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

I have a little problem with the big bang

  1. Dec 31, 2008 #1
    I know it's the popularly accepted theory of how everything began, and for the moment, let's assume it's true. What I'm trying to understand is the red shift in terms of the farther away an object you observe is, the farther back in time you are seeing it. The further away objects are the greater is the red shift. Thus, if we someday achieve the ability to see all the way back to "the beginning", what would we see?

    My thinking pushes me towards the idea that if the most distant objects are racing away from us the fastest, then aren't we really "seeing" them in the state they were in right after the big bang? It makes sense. Right after the big bang things were all expanding away from each other at very rapid rates. However, galaxies didn't form until sometime after the big bang, after all the plasma coalesced and formed matter which in turn formed solar bodies, galaxies, etc.

    So, if when we see objects about 15 billion light years away, the average estimate of the age of our universe, does that imply that the only way they could have gotten that far away from us is if they were traveling at or near the speed of light for the past 15 billion years? That doesn't make sense.

    It's almost as if the universe is too big for the matter in it to have expanded so great a distance over such a short period of time. I'm not so sure the red shift means what we think it does. It's almost too convenient of an explanation to compare it to the doppler effect for light. I think that for objects to have gotten so far away in the amount of time we think it took, then those objects would initially have had to be traveling at speeds greater than the speed of light, at least for some finitie period of time.

    Time is the puzzler here. What if things were traveling greater than the speed of light for some period right after the big bang? Relativity urges us to think that time slows down as we approach the speed of light, where it even stops entirely right at the speed of light. But at speeds greater than the speed of light, could that imply then that time may in fact go in reverse? In other words, objects will arrive at locations before they actually got there. A seeming paradox.

    Any help or discussion about this to help clarify my thinking would be greatly appreciated.
  2. jcsd
  3. Dec 31, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Just to clarify, BBT doesn't make any claims about any sort of "beginning of the universe". BBT claims that the (observable) universe was once incredibly dense and went through a phase of rapid expansion (a 'big bang'). But BBT does not speculate about what may or may not have existed before that phase.

    This actually has nothing to do with the big bang; this is just a property of the expansion of space, which could happen even without a big bang.

    According to BBT, you can't: the observable universe was originally opaque. It took a while before things cooled down enough for the universe to become transparent overall. What would we see if we looked back this far? Cosmic background radiation.

    You have the wrong idea about expansion; it has nothing to do with how matter 'travels'. In fact, relativistically speaking, such a notion doesn't even make sense. (But I will take my best guess at what you might mean by such a thing)

    Expansion of space means that distances are inherently increasing over time, regardless of how objects are 'travelling'.

    Incidentally, I believe the most distant redshifts are consistent with distances increasing far more rapidly than the speed of light. (Someone correct me if I'm wrong)

    It's a good thing we don't. :smile: The same effect that causes distances to be inherently increasing also causes light to decrease in frequency.

    No it doesn't. You need to get the idea of absolutes out of your head (e.g. absolute speed, absolute time dilation, etc), and start thinking relatively if you want any chance of understanding this stuff. You should start with special relativity first, rather than jumping into general relativity, because the latter throws in all sorts of awkward new twists.
  4. Dec 31, 2008 #3
    Thank you for the response. If I may, I'd like to comment about how the Hindu story of genesis relates to this topic. I do not claim to be an expert physicist or an expert on Hindu philosophy. But I have done extensive reading on both topics. Plus, since none of us will be around to actually see what happens at the end of time, I think it's safe to comment on some interesting similarities.

    The Hindu idea of creation says roughly that we live in an oscillating universe. That it expands and contracts endlessley throughout all eternity. Of course the only thing that survives each subsequent re-manifestation of a new universe is God, or in the Hindu case, Shiva.

    The Bhagavad Gita even touches on this a little. Anyway, each subsequent recreation of the universe lasts for what they call 100 years of the Brahman. This is an unimaginably long period of time, but it is however, finite.

    "One complete day and night of Brahma: 8,640,000,000 years

    360 of these days is called "One Year of Brahma": 3,110,400,000,000 years

    100 of these years constitute the life of Brahma called a Maha Kalpa: 311,040,000,000,000 years

    At the end of a "Maha Kalpa" or cycle of creation, Shiva manifests his destructive influence and the universe is dissolved. [Actually the entire universe becomes spiritualized.] The ancient texts call this the 'cosmic dissolution'. All the levels of the manifest universe disappear. After a great cosmic rest cycle, another creative cycle begins as a new Brahma emerges out of the navel of Narayana and the universe is created anew.

    8,640,000,000 = one day of Brahma
    3,110,400,000,000 = one year of Brahma
    311,040,000,000,000 = one hundred years of Brahma

    add them all up and you get

    314,159,040,000,000 as a value of pi to 14 decimals 3.14159040000000"

    A Pythagorean Value of Pi

    To me this is a little more than interesting or coincidental, but that's just me. And if our current universe is about 15,000,000,000 years old then we still have quite a long time left before this universe dissolves and a new universe emerges. In fact we have about this many years left: 311,025,000,000,000. Is this enough time for an entire universe to come into being, exist and collapse back in on itself? Maybe some of the real physics gurus out there could weigh in on this one. It seems like an awfully long time to me. Although all the time periods and cycles from which these figures are derived have some basis of observability of cosmic cycles, I find it a bit odd that there should be such a close relationship to pi, and maybe I shouldn't find that odd?

    In Hindu, their main diety has three different names: Shiva, Vishnu and Krishna. Shiva is the only nonmaterial entity to survive each subsequent destruction of an existing universe and creation of a new universe. He is often portrayed as a four armed figure with a small flame in one of his transcendental hands and either a conch shell or a drum in the other. The fire represents the eventual collapse and destruction of each present universe. The drum or conch shell symbolizes the sound of creation as each new universe springs into existance. And it is even quite possible that each subsequent universe is different from the previous one and has its own unique set of physical laws of nature. The laws of nature we are still in the process of discovering about 'this' universe may be completely invalid in the next one. That is to say, perhaps F=MA, E=IR and 'you can't push a rope' might only be the way things work in 'this' universe. With each new universe, thinkers must puzzle out the physical laws and constants anew.

    Now I'm not saying I believe any of this, but what strikes me as pretty amazing is the fact that these Hindu thinkers came up with this idea of an oscillating universe about 6,000 years ago, long before telescopes or super computers or any kind of modern technology we all take for granted nowadays. This implies that there is enough matter in the universe to cause its eventual gravitational collapse. In fact, the balance is perfect; perfect enough for this cosmic birth and death cycle to continue throughout all eternity. But there are several ideas about how things work. Scientifically speaking though the ones that stand up to scutiny and can be validated with observations and experimentation over time are the ones that guide our thinking and define 'conventional wisdom'. Conventional wisdom almost seems like an oxymoron since it is always changing with each new discovery. At one time humans thought the earth was flat and that F = MA dictated our actions and limitations. But then Einstein was born and our thinking changed again.

    It has always amazed me that the Hindu story of Genesis addresses the concept of eternity in a more complete way than the Christian story of Genesis does, or at least in a more poetic way. In the Christian version of Genesis, God created the universe in 6 days and rested on the 7th and that's pretty much it. There is no explanation of what came before and what might come after. I am in awe of these ancient sages who on their own, pondering the great mysteries and staring at the heavens, came up with such a sophisticated and elegant idea of how things might be put together and fit into the continuum of time.

    No one really knows how the universe began or how it will end, but I find the Hindu story the most appealing to me, as stories of creation go. It even explains the Big Bang, so to speak. My study of theology has often surprised me in how some stories of Genesis rival many modern theories of creation from the disciplines of theoretical physics and quantum mechanics. The Heizenberg Principle itself puts forth the idea that no one can ever really be 100% certain of anything, even if you are certain that you are. To 'know' one thing is to be uncertain of another.

    I enjoy comparing different ideas about creation with each other. Please don't think of me as some kind of religious fanatic. I am not, in fact I am a failed Catholic and am probably a confused aetheist at this point in my thinking and will regret my lack of faith once I die. However, I am the kind of person who likes to question things and I don't see the harm in raising these ideas in this forum at large. I am not on trial here and although my candor may reveal many gaps in my logic, I find the freedom of expression here to be refreshing.

    If anyone can add more to the Hindu story please do. I know I did a very bad job of relating it here.

    I used to think that the one guiding principle that drives our universe is the tenet that "Equilibrium is an inherent tendency of change". High pressure tends to relieve itself in search of lower pressures. Competing forces are the only things that can trump this idea. That is, the gravity of a star keeps its mass from drifting into space. otherwise the extreme pressues inside a star would seek equilibrium with its surroundings, the vacuum of space, and dissipate. That does not happen because gravity trumps the force of mass under pressure. In fact I think it is true, except for human beings. Equilibrium is not necessarily an inherent tendency of change as far as humans are concerned. We swim against the current.
    Last edited: Jan 1, 2009
  5. Jan 3, 2009 #4
    Last edited: Jan 3, 2009
  6. Jan 3, 2009 #5


    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    I agree that the empirical rational investigation of cosmology and evolution can sometimes lead to a satisfying worldview and a sense of being at home in and at the same time amazed by the universe and natural law. That outcome is a byproduct. One is trying to arrive at empirically testable economical and rational explanations whatever they turn out to be and regardless of the spiritual side-effects.

    And I would also like to accord respect to every seeking spirit, moreover I find one version of the Hindu creation cycle delightful and have enjoyed retelling it to my friends and family. In addition, I suspect that it is probably a good idea to be a lapsed Catholic and confused atheist. It's definitely more interesting than some other spiritual circumstances I can think of.

    But there is a problem of orderly partition of discourse. It has been found to work better if we compartmentalize discussion here to some extent. I'm not staff, I speak unofficially but from experience.

    If you can generate questions that we can reply to that are not too speculative, and avoid mentioning spiritual correlatives, then perhaps we can discuss here at Cosmo forum. But it has to be mostly about stuff that has an observational, testable basis. In fact cosmology is a mathematical science. Has to do with fitting mathematical models to observational data. We talk a lot in words, but the underlying Friedmann equations model and the periodic releases of new data are always present in the background. (see Wikipedia about Friedmann equations)

    So this presents a problem. In order to avoid having your threads moved to Social Science (humanities and literature subforum) or to General Discussion, or to philosophy subforum, you will probably have to adapt, and learn to frame our kind of questions, and adopt our gradual chipping away approach rather than leaping to conclusions.

    What preceded the big bang is a scientific question. Nonsingular cosmologies---models that have a bounce instead---are topics of current research.
    But on the whole these lines of investigation are proceeding rather cautiously. A book about this is due out this year, edited by Rudy Vaas, title Beyond the Big Bang, published by Springer press. He will have chapters by some 20 top people. A section of the Paris conference in late June will be devoted to nonsingular cosmology, the 12th Marcel Grossmann conference. If you were to read the book, or attend the conference, I expect you would come away thinking that nothing had happened. I see gradual progress, but I may have different expectations about the gradual pace of scientific research.

    About expansion, Hurkyl already answered you---have a look at the Balloon analogy sticky thread and see if some of the posts there help.

    I don't urge Vaas' book on you, far from it! but here's the publisher's page,

    and a preliminary bit about the MG conference in Paris in June,
    I think session SQG2 might be interesting. Depends on how Lewandowski handles it.
    COT3, with Mario Novello might be good. He has done something on bouncing nonsingular cosmologies. Depends on who he can get to come and deliver papers.
    Otherwise one will have to wait until the GR conference in 2010
    Last edited: Jan 4, 2009
  7. Jan 6, 2009 #6
    I apologize for bringing religion into this. I did not mean to. I am a newcomer to this forum and this is my first post. I did not understand the rules about relious references until recently.
  8. Jan 6, 2009 #7


    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    As I tried to make clear, I have no problem and there is no need to apologize in my direction! :biggrin: I remember once several years ago I told the Hindu creation cycle story here at PF---the version where Shiva is sleeping on the back of a giant serpent who is floating in an infinite ocean and a lotus grows up out of his navel and a little deity called Brahma pokes his heat up out of the lotus and looks around and decides to make Shiva happy by creating the universe, which he does and the two friends enjoy watching the universe for a period of time (a kalpa?) and then Brahma collapses it all back into the lotus which vanishes into Shiva's navel and he goes back to sleep on the giant head of the giant cobra floating in the infinite ocean.

    what I was trying to say was you MUST discipline your brain to think of questions of an empirical science nature, otherwise you will be whisked away to some other part of the universe.

    Here's one idea for you: probably the most prominent currently active Quantum Cosmologist is Abhay Ashtekar. Go read the easiest recent papers by him that you can find. Read only the easy parts. Come back with one or two questions. QC is about figuring out what came before Bang, and constructing computer models of it. He and his grad students have done a lot of that. Here are his recent papers:

    Hey Felonius, I just thought of something! Ashtekar grew up in Maharashtra small-towns. Born 1949. Here's a NYTimes piece:
    If you quantize the classic Gen Rel picture the singularity turns into a "big bounce".
    It's the same story coming around again. That they were telling the children in Maharashtra 25 centuries ago.
    Last edited: Jan 6, 2009
  9. Jan 7, 2009 #8
    I have a little problem with bounce ideas. Why are we 'apparently' the final bounce? There's something just too asymetrical about that.
  10. Jan 7, 2009 #9


    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    You may be visualizing it in an unrepresentative way. Here's a sample of Quantum Cosmo papers.
    What you find here is not particularly asymmetrical.

    What they've been doing a lot of in the past 3 years is you quantize the basic Friedmann model used in all cosmology
    and then you computer-model it, and then you run a whole lot of different cases to see what happens.

    They also have constructed analytically solvable models and checked these against the computer versions.
    And they have been relaxing restrictions like isotropy.

    So the aim is to methodically study quantum gravity versions of the universe around bigbang. You want to study a lot of different possible big bangs (with inflation, without inflation, one-time bounce, infinitely repeating bounce, space flat infinite, space curved finite, different types of toy matter, 3 spatial dimensions Bianchi style and so on.)

    Talon I have seen a lot of papers with a lot of results, but I never saw what you seem to be imagining, namely a finite series of full-blown bang-crunch universes with a final one that does not ever collapse.

    Typically what I've seen is either a one-time bounce
    or else an endless cycling of bounces.
    Do you have a problem? I don't see any asymmetry.
    Last edited: Jan 7, 2009
  11. Jan 7, 2009 #10
    guess I'm a little confused on the bounce idea, I'll have to read up on it. I had the impression of a previous possibly infinite series of universes, expansion, crunch, bounce, expansion, crunch, bounce etc... then our current universe doesn't seem to be headed for a crunch.

    still just a layman, not at your level ;)

    maybe I should rephrase that. Not an infinite series of universes but just our one. with a previous history of expansions, contraction, bounce, expansion... etc.... well that was my impression anyway.
    Last edited: Jan 7, 2009
  12. Jan 7, 2009 #11


    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    I'm just a QC watcher, not a researcher. Can't claim expertise. But I do track the literature and I've never seen what you describe.

    I did see some papers where the bounce event, in computer simulation, involved several successive small bounce+recollapses (almost like a rapid vibration) before finally breaking loose into wholesale expansion and a new universe. But that was not a largescale cycle thing. It was just that the bounce was complicated. There was also a Bianchi case where the bounce occurred in each of 3 dimensions at possibly separate instants of time, but close together. Again a single onetime bounce event, but just somewhat more complex. Not perfectly coordinated.
    These are atypical results, but they do come up.

    However as I say I've never seen a series of full-blown universes with a final one having no crunch. Their models tend to produce either the one-timer or the endless cycle of bounces.
  13. Jan 7, 2009 #12


    User Avatar
    Science Advisor
    Gold Member
    2015 Award

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: I have a little problem with the big bang