real.

    Probably - I'm not a comsologist

    I would say that big bang time=0 model is the orthodoxy, it might be wrong but outside a subset of quantum comologists I think it is the standard model.
    quote- Professor Carroll urged cosmologists to broaden their horizons: "We're trained to say there was no time before the Big Bang, when we should say that we don't know whether there was anything - or if there was, what it was."

    There are hints of structure in the CMB which suggests an ordered state in the early universe ( see Prof Carroll) 'before' the big bang - of course you could argue then that 'THIS' big bang wasn't the original start of time , but that just pushes back the start.
    Last edited: Sep 17, 2008
  11. Sep 30, 2008 #10
    This is one of those places where science enters the faith realm, which is why it's fun to talk about.

    Really, all the ideas and theories place a 'creator' as the initial cause. I've read some really 'fluffy' papers where the author was going with some kind of eternal grouping of energy that has always existed. Considering how 'God' is defined in most modern culture these days, atheists may be hard to come by. :P
  12. Oct 1, 2008 #11
    I would hardly consider a grouping of energy as a "creator" in the deistic sense.

    I have not read these papers, but I guess if one is trying to explain the Big Bang, it makes sense to go for some kind of energy source.
  13. Oct 1, 2008 #12


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    I would like to remind the participants here not to derive in religious debates, this is against the guidelines. Please try to make meaningful contributions, and if you are joking, use smileys :smile:
  14. Oct 1, 2008 #13


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    I guess it is a matter of different standards in different disciplines. Of course, speculative theoretical physics is somehow part of science - I guess that what mgb_phys is after, is that one shouldn't forget that all this is highly speculative - especially to experimentalists who are used to quite stronger requirements for proof. It doesn't mean it isn't science of course.

    Whether time (whatever it may mean) "continues" or not before "the start" of the expansion, whether the proposed quantum models are correct or not, whether inflation is true or not remains, from the P.o.v. of an experimentalist, still a very speculative working hypothesis, while for the theorist that works on these problems, it is "almost standard science". We're still on the level of "does the Higgs exist or not", you know :smile:

    To give you a feeling, for active string theorists, it is probably almost "standard science" that the universe is 10 or 11 dimensional :wink: while an experimentalist will consider that as almost wild speculation at this point.
  15. Oct 1, 2008 #14


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    I didn't say that - I said it is the 'standard model' that time doesn't exist before the singularity. No universe, no mass-energy, no space-time = no time!
  16. Oct 1, 2008 #15


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    There are two issues here. I would say that it is speculative to assert that time does not exist before the big bang. We don't know that.

    I personally am skeptical and reserve judgement (and I think many cosmologists do as well). Regular time evolution may continue back, or it may not. There are equally good models, as far as fitting the data.

    So I think it is speculation and liable to mislead readers, to assert that time does not exist before big bang.

    The other issue is how one should regard cosmologists currently studying cosmology models that extend back before. Should one flatly declare them not to be scientists?

    Well the definition of a scientist is in part membership and status in a community. Who is recognized by peers and colleagues.

    I think it would be healthy to do an objective reality check at this point. The relevant professional association is the GRG society (General Relativity and Gravitation). It holds large international meetings every three years, elects officers, awards the Xanthopoulos prize for research in GR/gravitation/cosmology. A good check would be to look at who gets invited to give plenary talks, who gets honored for their work by special awards, who gets elected president of the association.

    I shouldn't have to point out the obvious, but if you look you will find that the scientists who are exploring nonsingular cosmic models (typically bounce models) are in very good standing indeed! :biggrin:

    BTW I just did a keyword search at arxiv and compared the number of bounce-related preprints in two four-year periods 2001-2004 versus 2005-present. There has been an order of magnitude increase. Jumped from 91 to 774. This is a very rough measure. There has been a comparable jump in citations, again a rough measure.

    One should be very skeptical about which models might or might not be correct. Several recent papers I've seen try to identify observable differences in what models predict---especially subtle effects on CMB and structure formation. But it's clearly too early to make distinctions empirically.

    I don't know of any professional cosmologist who would say at this point that time does NOT exist before big bang. Maybe there are---I simply don't know of anyone who says this. My guess is most professionals would reserve judgment at this point.

    So I don't think the poster I quoted, mgb, is presenting an orthodox or "standard" view, if he declares that time does not exist before bang.

    I would say that there is no scientific reason to declare that it exists and no scientific reason to declare that it does not exist. Should mention, though, that the models that don't break down have the advantage of simplicity---don't have to invent anything new, just run the model back. Occam would like that. But they still need to be tested.

    in case anyone is interested in some of the details:
    about 600 attended--all branches of gravitation science (observational e.g. wave, as well as theory)
    Ashtekar was elected president of GRG at the last meeting
    Bojowald was awarded the Xanthopoulos (split with another quantum gravitist)
    http://www.science.psu.edu/alert/Bojowald5-2008.htm [Broken]
    http://grg.maths.qmul.ac.uk/grgsoc/xanthrules.html [Broken]
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  17. Oct 1, 2008 #16


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    An interesting debate is wether theories about something that is fundementally unobservable are science.

    So structure in the CMB that suggests that the big bang wasn't a singulairty is astronomy. But theories about separate universes before or after (if even that's a meaningfull think to say) this one that can fundementally never be tested or observed is different.

    At which point theoretical physics becomes maths or philosophy is symantics or depends on the person in doing your university's phone directory! But I think it is legitimate to regard theories that cannot lead to testable hypothesis as not science.
  18. Oct 1, 2008 #17


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    I have quoted some things you said, mgb, in the preceding post. It is all right to say that the cosmology model based on vintage 1915 GR breaks down at the start (the intial singularity or failure of the model.) We can agree that this shows the familiar classical model has limits of applicability. That's well known.

    It is not all right to say that people studying the newer models which do not break down are not scientists. It is not all right to say that their work is not science, and in particular that it is not gravitational physics.

    Can we agree on that? I hope :smile:

    Hello? We are not talking about theories which cannot lead to testable hypotheses. Maybe you haven't been following current research closely enough for me to discuss this with you. For instance Bojowald's work is aimed at determining what can be learned from the Planck satellite mission. You might read my earlier post mentioning CMB and structure formation.
    Last edited: Oct 1, 2008
  19. Oct 1, 2008 #18


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    Observations of eg. the CMB that show structure in the pre-inflation universe and suggest that there wasn't a simple singularity are obviosuly obervational science.

    Models that propose multiple parralel or serial bounce universes with a singluarity and so no observable consequences are different.

    The OP's question was what happened before the big bang. The point is that in the standard model of a singularity that isn't answerable.
  20. Oct 1, 2008 #19
    Do we KNOW that there was no time before BB, or is it just a guess? Are you saying that BB didn't have a cause, it just happened? Isn't this just like saying "God did it"?
  21. Oct 1, 2008 #20
    Did the universe dwell in the singularity before suddenly starting to expand?
  22. Oct 15, 2008 #21
    I'm not a Physicist (I don't even have a beard:smile:), I'm a newbie Chemist and amateur Philosopher but I have difficulty understanding why there is a problem saying there was time before the big bang. I don't even see why there must be, or how there could be a beginning at all.

    If we define the universe as everything that is, as the name implies, then time is part of the universe because it exists.

    If causality is true, which is a reasonable assumption to make because as far as I am aware no one has ever observed or theorised any other method by which an action could occur, then something must have caused the big bang. So there must have been time enough for the cause to happen, and the cause's cause ad infinitum.

    Lets take the law of entropy as true as well. This means that eventually all the matter and other energy in the "universe" (or Self Contained Energy System, SCES, to account for the possibility of something else existing outside our exanding bit) will become homogenous, with nowhere being significantly warmer than anywhere else. It will also probably stop expanding at some point.

    When this happens gravity will probably still be in effect (as far as I'm aware there is no reason for it not to be) and the universe will collapse in on itself.

    If there is a maximum amount of energy it is possible to contain in one section of space, and this threshold is reached, it is reasonable to postulate that it could explode.

    Nothing in this explaination seems outlandish or mind boggling, and I'm sure I'm not the first to come up with this kind of explaination. Please don't think I'm trying to pass off my personal understanding as fact... I'm just puzzled by these problems people have with a time before our SCESs current expansion.
  23. Oct 15, 2008 #22


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    I sympathise. People don't know whether or not time extends before current expansion. There are models that fit the data equally well, some that break down in a singularity right at start, and some that don't. At present there seems no scientific reason to prefer one over the other.
    So it seems obviously speculative to say that time does not exist before big bang.

    It might exist, it might not---we shouldn't pretend to know, or that scientist all think one way about this. In fact they differ. There is a lot of research into non-singular cosmology going on at present.

    But you still run into entrenched opinion, and, as you say, it is puzzling.

    You might like this online cosmology source called Einstein Online, which is an outreach website from Germany's Max Planck Institute---the unit called Albert Einstein Institute (AEI). It is reasonably uptodate. It is a worldclass outfit. And the main author is a PhD physicist who specializes in wide-audience non-technical-style writting. Same first name: Markus Possel.
    I will get the link to his cosmology section.

    Here is the AEI homepage for cosmology outreach:
    If you like cosmology you are going to love this! It's a great source of explanations and clarification of all kinds of cosmo issues.

    And BTW here's a page from the AEI site that addresses just what you were talking about:
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  24. Oct 16, 2008 #23

    The Big Bang Echoes through the Map of the Galaxy



    In the two widest-ranging exercises on mapping the galaxies carried out to date, scientists have made findings that offer serious support for the Big Bang theory. The results of the research were presented at the winter conference of the American Astronomical Society.

    The wide extent of the distribution of galaxies is evaluated by astrophysicists as one of the most important legacies from the first phases of the universe to have come down to the present day. It is therefore possible to refer to the information on the distribution and location of the galaxies as "a window opening onto the history of the universe."

    In their research that lasted several years, two independent teams, composed of British, Australian and American scientists, produced a three-dimensional map of some 266,000 galaxies. The scientists compared the data they collected on the distribution of the galaxies with the data for the Cosmic Background Radiation emitted everywhere in the universe, and made important discoveries regarding the origin of galaxies. Researchers analyzing the data concluded that the galaxies formed where matter that formed 350,000 years after the Big Bang relatively clustered together, and then assumed their shape under the influence of the force of gravity.


    [COLOR="Red"]According to the Big Bang theory, everything began from the explosion of a point of infinite density and zero volume. As time passed, space expanded and the gaps between heavenly bodies grew.[/COLOR]

    The findings in question confirmed the Big Bang theory, which states that the universe began from the explosion of a single point of zero volume and infinite density some 14 billion years ago. This theory has constantly been confirmed by tests consisting of decades of astronomical observations, and stands unrivalled on the most solid of foundations. The Big Bang is accepted by the great majority of present-day astrophysicists, and constitutes scientific verification of the fact that God created the universe from nothing.

    In its ten-year-long research, the Anglo-Australian Observatory in the Australian state of New South Wales determined the positions in space of 221,000 galaxies by means of a three-dimensional mapping technique. The survey, which was performed with a 3.9 meter diameter telescope at the observation post, was almost ten times larger than any previous such study. (1) Under the leadership of Dr. Matthew Colless, director of the observatory, the team of scientists first determined the position of galaxies relative to one another and the distances between them. Then they modeled the distribution of the galaxies and studied the minute variations in that model in great detail. The scientists offered their research for publication in the journal Monthly Notices of the Royal Astronomical Society.

    In a similar study carried out by the Apache Point Observatory in New Mexico, USA, the positions of some 46,000 galaxies in another region of space were similarly mapped and their distribution was investigated. The study, involving the use of a 2.5 meter diameter Sloan telescope, was carried out under the leadership of Daniel Eisenstein of the University of Arizona, and is to be published in the Astrophysical Journal. (2)

    The results obtained by the two groups were announced during the winter meeting of the American Astronomical Society in San Diego, California, USA on 11 January, 2005.


    [COLOR="Red"]Data obtained from the COBE satellite in 1992 revealed minute fluctuations in the emission of Cosmic Background Radiation.[/COLOR]

    [COLOR="DarkRed"]An Important Confirmation[/COLOR]

    The data obtained as the result of long and careful work confirmed estimates made decades ago in the field of astronomy regarding the origin of the galaxies. In the 1960s, theoreticians estimated that galaxies may have seeded in regions where matter massed in a slightly higher concentration shortly after the Big Bang. If that estimate is correct, then the seeds of the galaxies should be capable of being observed in the form of tiny fluctuations in heat levels in the remains of radiation left over from the Big Bang and known as Cosmic Background Radiation.

    Cosmic Background Radiation is heat radiation that only began being emitted 350,000 years after the Big Bang. This radiation, emitted everywhere in the universe, represents a snapshot of the 350,000-year-old universe, and can be observed rather like a fossil in the present day. This radiation, first discovered in 1965, was recognized as definitive proof of the Big Bang with various studies and observations, and was investigated in great detail. Data obtained from the COBE (Cosmic Background Explorer) satellite in 1992 confirmed the estimates made in the 1960s and revealed that there were ripples in the Cosmic Background Radiation. (3) Although at that time a partial link had been determined between these and the formation of the galaxies, that link could not be definitely shown until now.

    However, that important link was constructed in the latest studies. Colless and Eisenstein's teams determined a match between the ripples seen in Cosmic Background Radiation and those in the distances between galaxies. It was thus established that the galaxies seeded in places where matter that emerged 350,000 years after the Big Bang concentrated in slightly higher densities.

    At a press conference on the subject, Dr. Eisenstein said that the way galaxies are scattered across the sky now corresponds to the sound waves that gave rise to that distribution. Researchers think that gravity affected the waves and shaped the galaxies. Eisenstein made the following comment:

    "We regard this as smoking-gun evidence that gravity has played the major role in growing from the initial seeds in the microwave background (left over from the Big Bang) into the galaxies and clusters of galaxies that we see around us." (4)

    In a statement to the AAP news agency, Russell Cannon, from the other research team, noted that the findings were of the greatest importance, and summarized the significance of the research in these terms:

    "What we've done is show the pattern of the galaxies, the distribution of the galaxies which we see here and now, is completely consistent with this other pattern that's seen in remnants of the big bang…" (5)

    Findings were also obtained from the study regarding the levels of matter and energy that constitute the universe, and the universe's geometrical form. According to these, the universe consists of 4% normal matter, 25% dark matter (matter that cannot be observed but that is calculated to exist), and the rest of dark energy (mysterious energy that leads to the universe expanding faster than expected). As for the geometrical shape of the universe - it is flat.

    [COLOR="DarkRed"]Support for the Big Bang[/COLOR]


    [COLOR="Red"]Sir Martin Rees[/COLOR]

    The findings made in these studies have further strengthened the Big Bang theory. Dr. Cannon said that the research added serious weight to the Big Bang theory about the origin of the universe and emphasized that support in these words:

    "We've known for a long time that the best theory for the universe is the Big Bang -- that it started in some enormous explosion in a tiny space and it expanded ever since." (6)

    In a comment regarding the studies, Sir Martin Rees, the well-known Cambridge University astronomer, noted that despite using different statistical techniques and observations, the teams had arrived at the same conclusion, and that he regarded this as an indication of the results' accuracy. (7)

    Physicsweb.org, one of the most important physical sciences portals on the Internet, commented that the studies "provide further evidence for the standard big bang plus inflation model of cosmology." (8)

    Scientists learned that the universe had a beginning (Big Bang) and was expanding (Inflation) by reading the radiation and heavenly bodies in space thanks to the possibilities of modern science. However, these fundamental data are not at all new to mankind. Mankind has been reading these two facts, which scientists were only able to read in the depths of space in the 20th century, in the Qur'an for the last 1,400 years.

    Two Basic Pieces of Information about the Standard Cosmological Model Are Provided in the Qur'an

    In the Qur'an, and in the Torah and the Bible that were corrupted after their revelation, God has revealed that the universe and all matter were created out of nothing; in the Qur'an, the only text that has not been corrupted, He reveals one other miraculous secret that the universe is expanding.

    The way the universe came into "being" from "non-being" is reported thus in the Qur'an:

    [COLOR="Blue"]He is the Originator of the heavens and the earth.[/COLOR] (Qur'an, 6:101)

    The expansion of the universe, one of the main areas of research of modern science, is revealed in this verse:

    [COLOR="Blue"]And it is We Who have constructed the heaven with might, and it is We Who are steadily expanding it. (Qur'an, 51:47)[/COLOR]

    As we have seen, two elements of the standard cosmological model, the Big Bang and Inflation, were reported in the Qur'an at a time when the means of astronomical observation were very limited. This represents clear proof that the Qur'an was revealed by God. The findings of modern science are in complete agreement with what is related in the Qur'an, and these latest studies once again draw attention to that close compatibility.

    1- "Galaxy patterns reveal missing link to Big Bang," January 12, 2005, online at: [url]http://info.anu.edu.au/mac/Media/Media_Releases/_2005/_January/_120105redshift.asp[/url]
    2- "Detection of the Baryon Acoustic Peak in the Large-Scale Correlation Function of SDSS Luminous Red Galaxies", submitted to Astrophysical Journal on December 31st, 2004. See. Sloan Digital Sky Survey, "THE COSMIC YARDSTICK--Sloan Digital Sky Survey astronomers measure role of dark matter, dark energy and gravity in the distribution of galaxies," January 11, 2005, online at: [url]http://www.sdss.org/news/releases/20050111.yardstick.html[/url]
    3- "Galaxy patterns reveal missing link to Big Bang", January 12, 2005
    4- Deborah Zabarenko, "'Cosmological ruler' helps measure the universe," January 11, 2005, online at: [url]http://www.reuters.com/newsArticle.jhtml?type=scienceNews&storyID=7297222[/url]
    5- "Scientists Score Galaxy Breakthrough," AAP, January 13, 2005, online at: [PLAIN]http://www.macnewsworld.com/story/Scientists-Score-Galaxy-Breakthrough-39646.html[/URL]
    6- "Scientists Score Galaxy Breakthrough", AAP.
    7- Maggie McKee, "Big bang sound waves explain galaxy clustering," NewScientist.com News Service, January 12, 2005, online at: [PLAIN]http://www.newscientist.com/article.ns?id=dn6871;[/URL] Mark Peplow, "Echoes of Big Bang found in galaxies," [email]News@nature.com[/email], January 12, 2005, online at: [url]http://www.nature.com/news/2005/050110/full/050110-8.html[/URL]
    8- "Galaxy surveys put cosmology on sound footing," January 12, 2005, online at: [url]http://physicsweb.org/articles/news/9/1/7/1[/url]

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