• Amalac
    309


    That is how I would define it, but I didn’t use “past” in my statement. You transcribed the term into it.Mww

    Then what did you mean when you said “there is no present”?

    So is this where you’re coming from? And by association, is this the hypothetical proposition the truth of which you find doubtful?Mww

    The hypotetical I'm refering to is “If the universe has an infinite past, then an infinite amount of time has elapsed up to the present”.

    You’re equating your “if the past were infinite” with his “an eternity must have elapsed”Mww

    No, I don't think those two mean the same thing, I'm saying: The past is infinite ≠ an infinite amount of time has elapsed, because to say that time has elapsed implies that it elapsed since some moment in time to some other moment in time, and hence the notion of time elapsing is not applicable to infinite amounts of time, but only to finite intervals of time.

    For example: 20 years have elapsed since I was born, up to the present. But you can't say: infinitely many years elapsed since ???, up to the present day.

    If one can't say since when the infinite amount of time elapsed, then I maintain that it couldn't have elapsed, but that a universe with an infinite past does not rest upon the supposition that an infinite amount of time has elapsed up to the present day.
  • Mww
    2.5k
    what I said was that he maintained that if the past were infinite then that implies that an infinite amount of time has elapsed.

    I'm not saying Kant maintained that the universe had an infinite past, I'm doubting the truth of that hypothetical proposition.
    Amalac

    The hypotetical I'm refering to is “If the universe has an infinite past, then an infinite amount of time has elapsed up to the present”.Amalac

    Man, this hypothetical’s got a farging mind of its own donnit? Seems “up to the present” makes an appearance in this current iteration, which changes the entire proposition.

    Anywhooo.....so you doubt the truth of the proposition that if the universe has an infinite past then an infinite amount of time has elapsed up to the present.
    ————-

    You’re equating your “if the past were infinite” with his “an eternity must have elapsed”
    — Mww

    No, I don't think those two mean the same thing,
    Amalac

    Neither do I. I was guessing you were equating them because that’s all I could find that was even close.
    ——————

    I'm saying: The past is infinite ≠ an infinite amount of time has elapsedAmalac

    I am vindicated!!!! No where in this: If the universe has an infinite past, then an infinite amount of time has elapsed up to the present, is to be found this: The past is infinite ≠ an infinite amount of time has elapsed. YEA!!!

    to say that time has elapsed implies that it elapsed since some moment in time to some other moment in timeAmalac

    OK.....

    hence the notion of time elapsing is not applicable to infinite amounts of time, but only to finite intervals of time.Amalac

    Hmmm......and what of the idea of a succession of a series of times that never completes? Isn’t a succession in a series of times the same as an elapse of time? A succession in a series makes no need of an amount for each time of the series. Even so, isn’t an infinite series of successive finite intervals of minutes, still an infinite amount of time?

    “....up to every given moment of time, an eternity must have elapsed, and therewith passed away an infinite series of successive conditions....”
  • Amalac
    309


    Man, this hypothetical’s got a farging mind of its own donnit? Seems “up to the present” makes an appearance in this current iteration, which changes the entire proposition.Mww

    Well, the first time I thought the “up to the present” part went without saying, but seeing how that lead to misunderstandings, you are right that I should have been more careful and should have stated it explicitly.

    The Popper quote in the OP does mention it though, so I thought the “up to the present” was implied:

    (...)Now, in his first proof, Kant simply argues that the world must have a beginning in time, since otherwise an infinite number of years would have elapsed at the present moment, which is impossible. This concludes the first proof. — Karl Popper

    Hmmm......and what of the idea of a succession of a series of times that never completes? Isn’t a succession in a series of times the same as an elapse of time?Mww

    I guess you meant to say “Isn't a succession in a series of time the same as a lapse of time?”

    A succession in a series makes no need of an amount for each time of the series.Mww

    Not quite sure what you mean by this, but if you mean that it doesn't need to have an interval with an infinite amount of time elapsing, then that is my point, since an interval must, by definition, have a beginning and an end, whereas a universe with an infinite past doesn't have a beginning, although it would have an end (the present moment/ the “now”). An interval of time must have both a beginning and an end in order for time to elapse in it.

    Even so, isn’t an infinite series of successive finite intervals of minutes, still an infinite amount of time?Mww

    In a universe with an infinite past, one could say that there would be infinitely many finite intervals of time, which, when added, make up an infinite amount of time.

    But if that's all that Kant meant when he said that:

    “....up to every given moment of time, an eternity must have elapsed, and therewith passed away an infinite series of successive conditions....”Mww

    ... then I don't see what the supposed contradiction is, he says (in my translation of the Critique):


    the infinity of a series consists in that it can never be finished by means of successive syntheses. — Kant

    To make things clearer: if we were talking about an infinite future, and modify what Kant says so as to apply to a universe with an infinite future, then we could interpret what Kant says in a way that makes sense: time could never, going forward in time, be “finished”, in a universe with an infinite future time. What would follow from that is: therefore, the infinite future temporal series of finite intervals can never be completed (forwards in time) since you will never arrive at a final interval of time, and therefore it would be contradictory to hold that in such a universe we could arrive at a final moment/interval of time in the timeline, since that would imply that it both can and cannot be completed.

    However, when saying that the infinity of a past temporal series consists in it never being finished/completed, what would be meant, it seems to me, is: If you start from the present moment/the “now”, and go backwards in time, then you will never arrive at a moment in time that is the beginning of time/ a first finite interval of time, therefore the infinite series of finite temporal intervals can never be completed (backwards in time).

    And so, if that is what is meant by “completed”, then there is no contradiction in holding that a universe with no beginning in time would not be completed backwards in time, but would be completed forwards in time, since it would be completed/finished by the “now”/ the present moment, in the same way in which the series of negative integers cannot be completed towards the left direction of the x axis if you start with any particular negative integer/ any particular interval between two integers, but can be completed towards the right direction of the x axis if you start with any particular negative integer/any particular interval between two integers, since it is “completed” by its last interval from -2 to -1.

    So, to make the mathematical analogy clear:

    -1= the present, the last element of the series, which finishes/completes it .

    The x axis in the cartesian plane, ending/ being completed with -1= the timeline of the universe.

    - infinity/ the three dots to the left of the timeline= The infinite past.

    The series of negative integers is “completed”, forwards from any particular negative integer/ interval (so to speak) between integers by its last interval from -2 to -1 (which represent the moment exactly one year before the present moment, and the present moment, if we use years as our units of time) ; but is not completed backwards from any particular negative integer.

    Hopefully now I made things clearer.
  • jorndoe
    1.2k
    On an infinite past, time is complete at any moment if complete means that nothing's missing.
    If complete means finite, then we've just shown what we assumed.

    It's not difficult to derive counterintuitives.
    Deriving a contradiction (p ∧ ¬p) is the task, though, at least it is if an infinite past is claimed impossible.
  • Bartricks
    3.3k
    I agree with Kant if the point is that there cannot be any actual infinities and thus there cannot be an infinity of past events.

    But I think there is no problem with an event becoming ever more past for infinity. For that's a potential infinity, not an actual one.

    The mistake most make when it comes to time is to conceive of it as a kind of extended stuff, and that immediately generates actual infinities. For now any region of time, like any region of space, can be infinitely divided. And thus we have to posit actual infinities. Which can't exist.

    One also gets other absurdities, such as a past-most event that nevertheless cannot become any more past (even though clearly all past events are getting more and more past all the time).

    Intuitively it seems like there is no limit to how past an event can become, and no limit to how far in the future an event can be. Time is boundless.

    What this teaches us is that time is not an extended substance. It's a category error to think of it that way.

    Another quite different way of thinking about time is to think of it as a set of attitudes. As an analogy, take hate. It is impossible to hate an infinite amount of things. But there is nothing impossible in one hating something more and more without limit. There seems no upper limit to how much one can hate something, yet we do not have thereby to suppose the existence of some kind of infinitely extended stuff - hate - that we acquire ever more of. It's just an attitude. And though attitudes cannot be divided, they can be of infinite potential intensity.

    Thus for an event to be past is for it be being 'past-ed' more and more intensely. In this way the first event or events can 'recede' forever into the past, for the past is no longer a strange endless zone, but an attitude that is growing in intensity.
  • Manuel
    984
    The statement that the universe cannot be infinite towards the past because that would imply going through or traversing an infinite number of events to get to the present seems false to me, since it seems to assume that in traveling such a series of events one goes through or traverses from an initial moment to the present, while this infinite universe towards the past by definition has no initial moment.

    If, on the contrary, the journey begins at some point in the past which is not an initial moment, it does not matter how much one goes back in the timeline, the events and time from that moment to the present will always be finite, and there is therefore no impossibility in a universe whose time is infinite to the past.
    Amalac

    I'm aware that you used Kant in the discussion. I'm more interested in the thought experiment itself of time going "back" infinitely. It's been in the back of my mind recently and I was going to start a thread on the topic, but then saw this one.

    Maybe this is cheating and is probably also quite ignorant but I'd like to put aside what physics says and just take the topic as is, meaning, if time is infinite and had no beginning, how could we be here?

    Let's me take a stab at your argument, for my own benefit. As I understand what you're saying: even if time had no beginning it would not matter because we are finite, so we can place ourselves anywhere on the timeline and no be bothered about how we got here.

    Isn't the counterargument here that in order to get to now, we had to begin somewhere. But if time is infinite, how could we place ourselves here? An infinite amount of time has gone on before we got here.

    Either a part of infinity is finite or if not, it is also infinite. If a part of infinity is also infinite, regardless of not having starting conditions, we could not be here.

    But this raises more problems, if a part of infinity is finite, wouldn't we have to go through an infinite amount of time to reach a portion of infinity which is not. How's that possible?

    Unless I'm stuck with a linear idea of infinity.. Sorry for the length, but I'm curious about a reply. It's likely muddled thinking on my part.
  • Amalac
    309


    Let's me take a stab at your argument, for my own benefit. As I understand what you're saying: even if time had no beginning it would not matter because we are finite, so we can place ourselves anywhere on the timeline and no be bothered about how we got here.Manuel

    Well, my view is not that we don't need to be bothered about how we got to the present, but rather that we should not (and need not) say things like “an infinite amount of time has elapsed up to the present” when we examine the consequences of assuming that the universe had no beginning in time, we should only talk about time elapsing when talking about particular intervals of time. In fact, the very notion of time "elapsing" implies a beginning and an end of an interval in which it elapses (most definitions of the word I have seen do assume that, anyway).

    If the word “elapsed” does not imply a “since X point in time to Y point in time”, then it means something different from what it means in a statement such as: “5 years have elapsed since my birthday 5 years ago up to now”, since otherwise necessarily one must be able to answer the question: “infinitely many years have elapsed since (when?) up to now”.

    Isn't the counterargument here that in order to get to now, we had to begin somewhere.Manuel

    Why is it that we had to begin somewhere?
    Doesn't that beg the question by already assuming that there must have been a beginning in time?

    But if time is infinite, how could we place ourselves here? An infinite amount of time has gone on before we got here.Manuel

    If by “an infinite amount of time has gone on before we got here” you mean “ if the universe had no beginning in time, then an infinite amount of time would have elapsed before we got here”, then I have already said why I think that's not the case. Time can only elapse since some moment to some other moment. It is clear, therefore, that the idea of time elapsing only applies to finite intervals of time.

    Kant therefore can't use the idea that if the universe had no beginning in time then that logically entails that an infinite amount of time would have elapsed, to show that a universe with no beginning in time would imply a contradiction, since such a universe doesn't logically entail what he says it entails.

    Such is my current view on the matter anyway.

    Either a part of infinity is finite or if not, it is also infinite. If a part of infinity is also infinite, regardless of not having starting conditions, we could not be here.Manuel

    A part of “infinity” can be infinite, yes. In the set of all positive integers, the set of all even numbers which is part of the set of all positive integers is also infinite. But of course a part of infinity could also be finite, for instance the set of all integers bigger than 0 and smaller than 5, which is also part of the set of all positive integers.

    So, when talking about the timeline of the universe, which part of it are you saying would be infinite, and how would that imply that “we could not be here”?

    But this raises more problems, if a part of infinity is finite, wouldn't we have to go through an infinite amount of time to reach a portion of infinity which is not. How's that possible?Manuel

    Again, when saying we would have to “go through an infinite amount of time”, you must specify since when we would supposedly have to “go through” an infinite amount of time, since in the very definition of time elapsing, a beginning and an end of the lapse of time are pressupposed.

    So no: if the universe had no beginning in time, it's not the case that that would necessarily entail that we would have to go through an infinite amount of time to get anywhere.
  • jgill
    1.3k
    It may be possible that there was an initial moment and yet time extends infinitely into the past. Think time dilation and the Big Bang. Just ruminating, pay no mind.
  • Manuel
    984
    So, when talking about the timeline of the universe, which part of it are you saying would be infinite, and how would that imply that “we could not be here”?Amalac

    I'm not sure I follow completely, I may be, but I may not be. I think that part of the problem may be that there's our innate conceptions of space and time, or spacetime if we are to incorporate modern physics and spacetime outside our conception of it.

    This may be the wrong way to state this...

    I think that by now, we should try to distinguish our conceptions of spacetime with spacetime in the universe. Absent human beings, strictly speaking, yes, we can't speak of time "elapsing" or as I prefer to say "passing", as these terms must imply our conceptions of them.

    But if there is spacetime outside our conceptions of it, as appears to be the case then I think that in order to speak at all, we are forced to use our human vocabulary. Perhaps we can speak of one infinite span of time, or an infinite number of events, this would go on "backwards" forever.

    The time in the universe, on this thought experiment, goes back forever. If it does, how can we get to any point at all, given that an infinite time preceded our species?

    Why is it that we had to begin somewhere?
    Doesn't that beg the question by already assuming that there must have been a beginning in time?
    Amalac

    We as a species evolved at some point in evolutionary history. It's from that perspective that we began as a species. It does not presuppose a beginning of time in the universe, but it does presuppose a beginning of time as we conceive it. In that respect I'd stick my neck out and say that we "began" once we had our conception of time.

    since in the very definition of time elapsing, a beginning and an end of the lapse of time are pressupposed.Amalac

    In our conception of time yes. I think it differs in the external world.

    But I could be way off. Again, just throwing out ideas.
  • Manuel
    984
    It may be possible that there was an initial moment and yet time extends infinitely into the past. Think time dilation and the Big Bang. Just ruminating, pay no mind.jgill

    If the Big Bang is true and complete, how can we speak of time before that? It would be analogous to saying what's a feature of Earth that is higher than Everest.

    What did you have in mind with time dilation?
  • Mww
    2.5k
    Take care. Lot’s of edits here. Depending on when your response begins, in relation to my final edit.

    Ever onward......

    In a universe with an infinite past, one could say that there would be infinitely many finite intervals of time, which, when added, make up an infinite amount of time.

    But if that's all that Kant meant when he said that:

    “....up to every given moment of time, an eternity must have elapsed, and therewith passed away an infinite series of successive conditions....”
    — Mww

    ... then I don't see what the supposed contradiction is, he says (in my translation of the Critique):

    the infinity of a series consists in that it can never be finished by means of successive syntheses.
    — Kant
    Amalac

    Kant is working onward, you are working backward. Referencing your universe with “past” presupposes a regression in time from some other given time, otherwise “past” is irrelevant. His “up to every given moment” presupposes a progression in time from every other time, so it makes no difference what that some other time is. They are indistinguishable. Kant is working with time alone, you are working with something existing in time.

    The contradiction resides in your inclusion of the universe as an uncompleted series. If it was, then the elapsed time of the universe, your “infinitely many finite intervals of time” for the universe is impossible, therefore there could be no universe, a contradiction. The universe would never be “finished by means of successive synthesis”, from which follows necessarily that talk of “in a universe with an infinite past”, is meaningless. Even if you think the universe the same as Kant thinks the world, it is still to be treated an a completed series of times, from which there arises a present condition of that which is called “universe”.
    ————-

    in the same way in which the series of negative integersAmalac

    The set of negative integers is an uncompleted series, in which the last member is impossible to represent. Even so, the conception of integers remains. In the case of the universe, given its existence, which is the equivalent of zero for the reference of infinite negative integers, it is merely the infinite set of constituents of the universe that cannot be represented, while the conception of the universe itself remains. This shows the compatibility of arguments with respect to integers, with arguments with respect to the infinite series of times for an existent whole.

    Nevertheless, while it is possible to think the infinite past of the universe in which it has no beginning, such thought is necessarily contradicted by experience. It is at the same time possible to think the infinite series of negative integers, and forever be safe from contradiction by experience. So the arguments are not compatible.

    Hence.....the conflicts of pure reason, the antinomies.
    —————

    Hmmm......and what of the idea of a succession of a series of times that never completes? Isn’t a succession in a series of times the same as an elapse of time?
    — Mww

    I guess you meant to say “Isn't a succession in a series of time the same as a lapse of time?”
    Amalac

    No, I said what I meant to say. Time can contain nothing but intervals of itself. Things are in time, but time is not in the things. Ultra-modernists posit time as a property, such that time can be in things, but then they cannot explain how empirical things can have an infinite property.
    ————-

    So, to make the mathematical analogy clear:Amalac

    It is clear, but I don’t think it sufficient to support the OP, which asks “can the universe be infinite towards the past”, and, of course, has nothing whatsoever to do with the antinomies.

    Metaphysics.....the most fun to be had without paying for it.
  • Amalac
    309


    The contradiction resides in your inclusion of the universe as an uncompleted series. If it was, then the elapsed time of the universe, your “infinitely many finite intervals of time” for the universe is impossibleMww

    And why would there being infinitely many finite intervals of time be impossible given a universe with no beginning in time/ infinite past, exactly?

    Like I said, those infinitely many intervals (or “syntheses”) go backwards in time since the “now”, or since any other particular moment in time before “now”, so the only thing those intervals make impossible is for there to be a beginning moment which completed the series backwards, which is what is entailed by the definition of a universe with no beginning in time, they don't render the series being completed forwards by the “now” impossible.

    The universe would never be “finished by means of successive synthesis”, from which follows necessarily that talk of “in a universe with an infinite past”, is meaningless.Mww

    I'm not sure how that follows:

    1.In a universe with no beginning in time, there would be infinitely many finite intervals of time.

    2. Those intervals or synthesis could never end (backwards in time)

    3. Therefore, given that 2 is true, a universe with no beginning in time would not have a present moment, a “now” which completed the series (forwards in time).

    4. The actual universe does have a present moment which completes its temporal series (forwards in time).

    5. Therefore, the talk of “in a universe with an infinite past..." is meaningless.

    The jump from step 2 to step 3 is what seems like a non-sequitur to me. That, or equivocation of the idea of a series being “completed”, which can have 2 different meanings.

    When the natural thing to infer would be rather:

    1.In a universe with no beginning in time, there would be infinitely many finite intervals of time.

    2. Those intervals or syntheses could never end/ be finished (backwards in time)

    3. Therefore, a universe with no beginning in time would not have a beginning in time, since that
    would imply that the temporal series would be
    completed (backwards in time), which necessarily can't be the case given 2.

    And yes, that's just how a universe with no beginning in time/ infinite past is defined, 3 is an analytic truth and therefore contains no contradiction.

    While it may not be contradictory to speak of a universe with an infinite past, given the existence of it, it is still contradictory to speak of a universe with an infinite elapsed time, which makes no reference to any given time.Mww

    Again, if by “infinite elapsed time” we mean that in such a universe there would be infinitely many finite intervals/syntheses of time, then I don't see why its contradictory with the premise of a universe with an infinite time, for the reasons given before.

    The set of negative integers is an uncompleted series, in which the last member is impossible to represent.Mww

    If you sort the series in descending order, then there is no last member indeed.

    But if you sort the series in ascending order, then its last member can be represented, its -1.

    I'm refering to that series sorted in ascending order, and in that series the correct statement would be: “The set of negative integers is an uncompleted series, in which the first member is impossible to represent”.

    In that case, the series of negative integers would be an uncompleted series descendingly since it has no first term, but not ascendingly since it has a last term (-1).

    All in all, I just don't see how Kant's argument is that much different from the argument of the first cause of, say, Aquinas, if one just replaces “causes” with “syntheses” ( I mean besides the fact that Kant does not continue to deduce the existence of God from that beginning in time he got from this thesis, which is understandable given that the antithesis can be “proven” as well).

    (...)take again the arguments (of Aquinas) professing to prove the existence of God. All of these, except the one from teleology in lifeless things, depend upon the supposed impossibility of a series having no first term. Every mathematician knows that there is no such impossibility; the series of negative integers ending with minus one is an instance to the contrary. — Bertrand Russell

    So if one argues that Kant's argument “proved” that the temporal series of the universe must have had a beginning in time, by the same reasoning one could also prove that the series of negative integers must have a first term, a smallest negative integer, since otherwise the series could not end with -1, which is clearly not the case.

    No, I said what I meant to say.Mww

    Sorry, that was a typo, I meant to write “a succesion in a series of times” with “times” in plural, what I was trying to ask was if by “an elapse of time” you meant to say “a lapse of time”.

    Metaphysics.....the most fun to be had without paying for it.Mww

    Well, I hope you are at least having some fun, and not losing your patience despite my obstinance in trying to understand Kant's argument (if indeed I misunderstood him and am just hopelessly confused).
  • Mww
    2.5k
    So if one argues that Kant's argument “proved” that the temporal series of the universe must have had a beginning in time, by the same reasoning one could also prove that the series of negative integers must have a first term, a smallest negative integer, since otherwise the series could not end with -1, which is clearly not the case.Amalac

    Again....forward vs backward. The infinite series of negative integers doesn’t end with -1, it begins with it. The smallest negative integer is -1, in that it is the least distant from its referent. The universe, conversely, is the absolute furthest from its referent, which is its non-existence, made explicit by the consideration of its infinite past.
    ———-

    And why would there being infinitely many finite intervals of time be impossible given a universe with no beginning in time/ infinite past, exactly?Amalac

    That there are an infinite amount of intervals of time of the universe is not contradictory, for any given whole is infinitely divisible, and the universe is itself a given whole. But how can there even be a universe with no beginning in time?

    No beginning in time does not carry the same implications as an infinite past of time. Past implies backward from original present, so an infinite past just means backwards indefinitely from the present. In both of these, the present is given. But for a universe with no beginning, there cannot be a given present, hence the absurdities in connecting a non-existent, re: the universe, insofar as that which does not begin does not exist, with its past, infinite or otherwise.

    To think the infinite intervals of times of the universe, does not contradict itself. To think the infinite past of the universe, from its present, does not contradict itself, but experience does show its contradiction in fact. To think the universe as having no beginning contradicts everything about the universe. To say there is an infinite time lapse before the beginning of the universe just makes the universe impossible.

    Infinite time, in itself, and the universe, by itself, are incompatible. Metaphysically, this is a legitimate thesis if time is only a condition of all things and the universe is a thing. Or, it is equally legitimate if time is meaningless unless it relates things, and the universe is a thing.
  • jgill
    1.3k
    If the Big Bang is true and complete, how can we speak of time before that?Manuel

    You probably can't. The question then becomes, Is it possible that time evolved in a way that conflicts with current analysis and provides a path back in time that is unbounded, even to the moment of the BB?

    I know, sounds absurd. But I have been looking at a dynamical system in C in which, starting at a particular past moment, one analyzes a sequence that begins at n and devolves to 1, then begin at a larger n at the same starting point, etc.

    Just musing.
  • SolarWind
    88
    The mistake most make when it comes to time is to conceive of it as a kind of extended stuff, and that immediately generates actual infinities. For now any region of time, like any region of space, can be infinitely divided. And thus we have to posit actual infinities. Which can't exist.Bartricks

    I would actually phrase it a little differently. For me, time is the display of an imaginary clock. After all, it is not possible to place a clock inside the sun. Would someone claim in the inside of the sun there would be therefore no time?

    One must distinguish simply between events and the time itself. The events play no role for the abstract time, also not the Big Bang. I can imagine a clock, which survives all events and therefore this clock can indicate any time (it would have to be able to indicate however arbitrarily many digits).

    This clock could have shown any time back to negative infinity.
  • tim wood
    7k
    If the Big Bang is true and complete, how can we speak of time before that?
    — Manuel
    You probably can't.
    jgill

    Hawking's informal development comparing time to the surface of a sphere. Unbounded, unending.
  • Manuel
    984


    And others like Smolin say time is emergent.

    If Smolin is correct, it's very hard - if even possible - to think of anything "before" the emergence of time. But one must assume that there wasn't nothing in the sense of absolutely nothing: no energy, no quantum vacuum, etc, prior to the emergence of time.

    But if Hawking is correct, then at least time "remains". Though it's very hard to make any sense of any of this.
  • tim wood
    7k
    Probably useful to note there is no such thing as time in the universe. There is, on the other hand, how we look at it and attempt to understand.
    Though it's very hard to make any sense of any of thisManuel
    Amen!
  • Manuel
    984
    Probably useful to note there is no such thing as time in the universe. There is, on the other hand, how we look at it and attempt to understand.tim wood

    Sure. Just trying to use words to try and make some minimal sense of the things "out there", well aware of the myriad of complications attached to doing this.
  • Bartricks
    3.3k
    That's a metaphor. You think of it as a stuff, right? And that generates actual infinities. And that should tell you that that's the wrong way to conceptualize it.
  • Zelebg
    626
    That present point in time can not exist with infinite past seems the same as saying that some spatial point A can not exist on an infinite line, but I think I can prove that it actually can, here:

    ∞ <--------------A-------------> ∞
  • Mww
    2.5k


    That’s not an infinite line.

    You must have known that, so what did you think you actually proved?
  • Pfhorrest
    4.5k
    I have nothing of use to add to this conversation other than that you sound completely correct in your OP, and Kant (via Popper) is wrong.

    ETA: Maybe this could be useful: Kant’s problem is thinking of time the way flat-Earthers think of space. What is the Earth resting on? What is that resting on in turn? And that? Do we need a stack of turtles “all the way down”? Or is it instead a misapprehension of space to think that something can’t just be here, and there’s infinite room to look further down as far as we want, with no need for a stack of things “from the bottom” to hold “here” up.
  • Pfhorrest
    4.5k
    If the Big Bang is true and complete, how can we speak of time before that?Manuel

    In contemporary physics, the Big Bang is understood not as the total beginning of everything, but as the end of the inflationary epoch... which may have been going on for infinite time beforehand (or may not have, there’s no scientific evidence either way as of yet). But at some point (according to the latest models) the universe was mostly empty space expanding absurdly fast, we don’t know for how long, and then suddenly it stopped (at least in the part we can see) and all that expansion energy got dumped into all of the other fields, exciting them immensely, leaving an absurdly hot and dense (patch of the) universe, still expanding but less rapidly. That transition is what we now think of as the Big Bang.
  • Manuel
    984


    Thanks for the info, some clarification:

    So empty space contracted into the big bang?

    Is this connected to some of these cyclic big bang theories in which it is postulated that the universe expands and contracts many times?

    As I understood it, and apologies if I state it incorrectly, the Big Bang was a moment in which everything in the universe was compacted in a very small point of very high energy.

    "Before" that moment, there either was nothing or it's part of a cycle.
  • Manuel
    984


    Sorry if this question sounds stupid, but when it comes to math, I'm really mentally challenged.

    This type of system you are describing, it's a kind of recursive system or a "loopy" system, but it has a "starting point". Is this roughly what you have in mind?
  • jgill
    1.3k
    It's a dynamical system in C that is observed in the computation of an analytic continued fraction when evaluated by backward recursion:


    In this instance where . If it has a bearing here or for time dilation at the event horizon of a black hole is problematic. :chin:
  • Manuel
    984


    :scream:

    That's brutal.

    But I saw the word "recursion".
  • Pfhorrest
    4.5k
    Not so much contracted, but slowed. All we know (or posit in our current best theories) is that around 14 billion years ago the universe was much smaller and so very dense and very hot, and for an unknown, possibly infinite amount of time before that, it was mostly empty but expanding much more rapidly. The energy of the hotness is thought to have been converted from the energy of the expansion.

    Imagine an infinite grid that you’re zooming out from, and that gives you a picture of what rewinding time looks like: you never run out of grid to zoom out from, even when the “whole screen” has been zoomed down to a single pixel; and when you cross that point, it all starts zooming out even faster.

    We posit that inflationary (rapidly-expanding) period before the “hot Big Bang” to explain some observations about the early state of the universe, but we have no evidence suggesting anything about how long it had been going on beforehand.

    The theory of eternal inflation posits that that breakneck rapid expansion of mostly empty space is actually the normal state of the infinite (in size) and eternal (without beginning or end) universe, and the part of that universe we can see is just a (part of a) comparatively tiny part that randomly and temporarily slowed down; and the current acceleration of the expansion of space is the process of our part gradually returning to that normal state of absurdly fast expansion.

    If that theory is true, there are constantly “big bangs” going off all across the infinite universe, but they’re all so far apart and being accelerated away from each other so rapidly that none of them will ever have any chance of seeing each other, and the space between them is still mostly empty. So on a large enough scale view, whole lifetimes of “universes” like ours are just sparkling briefly all over space and time forever and always, and there always have been.

    And if that is the case, then if you look far enough back in time — really incomprehensibly far — whatever tiny speck of space expanded into the universe as we know it was at one point a tiny empty part of some other “universe”, which in turn began as an empty speck that some time incomprehensibly further in its past had been a tiny empty part of an even earlier “universe”, etc. And the empty space that will someday be all that’s left of the universe as we know it will be littered with uncountably many empty specks of space that will, incomprehensibly far in the future, each become a “universe” like ours themselves.
  • Manuel
    984


    Very interesting and many thanks for the detail and the visualization aspect, helps a bunch. I recall reading some of this in Hand's Cosmosapiens, but you're wording of it makes it "easy" to picture.

    The thing is, if this is true, it looks to me as we're just pushing back the origins question. That is, we have no possible conception as to why any universe began, or if it even makes sense to think so far back to a "first universe" - if it ever existed. But, if the theory is true - which I think it's safe to assume we just don't know - then too bad for our comprehension. It looks to me like Many Worlds on steroids, which would have to be accepted as fact.

    I suppose one question that lurks here, which philosophers could comment on a bit, is the idea of causality. I tend to like Galen Strawson's view on this, in which he rejects the regularity theory of causation: that things just happen, for no reason.

    I know "reason" is a loaded word, but what he has in mind is, there should be a regularity or a habit for which things happen as they do and not some other way. If there are no "reasons" why, then why have any laws at all? We could say that the next universe over is just a lump of green clay. If things just happen nothing is prevented, I guess. Obviously I'm speaking crazy here, but why does the universe(s) behave in this way?

    It's really mind-boggling. I mean, we already have more than enough figuring out stuff here on this tiny planet, to think that there are many universes, well damn. Fascinating.
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