Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The time before the big bang

  1. Aug 8, 2012 #1
    After reading a few chapters of an astrophysics/ cosmology book, I took some time to think about the big bang and what existed before it. After thinking, I thought, "What if the big bang wasn't the beginning of existence? What if it were a just a big event that happened over the course of the existence?" Eventually, I came up with a hypothesis that maybe, the big bang was caused by a sort of hypernova? Before the big bang, there may have been a supermassive object like a star or blackhole. An object millions of times larger than any we know of. What if this object were to collapse into itself under its own gravity and create a neutron star. The excess gases and debris would be flung out into space and eventually form small nebulae then stars and eventually, the debris from the supernovae would form planets and so on, which would get us to the present. I am sure this sounds completely ridiculous, but I am not an expert on cosmology (I am only 17), but if anyone has any opinions on this, please let me know. Thank you
  2. jcsd
  3. Aug 8, 2012 #2


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    It has become a common focus of research by professional cosmologists to work on "nonsingular cosmology" models where there is time and existence before the big bang, and what was called the big bang is simply the start of this episode of expansion which we are witnessing and trying to understand.

    So you can find out what models other people are researching just by looking at online schedules of talks at the major international conferences that cover GR and cosmology. there are two main conferences, each of which is triennial (held every three years). they are called the Marcel Grossman meeting (they just had MG13 last month in Stockholm, over a thousand scientists participated) and the GR conference (GR20 will be held in Warsaw next year in early July. I guess attendance will be over 700).

    MG13 had a special session devoted to nonsingular cosmology models. And it had four other sessions that were partly devoted to bounce cosmology and partly to quantum gravity and related stuff.
    It is an active line of research and a lot of people are working on it. And a lot of people are interested in figuring out OBSERVABLE CONSEQUENCES of a bounce, traces or features of the CMB that they can look for in the sky.

    the bounce idea is more popular with the professionals than your hypernova idea.
    A hypernova is kind of like an explosion in preexisting static geometry---a fixed empty space.
    That is not how they picture expanding geometry cosmic models. You know that GR is first and foremost a theory of dynamic geometry. It explains why geometry is (in many familiar situations) nearly Euclidean and why in other situations it is not. It describes how, if geometry is started off expanding it will continue although it may slow down. And the stuff, the matter, may not be moving in any ordinary sense, it may not be getting anywhere, just everything getting farther apart. Distances can expand uniformly without objects changing relative position. So it is that kind of distance expansion that they have to explain---not an explosion.

    It turns out that if you quantize GR, get quantum versions of the equations of GR or of cosmology, gravity can turn repellent at very high density, so gravitational collapse leads to a rebound. A singularity never develops. So that is one version of nonsingular cosmo----one type of cosmic model. It is one quite a lot of people work on and that got discussed a bunch at the Marcel Grossman meeting in July.

    It's still early days. There are no final conclusions about what was before the start of expansion and what gave it its big start. Personally I am not ruling anything out. I wouldn't even reject the idea of a hypernova, or that a collapse to a black hole caused a bounce resulting in a new expanding region of spacetime. At this point all the ideas are on the table AFAICS.

    But stay tuned. Next year we will see what gets attention at the other big triennial meeting: GR20 in Warsaw. The schedule will be posted online. Also summaries of the talks. A lot of people want to know exactly what you are curious about: what could have led up to the start of this geometric expansion that we're part of.

    You should realize that distances to most of the galaxies we can see with telescope are currently increasing faster than c. Geometric expansion can do that. Flying debris from an explosion can not. It's different.
    Last edited: Aug 8, 2012
  4. Aug 8, 2012 #3
    Would you happen to know of any books or articles with information about their work? I would like to read more into this.
    Thank you
  5. Aug 8, 2012 #4


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    The most active area in bounce cosmology is called Loop Quantum Cosmology.
    A kind of leader or elder statesman in LQC is Abhay Ashtekar. He has occasionally written wide-audience non-technical articles on LQC.
    But most of his writings are at least partly mathematical. They may have accessible intuitive sections at the beginning and end: the introduction section and the conclusions section. I can't think of any one article in particular.
    Here are all his articles:
    When I look down the list I see one from May 2010 that might be accessible

    Here's an idea! Here's the program of talks at the Loops 2011 conference in Madrid. They have some videos of people's talks and also some PDFs of their slides. The talks marked "plenary" all seem to have video versions you can click on.
    Click on "scientific program" on the lefthand side of the page
    and scroll down to Wednesday. Ashtekar gave a talk then.
    If you click on the talk title you get a page with a video insert (which can be expanded to fill the screen)

    But I just watched some of it. It is too technical to serve as an introduction.
    this is embarrassing. I don't know a good intro to LQC at beginner level.
    I think I will get some sleep and think about this tomorrow. Maybe you could check back in 12 or 16 hours to see if I or someone else has come up with a good suggestion.
    Last edited: Aug 8, 2012
  6. Aug 8, 2012 #5
    Try here :http://en.wikipedia.org/wiki/Cyclic_model

    for a brief discussion of cyclic cosmological models.

    If you find it of interest, consider the Steinhardt Turok book THE ENDLESS UNIVERSE, a
    book for the general public, no math. I got a used copy from Amazon....less than $10.

    These guys are respected physicsts and their explanations and insights in the book will really give you a good conceptual understanding of how a cyclic universe might work. There
    are of course other cyclic models and no one knows if any are possible or not.
  7. Aug 8, 2012 #6


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Indeed Steinhardt&Turok are respected! And their idea got a lot of interest before 2006. Not so much recently.
    Personally I have very high regard for Paul Steinhardt. Lately I dont see him doing very much with the old clashing branes idea though. Excellent scientists can come up with ideas that don;t make it.

    and there could always be a revival of interest!

    But look at the program at the Marcel Grossmann meeting MG13.
    These big international triennial conferences are a good gauge of what the professionals are currently taking seriously and are interested in. I don't see the S&T "cyclic" branes-banging -together scenario making any showing at all.

    The next test would be next year at the GR20 meeting. We will see if brane-clash cosmology shows up at Warsaw.

    Ultimately professional herd behavior does not mean anything final about Nature. Both individual scientists and herds of them can be wrong. But you've got to notice, still.

    The idea was already in decline in 2006 when S&T wrote that popular book about it. I think now it lives more in the public imagination than in the world of working cosmologists.But as I say, we will see next year.
    Last edited: Aug 8, 2012
  8. Aug 8, 2012 #7
    I will definitely look at these readings. Thank you guys very much for this information. It is a lot of help.
  9. Aug 8, 2012 #8
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook