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Thread: Alternatives to the Big Bang Theory?

  1. #31
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    Quote Originally Posted by Jeff Root View Post
    Ignoring the acceleration of the expansion, it seems
    clear that the Big Bang looks identical to an explosion.
    So I'd say that it was an explosion. I see no reason
    to think it wasn't.
    If it was an explosion, you wouldn't expect the recessional velocity of a galaxy/piece of debris to speed up wrt you as it gets farther (just Hubble's distance-velocity formula, not talking about acceleration of the expansion).

  2. #32
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    Quote Originally Posted by caveman1917 View Post
    If it was an explosion, you wouldn't expect the recessional velocity of a galaxy/piece of debris to speed up wrt you as it gets farther (just Hubble's distance-velocity formula, not talking about acceleration of the expansion).
    We've been here before with Jeff.

    I think the sticking point here is the interpretation of distance in the distance-velocity formula. For sure, the higher the redshift, the faster the recession velocity. The higher the redshift, the earlier in the history of the universe we are seeing.

    A z=7 galaxy is seen as it was 13 billion years ago, receding really fast. A z=1.4 galaxy is seen as it was 9 billion years ago, receding at a slower rate. As redshift reduces, so does recessional velocity.

    Nowhere do we actually see something with greater proper distance actually receding faster than something with a lesser proper distance - the metric expansion is inferred, rather than observed. What we observe is that the longer the light has been travelling, the faster the object is receding. Objects in the early universe were receding faster than objects in the later universe...

  3. #33
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    Quote Originally Posted by Jeff Root View Post
    The Big Bang sure looks exactly like an explosion to me.
    ...

    In every way, it resembles an explosion exactly.
    Problem #1. Explosions have a definable point in space/time where they begin. The big band at best only has a definable point in time where it began as it happened at evry point in space as far as we can tell.

    Problem #2. Explosions do not seem to speed up, slow down then speed up again. The big bang and the expansion we see now seems to do just that.

    Problem #3. Explosions are not homogeneous. The big bang seems to be very homogeneous.

    Probably more but "exactly" is a very strong word to use on an analogy and I'd have to disagree with you there.

    Quote Originally Posted by Jeff Root View Post
    The words in the parenthesis don't add anything.
    We extrapolate backward in time. The farther back we
    extrapolate, the more compact was the part of the
    Universe we can see now. We can't extrapolate
    accurately all the way back to the very beginning, so
    the "finite" size you refer to is whatever size it was
    at any particular time.
    I think it is better said that our visible universe had a finite size at the start of the big bang. The universe could still be infinite.

    Quote Originally Posted by Jeff Root View Post
    What size is a car as the sheets of metal and parts
    from which to build it are just beginning to arrive at
    the assembly line? Does it have any size at all?


    My understanding is that general relativity works all
    the way back to the beginning, but quantum mechanics
    does not. General relativity isn't aware that particles
    and forces exist. It just knows of mass, energy, and
    spacetime. So general relativity is suspect when it
    predicts a singularity at the beginning.


    I don't think a singularity usually means a broken
    model. It just means a place where some value
    becomes zero, and as a result, other values become
    impossible to calculate.

    -- Jeff, in Minneapolis
    Doesn't a "undefined" answer = broken model? If you have a model that in one or more places does not give you an answer then wouldn't that be broken if you want an answer at those places?

    Models are models not the real world. Our models will always, in my opinion, be broken simply because they are models and not the real thing. They can get more and more accurate but like analogies will always have their limits.

  4. #34
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    Quote Originally Posted by Xibalba View Post
    And despite the theories, how can you be sure of a theory's relation to reality?
    You compare what the theory predicts to observations.

    The big bang theory predicts a blackbody microwave background radiation with a specific temperature. This is observed. It is not just observed by priests. Anyone can observe it if they go to the effort. People even predicted what the temperature would be. The prediction was darn close to what was subsequently measured.

    If there was a big bang, then near the beginning the universe would have been very hot and dense, but it also would have been expanding very quickly, and therefore also cooling. The initial heat would have been enough for atomic fusion to occur, but only for a few minutes, after which it would no longer be hot enough, and fusion would cease. Atomic testing has informed us how fusion works, at what temperatures, and what results from the fusion. A hot, dense, and quickly expanding universe would have resulted in a very specific ratio of light elements. Such ratio of elements is precisely what is observed. To summarize: If there was a big bang, we would see a particular ratio of elements. We do see this particular ratio of elements. This does not "prove" the big bang occurred, but it makes it awfully solid. The big bang is a physical theory that explains why the baryonic makeup of our universe is the way it is. I am unaware of any "alternative theories" that do that.
    Everyone is entitled to his own opinion, but not his own facts.

  5. #35
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    Quote Originally Posted by Jeff Root View Post
    Exactly the same as an explosion.


    The first part of that is exactly the same as an explosion.
    Gravity slows it down in all cases. In some cases, some
    of the bits escape and keep on going. In other cases,
    they don't.

    The second part-- All my books are from the 1980's or
    earlier. I have no idea what this "accelerating process"
    is that you refer to. I've never heard of it, since it
    wasn't discovered until 1998.

    -- Jeff, in Minneapolis
    ? So you have a problem that we didn't have good enough observations to tell that the expansion appears to be speeding up until 1998 and thus you can discount that so the big bang still appears "exactly" like an explosion to you?

  6. #36
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    Quote Originally Posted by Xibalba View Post
    Well, I know the term "explosion" doesn't describe accurately the Big Bang theory, but I was using it only because the word "Bang" is in the name of the theory, even though it is not representative of the theory itself.

    I dislike the Big Bang theory because it involves an infinitely small starting point, of infinite mass.
    Get that out of your head. The big bang theory does not involve an infinitely small starting point. That is extrapolating further back then the Big Bang theory is scientifically meant to go.

    Quote Originally Posted by Xibalba View Post
    Infinity doesn't exist, in my very humble opinion, except in mathematics, where we need it for approximations, and other stuff, but reality does not include infinity.
    And the universe doesn't care about your humble opinion. The universe may or may not be infinite in size. Energy may or may not condense to an infinitely small point at the centre of a black hole. The universe seems to have a start in time but it may be cyclic and is infinitely old but our current cycle has a finite amount of time or the universe may have some start in time but will become infinitely old.

    Just because you have a gut feel that infinities don't exist doesn't mean they don't and there is more reason to believe that there are infinities then not because if you remove them then you have to answer where the boundaries come from and what those boundaries actually mean. Like when will the universe end? Even if the universe keeps expanding will "time" ever end? In one sence

    Quote Originally Posted by Xibalba View Post
    I've heard of the multiverse theory, or hypothesis, but that only distances the question. It's okay if our universe is a bud of another greater universe, but where does that "greater universe" come from?
    You are stepping out of science and into philosophy.

    Quote Originally Posted by Xibalba View Post
    And despite the theories, how can you be sure of a theory's relation to reality?
    By testing them. Currently the big bang theory is doing pretty well. Just like the theory of gravity is doing pretty well. And the theory of evolution is doing very well.

    Quote Originally Posted by Xibalba View Post
    Given we cannot reach the "end" of the universe (assuming that the expansion of our universe is faster than light, and that the principles of thermodynamics are inviolable), how can we prove anything our mind can extrapolate?
    Again science isn't about proofs. Science is about providing the best answer and models given the current set of observations. It is always subject to change given new data or even just a better model/theory.

    Quote Originally Posted by Xibalba View Post
    The BB theory has only one good side : it brings closer in time the moment of unknowledgeableness. Given that, creationism is better at doing it.
    Opinion and an opinion based off of a bad understanding of the theory in question. If you are looking for places where science has not yet found an answer to something to give you a place for you to hide your supernatural beliefs in then be warned if you try to hide them in the current holes of our understanding then you are going to be very disappointed when those holes are filled by science.

  7. #37
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    Quote Originally Posted by speedfreek View Post
    We've been here before with Jeff.

    I think the sticking point here is the interpretation of distance in the distance-velocity formula. For sure, the higher the redshift, the faster the recession velocity. The higher the redshift, the earlier in the history of the universe we are seeing.

    A z=7 galaxy is seen as it was 13 billion years ago, receding really fast. A z=1.4 galaxy is seen as it was 9 billion years ago, receding at a slower rate. As redshift reduces, so does recessional velocity.

    Nowhere do we actually see something with greater proper distance actually receding faster than something with a lesser proper distance - the metric expansion is inferred, rather than observed. What we observe is that the longer the light has been travelling, the faster the object is receding. Objects in the early universe were receding faster than objects in the later universe...
    But isn't this what we found out in 1998...that there are points in earlier in the universe that are receding at a slower rate then points later on, after you remove the "later on" points effect from the earlier points?

  8. #38
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    The others here have more than taken care of the other part of this post, however there are a couple of points....

    Quote Originally Posted by Xibalba View Post
    Well, I know the term "explosion" doesn't describe accurately the Big Bang theory, but I was using it only because the word "Bang" is in the name of the theory, even though it is not representative of the theory itself.
    You do know that originally, the Term "Big Bang" was coined by opponents of the Big Bang and was derisive, right?

    Quote Originally Posted by Xibalba View Post
    I dislike the Big Bang theory because it involves an infinitely small starting point, of infinite mass. Infinity doesn't exist, in my very humble opinion,...
    Well, then, you should have no problem with the Big Bang Theory. After all, it doesn't start until after 10-43 seconds after the start of the universe and does not include the initial singularity. The Big Bang is a cosmological model and does not include any infinities (it does contain singularities at the center of a black hole, by virtue of including, and, indeed, being driven by, General Relativity). What you are thinking of, and what is not part of the Big Bang model, is cosmogony , which is the study of how the universe, or universes, or whatever your particular creation story, came to be.

  9. #39
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    Several reminders

    First, I would remind people of BAUT's exceptions to the no-religion rule

    B) Focused, polite discussion of concepts such as creationism and "intelligent design" which bear direct relevance to astronomy and science, for the purposes of conversing about and addressing misconceptions.

    C) Focused, polite discussion of the difference between astronomy (including cosmology) and religion
    So far, the discussion has seemed to stay within those limits; please keep it that way.
    Quote Originally Posted by Jeff Root View Post
    I'd prefer to argue whether or not the Big Bang was an
    explosion, rather than say anything about the acceleration
    of the expansion.

    Ignoring the acceleration of the expansion, it seems
    clear that the Big Bang looks identical to an explosion.
    So I'd say that it was an explosion. I see no reason
    to think it wasn't.

    -- Jeff, in Minneapolis
    Jeff Root,

    You are rapidly hijacking a thread in Q&A with your own ideas about the Big Bang. This thread is to answer the OP's question as to the existence of alternative theories, and to provide Mainstream answers to that question. Some further expansion of their question is allowed, but you are doing much more than that and are rapidly approaching the advocacy of non-mainstream ideas in Q&A. If you want to discuss your questions about the Big Bang, start your own thread in an appropriate part of BAUT.

    My advice to Jeff also applies to others.
    At night the stars put on a show for free (Carole King)

    All moderation in purple - The rules

  10. #40
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    Thanks all for making clear some facts about BBT.

    I want to make something clear, too:

    I do not believe in creationism, despite what you seem to think.

    Now that it's clear(er) that the BBT does not include the starting point of our universe, but begins at 10^-43 seconds, would there be other theories, or hypothesises that needs further testing to eventually become theories or fail at it, that would explain, or try to, the very beginning of the universe? I've read about superstrings theory, but I don't remember reading anything about the starting point of the universe, even though this hypothesis tries to unite GR and QM. I know what SST is worth, now, and I don't think it is much, it was only used as an example.

    Another point I'd like to make clear : If the universe is space and time as we know it, then how can you go as far back as 10^-43 s? At this point, I think, the dimensions have melted together, and space/time along with the attractive forces form a "whole", then how can time be calculated?

    I think I also get the point of the "infinity" of the universe. It may not be infinite in volume, but there are no borders because it is all there is...?

    Also, even if the universe's expansion is accelerating, it might not become infinitely old if the fabric of it is torn apart by the stretching of it. Yes? No? Maybe?

  11. #41
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    String based models do give one possible mechanism for a beginning - brane collisions. But given that there is no evidence for Strings and not very good underpinning theory about how branes might collide this can safely be put in the "Highly Speculative" box.

    As for dimensions and so on 'melting' - nope. At that point in time our models still work. As we go further back forces unify, until the point where it is possible gravity unifies with the other forces. Just before we have gone this far back our models are well and truly broken. We don't know what will replace them, only that it has to replicate their predictions in the low energy domain and unify GR and QM in some larger framework. Since we don't even know what the framework might look like yet it is early to speculate what is says about the start of the universe.

    All we know is that the metric is expanding. We do not know if it is stretching in a way that might imply a rupture. Extrapolating into the far future is basically pointless because we don't understand the now well enough. We do not know what is driving acceleration of expansion, we do not know if it will continue, reverse or just stop. So the answer is basically "Fweh". To use one of my favourite analogies - if you have never seen a cat and you watch a kitten grow for a short time then you might be tempted to hypothesise that one day the entire world will be filled by mega-kitten. Your ignorance of the cause and evolution of the effect (kitten growth) would lead you to extrapolate beyond the bounds of your simple model (Kittens grow fast).

  12. #42
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    Quote Originally Posted by Xibalba View Post
    If the universe is space and time as we know it, then how can you go as far back as 10^-43 s? At this point, I think, the dimensions have melted together, and space/time along with the attractive forces form a "whole", then how can time be calculated?
    There are theories for that.

    Quote Originally Posted by Xibalba View Post
    Also, even if the universe's expansion is accelerating, it might not become infinitely old if the fabric of it is torn apart by the stretching of it. Yes? No? Maybe?
    The best-fit model of the observed expansion history has the vacuum energy density remaining constant even as the distance between faraway clusters is increasing in every direction. So the 'fabric' seems to remain whole, even though it's expanding (now with a slight acceleration - observations confirm the expansion was decelerating for the universe's first ~6 billion years).
    Everyone is entitled to his own opinion, but not his own facts.

  13. #43
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    Quote Originally Posted by Selfsim View Post
    Quote Originally Posted by Jeff Root View Post
    Exactly the same as an explosion.

    The first part of that is exactly the same as an explosion.
    Gravity slows it down in all cases. In some cases, some
    of the bits escape and keep on going. In other cases,
    they don't.

    The second part-- All my books are from the 1980's or
    earlier. I have no idea what this "accelerating process"
    is that you refer to. I've never heard of it, since it
    wasn't discovered until 1998.
    Ok .. so your emphasis is on the phase before ~10-36 seconds.
    No, not at all.

    My "emphasis" in this thread has been how the Big Bang fits the
    meaning of the term "explosion". Different explosions proceed
    in different ways. The Big Bang was unique to our experience.
    We know of no other explosion like it. We also are ignorant of
    how it happened, and what the conditions were at very early
    times, including the time you reference. I don't have much to
    say about times as early as that, except to assert that we don't
    know what was happening then.

    The thing is, the Big Picture of the Big Bang is that everything
    in the Universe is flying apart from a more condensed state, in
    which it was very hot and very energetic. That is a description
    of an explosion.

    Quote Originally Posted by Selfsim View Post
    I guess that's OK, but the OP seemed to be requesting a
    comparison of theories about the 'creation of the universe'..
    not just a description of the first and least known part of it (?)
    The term 'explosion' makes it difficult to dislodge the concept,
    in order to explain what came next, which is arguably, the
    reason for preferring the SCM over the alternatives.

    Perhaps I've misread the question. (Apologies, if this is so).
    The original poster used the term "explosion" to refer to
    the Big Bang. That was asserted by others to be wrong.
    I simply disagree with them. I say that the term is apt.

    No reason has been given to think that the Big Bang was
    not an explosion.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  14. #44
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    Quote Originally Posted by Van Rijn View Post
    Quote Originally Posted by Jeff Root View Post
    Exactly the same as an explosion.
    That doesn't make sense to me.

    If you have a line with each point on the line separated
    by one unit, then on a time progression increase the
    separation to two units and so on, I don't see how that
    can be reasonably be called an explosion.
    What is a line? Could you send me one in the mail if
    postal regulations didn't prohibit mailing explosives?

    What is a point? Could you send me a box of points?
    I presume that if they aren't in a line, they won't be
    explosive.

    What you described is a geometrical description of uniform
    expansion over time through one dimension of space. It has
    features in common with a description of an explosion. But:

    Explosions do not necessarily involve ideal geometric objects.

    Explosions are not necessarily one-dimensional.

    Explosions are not necessarily uniform in time or space.

    However, I see no reason why the geometrical scenario
    you describe could not be termed an explosion. Visually,
    it looks like an explosion:

    http://www.freemars.org/jeff2/expand3c.htm

    Although it is an extremely pared-down, simplified and
    geometricised explosion, it is still an explosion.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  15. #45
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    Quote Originally Posted by Shaula View Post
    Jeff, suggest you draw a diagram of how stuff is thrown out
    from an explosion. Then how redshift implied velocity works.
    Look at the difference.
    I fail to see a difference.

    Quote Originally Posted by Shaula View Post
    Look at your conclusions. Realise that you can only say
    "The Big Bang was an explosion" if you assume we are
    near the centre.
    I do not assume that we are near the center.

    The Big Bang was an explosion.

    There, I said it. Now what?

    Quote Originally Posted by Shaula View Post
    I also suggest you read something written after 1980.
    Things do move on in cosmology.
    The acceleration of the expansion discovered in 1998 is
    something I should have predicted. My ATM hypothesis
    implies acceleration, but I didn't see it. My hypothesis
    may be completely wrong, but the acceleration of the
    expansion fits it perfectly.

    Quote Originally Posted by Shaula View Post
    The other points:
    The words in parenthesis were there because an infinitely
    small point is smaller than the universe. I was highlighting
    that this is NOT where the theory goes back to.
    GR breaks down because at those scales you need to
    include QM. It is not a complete model and we know that.
    I'm pretty sure that general relativity does not break down.
    But since we do need to include quantum mechanics, and
    can't, the cosmological theory does "break down". As we
    look back farther and farther, the incompleteness of the
    theory becomes more and more apparent.

    I guess my complaint about your parenthetical comment
    is that it seems to say something about the Universe, but
    is actually about the incompleteness of the theory.

    Quote Originally Posted by Shaula View Post
    I am not sure what you are trying to do with your post - propose
    an ATM where the BB is an explosion in pre-existing space? Push
    models beyond their limits and declare that they are bad models
    because they are not universally applicable? Argue with words
    when maths is more precise?
    What I am trying to do is disagree with the idea that the Big
    Bang was not an explosion. It clearly was.

    Quote Originally Posted by Shaula View Post
    Every time I see "It looks like" I die a little inside. I once saw
    a cloud that looked like a horse. Doesn't mean it was one.
    All of science -- every single bit of it -- is based on what
    things look like. You are asking me to believe that the Big
    Bang was not an explosion because it doesn't look like an
    explosion.

    But of course it does look like an explosion.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

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    Quote Originally Posted by Xibalba View Post
    Hi,
    I'm aware of the Big Bang theory, but not very fond of it.

    Is there other explanations of the creation of the Universe, other than a big "explosion"?
    I wish the science community would have "coined" a different term than Big Bang. I wish the science community could change that term to something else. If we have now decided that Pluto is no longer a planet then we can surely change the name of Big Bang Theory to something more inline with it's true meaning....."Inflation Theory"???

    I used to have a hard time understanding the word "explosion" when used in the context of the Big Bang, but when the word "inflation" is used, it makes much more sense.

  17. #47
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    Quote Originally Posted by Xibalba View Post
    The fact is : particles involved in an explosion do not
    accelerate with time.
    Of course they do! In most explosions, anyway.
    Particles start out at rest relative to each other,
    then they are moving rapidly apart. Acceleration.

    Exceptions would be something like the geometrical
    uniform expansion Van Rijn suggested, shown in my
    animation, linked above. In that case the speed is
    uniform from the beginning. Real world cases would
    involve at least some accelerations.


    Quote Originally Posted by caveman1917 View Post
    If it was an explosion, you wouldn't expect the recessional
    velocity of a galaxy/piece of debris to speed up wrt you as
    it gets farther (just Hubble's distance-velocity formula, not
    talking about acceleration of the expansion).
    Sure I would! The farther apart two particles are in an
    explosion, generally the faster they are moving away
    from each other.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  18. #48
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    Quote Originally Posted by WayneFrancis View Post
    Quote Originally Posted by Jeff Root View Post
    The Big Bang sure looks exactly like an explosion to me.
    ...

    In every way, it resembles an explosion exactly.
    Problem #1. Explosions have a definable point in space/time
    where they begin. The big bang at best only has a definable
    point in time where it began as it happened at evry point in
    space as far as we can tell.
    I was not aware of any requirement that explosions must
    have "a definable point in space/time where they begin."
    I don't see any reason for such a requirement. I don't see
    that requirement ever being applied to other explosions.

    Did the Cambrian explosion have a definable point on the
    Earth where it began? None is known. I doubt there was
    such a point.

    Quote Originally Posted by WayneFrancis View Post
    Problem #2. Explosions do not seem to speed up, slow down
    then speed up again.
    They don't? Why not?

    Why shouldn't they?

    If you saw an explosion, then learned that it speeded up,
    slowed down, then speeded up again, would you change
    your mind about whether you had seen an explosion?

    Quote Originally Posted by WayneFrancis View Post
    The big bang and the expansion we see now seems to do
    just that.
    Yes. So?

    Quote Originally Posted by WayneFrancis View Post
    Problem #3. Explosions are not homogeneous. The big
    bang seems to be very homogeneous.
    Who says explosions are not homogeneous? What do
    you mean by the assertion? I'll grant you that the Big
    Bang appears to have been very homogeneous. So?

    If you saw an explosion, and then found out that it was
    very homogeneous, would you change your mind about
    whether you had seen an explosion?

    Quote Originally Posted by WayneFrancis View Post
    Probably more but "exactly" is a very strong word to use
    on an analogy and I'd have to disagree with you there.
    I don't think that calling the Big Bang an "explosion" is
    an analogy. It clearly was an explosion.

    Quote Originally Posted by WayneFrancis View Post
    Quote Originally Posted by Jeff Root View Post
    The words in the parenthesis don't add anything.
    We extrapolate backward in time. The farther back we
    extrapolate, the more compact was the part of the
    Universe we can see now. We can't extrapolate
    accurately all the way back to the very beginning, so
    the "finite" size you refer to is whatever size it was
    at any particular time.
    I think it is better said that our visible universe had a finite
    size at the start of the big bang. The universe could still be
    infinite.
    Whether the visible Universe had any size at all at the start
    of the Big Bang is unknown. Analysis using general relativity
    alone predicts a singularity at the beginning, at which the
    Universe (visible and invisible) had zero size, or no size.
    That conflicts with quantum mechanical predictions, though,
    so it is unlikely to be correct.

    Quote Originally Posted by WayneFrancis View Post
    Quote Originally Posted by Jeff Root View Post
    I don't think a singularity usually means a broken
    model. It just means a place where some value
    becomes zero, and as a result, other values become
    impossible to calculate.
    Doesn't a "undefined" answer = broken model? If you have
    a model that in one or more places does not give you an
    answer then wouldn't that be broken if you want an answer
    at those places?
    No. A classic example of a singularity is the latitude and
    longitude of the Earth's poles. The latitude is defined as
    90 degrees north or south, but the longitude is undefined.
    That is not a problem with the coordinate system. It is
    just an amusing fact about the coordinate system.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  19. #49
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    Quote Originally Posted by WayneFrancis View Post
    Quote Originally Posted by Jeff Root View Post
    Exactly the same as an explosion.

    The first part of that is exactly the same as an explosion.
    Gravity slows it down in all cases. In some cases, some
    of the bits escape and keep on going. In other cases,
    they don't.

    The second part-- All my books are from the 1980's or
    earlier. I have no idea what this "accelerating process"
    is that you refer to. I've never heard of it, since it
    wasn't discovered until 1998.
    ? So you have a problem that we didn't have good enough
    observations to tell that the expansion appears to be speeding
    up until 1998 and thus you can discount that so the big bang
    still appears "exactly" like an explosion to you?
    The fact that the expansion appears to currently be
    accelerating is irrelevant to the fact that the Big Bang,
    which occurred some 13.7 billion years ago, appears to
    have been an explosion. The mechanisms of the two
    may or may not be related, but even if they are one and
    the same, that fact has no bearing on the fact that the
    Big Bang appears to have been an explosion.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  20. #50
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    Quote Originally Posted by Jeff Root View Post
    Sure I would! The farther apart two particles are in an
    explosion, generally the faster they are moving away
    from each other.
    Use a very simple explosion, a gunshot. You're actually claiming that the bullet keeps increasing in speed the farther it gets from the gun?

  21. #51
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    Quote Originally Posted by speedfreek View Post
    We've been here before with Jeff.

    I think the sticking point here is the interpretation of distance in the distance-velocity formula. For sure, the higher the redshift, the faster the recession velocity. The higher the redshift, the earlier in the history of the universe we are seeing.

    A z=7 galaxy is seen as it was 13 billion years ago, receding really fast. A z=1.4 galaxy is seen as it was 9 billion years ago, receding at a slower rate. As redshift reduces, so does recessional velocity.

    Nowhere do we actually see something with greater proper distance actually receding faster than something with a lesser proper distance - the metric expansion is inferred, rather than observed. What we observe is that the longer the light has been travelling, the faster the object is receding. Objects in the early universe were receding faster than objects in the later universe...
    I'm not sure why you bring redshift into it? You're right that neither proper distance nor recessional velocity are directly observed, however the model is very clear on the relation between the two. A greater proper distance implies a greater recessional velocity. It gets a bit complicated for high redshifts since you have to calculate in a changing hubble constant over time, but the basic point doesn't change, greater proper distance is higher recessional velocity.

    This is probably why you bring up that objects in the early universe were receding faster than in the later universe, for the point under discussion that is actually incorrect. The correct statement is that the recessional velocity at a constant proper distance is falling over time. So if we draw a sphere of some constant radius around us, and check the velocity with which distant galaxies cross that sphere, that velocity will drop over time (decreasing hubble constant).

    However the point here is not to track a constant-radius sphere, but to track a single chosen galaxy. As this galaxy is increasing in proper distance wrt us, it is increasing in recessional velocity, even though the hubble constant is falling. This is akin to tracking a piece of debris in a normal explosion (like a bullet from a gun), which Jeff Root seems to think also increases in recessional speed over time as it gets farther away. The two have fundamentally different dynamics.

  22. #52
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    Jeff Root, an explosion is a rapid expansion of matter/energy into existing space. The BB is theorized to be the expansion of space itself at all points within existing space.

    You say the BB looks like an explosion. That would imply observing it from outside the expansion. One could not observe the BB from outside because there is no outside existing space so saying it "looks" like an explosion makes no sense.
    "There are powers in this universe beyond anything you know. There is much you have to learn. Go to your homes. Go and give thought to the mysteries of the universe. I will leave you now, in peace." --Galaxy Being

  23. #53
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    Jeff Root has been suspended for completely ignoring moderator advice about not hijacking this thread.

    I'm closing this thread while we think about what to do with it.
    At night the stars put on a show for free (Carole King)

    All moderation in purple - The rules

  24. #54
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    Xibalba,

    If it is OK with you, I'm going to reopen this thread, but move it to Astronomy, where the conversation can broaden beyond a simple Q&A format. If you have a problem with this (you are the OP) please Report this post and let us know your wishes.
    At night the stars put on a show for free (Carole King)

    All moderation in purple - The rules

  25. #55
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    In explosion, matter is given a push, and continues onward at same speed forever, only lessened by gravity.
    There's no necessary isotropic relation between distance and speed in the debris of an explosion.

    In big bang inflation, space is created between bits of matter, at something approaching a constant rate, everywhere. This ensures an isotropic distance/recession velocity equation, as is observed. Not explosion like, more similar to recession velocity of poppy seeds in a rising loaf of bread.

  26. #56
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    If considering an alternative to BB theory, one might see if there are unresolved issues that may be due to arbitrary a priori assumptions that prevent their resolution.

    A particular problem is the Cosmic Age Problem. It appears there are some quasars that are older than their surrounding space-time would admit. An early attempt to resolve the issue was to invoke a "tired light" hypothesis. However, only these particular examples would exhibit the "tired light" and it would not appear elsewhere where large mass concentrations would also occur which undermines the application of the "tired light" hypothesis as a general rule.

    An underlying assumption of BB theory is that of linear time as the 4th dimension in GR. If the first instance of time was linear then one has to consider the first instant as a condensed state. If time was non linear or symmetric prior to becoming linear then the universe may have been purely quantum mechanical on large scales as well as the very small. There would be a place for the older quasars that source the cosmic age problem.

    Interestingly, there would still have to be gravity to make the mass concentrations even though the symmetric time precedes the linear time of GR. So, rather than considereing gravity as being less than GR fundamental as considered by the recent entropic ideas favored by Verlinde, gravity would be actually more fundamental than GR. This is in the opposite direction of the entropic idea where the four dimensional (with linear time) GR is the midground.

    On the other hand. perhaps there will eventually be a resolution of the cosmic age problem within GR constraints.

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    Quote Originally Posted by RandyD123 View Post
    I wish the science community would have "coined" a different term than Big Bang. I wish the science community could change that term to something else. If we have now decided that Pluto is no longer a planet then we can surely change the name of Big Bang Theory to something more inline with it's true meaning....."Inflation Theory"???

    I used to have a hard time understanding the word "explosion" when used in the context of the Big Bang, but when the word "inflation" is used, it makes much more sense.
    Yes, the term explosion is inadequate, no matter what Jeff says, and I've put it between these : " " to let everyone know I am not really in favor of the term "explosion. If they do change the term for Inflation Theory, I think it'd be a great step forward for universal knowledge and against misinformation.

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    Quote Originally Posted by Swift View Post
    Xibalba,

    If it is OK with you, I'm going to reopen this thread, but move it to Astronomy, where the conversation can broaden beyond a simple Q&A format. If you have a problem with this (you are the OP) please Report this post and let us know your wishes.
    Thanks, sir. It is alright with me.

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    So... if space is expanding, doesn't it need energy to do so? and where does this energy come from?

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    Quote Originally Posted by Xibalba View Post
    Yes, the term explosion is inadequate, no matter what Jeff says, and I've put it between these : " " to let everyone know I am not really in favor of the term "explosion. If they do change the term for Inflation Theory, I think it'd be a great step forward for universal knowledge and against misinformation.
    The term is the Standard Cosmological Model or the Lambda Cold Dark Matter (ΛCDM) model. You do not see the term Big Bang in actual cosmology papers very much. The name Big Bang hangs around, mostly, due to it being more dramatic sounding for popular science writers and news reporters. News reporters don't know any better, but science writers should.

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