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Space Science

How Deep Does the Multiverse Go? 202

Posted by samzenpus from the beyond-the-beyond dept.
StartsWithABang writes Our observable Universe is a pretty impressive entity: extending 46 billion light-years in all directions, filled with hundreds of billions of galaxies and having been around for nearly 14 billion years since the Big Bang. But what lies beyond it? Sure, there's probably more Universe just like ours that's unobservable, but what about the multiverse? Finally, a treatment that delineates the difference between the ideas that are thrown around and explains what's accepted as valid, what's treated as speculative, and what's completely unrelated to anything that could conceivably ever be observed from within our Universe.
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How Deep Does the Multiverse Go? More

How Deep Does the Multiverse Go?

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  • It's turtles all the way down (Score:5, Interesting)

    by Anonymous Coward on Sunday July 13, 2014 @02:02PM (#47443907)

    It's turtles all the way down.

  • Many worlds (Score:5, Funny)

    by Livius ( 318358 ) on Sunday July 13, 2014 @02:03PM (#47443913)

    In one version of reality, this is a first post!

    • That depends on your concept of identity across worlds. Surely the first post in another multiverse cannot be entirely identical to one in this one, as it exists in a different multiverse, not this one. Furthermore, it also differs from "this" post in that it is first in reply to the article posted on Slashdot*, or /.*. It also differs in that it wasn't made by you, but you*, who further differs from you in such a way that allows him to make that first post where you failed. If you're already so different f

  • Math? (Score:5, Insightful)

    by meerling ( 1487879 ) on Sunday July 13, 2014 @02:08PM (#47443943)
    "Our observable Universe is a pretty impressive entity: extending 46 billion light-years in all directions, filled with hundreds of billions of galaxies and having been around for nearly 14 billion years since the Big Bang."

    The observable universe is observable because there has been time for the light to travel that far, which can not exceed the age of the universe. Therefor, if the universe is 14 billion years old, then the furthest we could see in any direction is only 14 billion light years, giving a maximum, diameter of 28 billion light years.
    So why does the summary say it's 46 billion L.Y. across and only 14 billion Y. old?

    • Re:Math? (Score:4, Insightful)

      by ledow ( 319597 ) on Sunday July 13, 2014 @02:11PM (#47443973) Homepage

      If you assume a static, never-changing, fixed space... you might have been right.

      Isn't this how we know it's expanding?

    • Re: (Score:3)

      by MRe_nl ( 306212 )

      Special relativity
      http://en.wikipedia.org/wiki/S... [wikipedia.org]

      • Does that cover speed as well? 23 Billion Light Year radius and 14 Billion years old implies stuff is/was travelling at 1.6c. And if 46Billion LY was the radius, average speed becomes 3.2c.

        • Re:Math? (Score:5, Informative)

          by wierd_w ( 1375923 ) on Sunday July 13, 2014 @02:54PM (#47444221)

          Given a sufficiently large distance between two discrete points in the universe, the rate of hubble expansion between those points can exceed C.

          http://www.universetoday.com/1... [universetoday.com]

          You can think of it this way:

          You have a ruler-- You can only move along the ruler at at most, 100 units per second. (we will use this as an analogue for going C) However, for every second, for every 1000 units distance on the ruler, a new unit of distance magically appears. If you have a distance between 2 points that is sufficiently large, (In this case, in excess of 1,000,000 units) more than 100 units will be introduced every second, which is faster than your maximum rate of traversal-- So you will NEVER reach the target-- it receedes faster than you can get to it.

          http://www.universetoday.com/1... [universetoday.com]

          • It is just like when you start chasing a girl but never catch her because she keeps running away.

            Just be careful, sometimes but only very rarely, do they suddenly turn around and catch you. That is how I ended up married.

    • Re:Math? (Score:5, Informative)

      by NEDHead ( 1651195 ) on Sunday July 13, 2014 @02:13PM (#47443991)

      Because the expansion of space is independent of the light traveling through it, and the light that has just arrived came to us in some cased from objects that are now much further away than 14B lightyears

      • That would be cases, not cased. My Apologies

      • Because the expansion of space is independent of the light traveling through it

        nonsense statement...had to read twice to be sure, but this is just technobabble and not based on scientific definitions of "space" and "light"

        and the light that has just arrived came to us in some cased from objects that are now much further away than 14B lightyears

        if I understand you correctly, you're wrong...the whole point of GP, one which I think you're attempting to address, is that the only reason we know the universe's s

        • Re:not true, IIRC (Score:4, Informative)

          by wonkey_monkey ( 2592601 ) on Sunday July 13, 2014 @04:30PM (#47444749) Homepage

          nonsense statement...had to read twice to be sure, but this is just technobabble and not based on scientific definitions of "space" and "light"

          That's weird, I understood it perfectly as an (admittedly somewhat simplified) explanation of how space expands and how light travels through that expanding space. Don't blame your lack of understanding on what you imagine to be the GP's lack of clarity.

          in other words, **NO** there is not 'light' hitting us from 14B ly+

          No-one said there is. There is light hitting us which was emitted by objects which are now* more than 14 billion light years away.

          *for a given value of "now," that is, but I'm not sure I'd enjoy trying to explain that to you.

          • it's not that you don't *want* to explain, or that you think i wont' understand...no...

            you can't explain it

            you actually don't understand it yourself and are BS'ing

            i did make a coherent point, referencing the two main things we have that give us the age of the universe now

            > Cosmic Microwave Background

            > Gamma Ray Bursts

            There are others, but any new distant event is usually first compared to the two things listed above

        • Let me put it in terms you can understand: If you hold a rubber band with one end in each hand, and put an ant on the rubber band at one end headed toward the other, and the ant moves at a constant rate toward your other hand, and as the ant moves you stretch the rubber band, then your hands will be further apart than the ant has moved when the ant reaches your other hand.

          If you have a favorite animal, I can rephrase to accommodate.

          • If you have a favorite animal, I can rephrase to accommodate.

            Probably wouldn't work with my dog, it would just eat the rubber band.

          • your analogy, which i read elsewhere on this thread, is incorrect

            **we don't know** the nature of 'space' and the 'universe' like you're making out

            'space' is not like a rubberband and 'light' is not analogous to an ant crawling on said rubber band...it's just a bad analogy that doesn't prove anything either way

            just confuses things

    • The universe is expanding like others said... but it's still an incorrect statement. All of our measurements so far suggest that the universe is flat, and extends in all directions infinitely. It has no size, it's unending. Even more mind boggling is that if the many worlds theory is true, then there are also an infinite number of other universe that are equally as vast. Long story short? There really are Ewoks somewhere.

      • The universe is expanding like others said... but it's still an incorrect statement.

        The statement did say "observable universe."

        • "Universe" = everything.
          "universe" = everything observable.

          But that grammatical rule breaks down if you put the word at the start of a sentence.

          • Re: (Score:2)

            by pla ( 258480 )
            "Universe" = everything. "universe" = everything observable.

            Fan of Bucky, eh? :)

    • The observable universe is observable because there has been time for the light to travel that far, which can not exceed the age of the universe. Therefor, if the universe is 14 billion years old, then the furthest we could see in any direction is only 14 billion light years, giving a maximum, diameter of 28 billion light years.
      So why does the summary say it's 46 billion L.Y. across and only 14 billion Y. old?

      The universe is expanding all while light is in transit to our bug-eyed telescopes.

      For details: http://arxiv.org/pdf/astro-ph/... [arxiv.org]

    • Yeah, confused the hell out of me too the first time I heard it back in the 80's. If you search the "starts with a bang" website you'll find a well written article that explains why. Oh and 46 is the radius from our POV, so it's actually 92 "across".
    • Because they *were* 14 billion light years away, and are now probably 46...

  • I was getting used to the notions of multiverse so broad there exists a copy of me somewhere with a penis in place of the nose and a nose in place of the penis. And that's far from the weirdest things out there.

  • Brian Green;'s multiverse book (Score:3)

    by peter303 ( 12292 ) on Sunday July 13, 2014 @02:52PM (#47444213)
    Some of the the mind blowing chapters consider an infinite universe in space and time. Our local area could exactly repeat on the average of 10^150 light years, Brian calculates. And there could many more variants than exact repeats.

    Imagine an infinite number of exct copies of yourself, each sparated by immense distances. Image even more variants of yourslef, living slightly to greatly different lives.

  • Consider the time axis, from minus infinity to plus infinity.
    Somewhere along this axis the universe comes into existence.
    Call this point t0.

    Now why is t0 exactly t0? Shouldn't there be another universe, exactly equal to this one, with time t1 (!= t0).

    Now even if time is created as part of a "big bang", there should be a "meta-time" for which this holds.

    • Re: (Score:2)

      by RussR42 ( 779993 )
      Time is a measure of change. Until something changy exists, even if there was some kind of "meta-time", it would be meaningless. So meaningless that positing it's existence is pointless...

    • Consider the time axis, from minus infinity to plus infinity.
      Somewhere along this axis the universe comes into existence.
      Call this point t0.

      Now why is t0 exactly t0? Shouldn't there be another universe, exactly equal to this one, with time t1 (!= t0).

      Now even if time is created as part of a "big bang", there should be a "meta-time" for which this holds.

      No. Time is a part of this universe. There is no "meta" time, other universes do not necessarily have time. There is no t Minus infinity. We know exactly when time started (ok, to within a few trillionths of a second) You can no more go back further in time than that, than you can make a square circle.

      It's something that's hard to talk about because our language is so wrapped up in the idea that time is endless, but it's not.

      • Re:Please explain (Score:5, Insightful)

        by pla ( 258480 ) on Sunday July 13, 2014 @06:40PM (#47445333) Journal
        No. Time is a part of this universe. There is no "meta" time, other universes do not necessarily have time. There is no t Minus infinity. We know exactly when time started (ok, to within a few trillionths of a second).

        FTA: "The most amazing thing about it, though, is that this is exactly what the Universe was doing before the Big Bang, only with a much greater energy and at a much faster rate! This was the period known as Cosmic Inflation."

        Words like "before" presuppose the existence of time. If, as you postulate, time exists only as a function if this universe, then you have just established the de facto existence of "meta time" (at least if you believe TFA).
        • Good point! It is my understanding that modern science does not claim knowledge of any events prior to the big bang, nor does it claim that such a region of spacetime (or meta-spacetime, or whatever) exists at all. My understanding certainly could be wrong, but if not, it seems to simply suggest that the author of the article doesn't really know what he's talking about.

          • Re: (Score:2)

            by pla ( 258480 )
            True - I honestly don't have the background to evaluate whether or not TFA has that part correct, but have to give him the benefit of the doubt. :)

  • Especially liked raised BS flag on many worlds interpretation crackpottery.

  • As humans, we can't conceive of what's beyond, simply because we lack the mental capacity. Much like an amoeba is unaware of high interest rates.

    • Stating that something must lay beyond the "edge" of the universe, as the submitter does, basically means the person doesn't really understand basic cosmology.

  • Speculative. (Score:5, Insightful)

    by Oligonicella ( 659917 ) on Sunday July 13, 2014 @03:54PM (#47444575)

    Anything dealing with multiverse is speculative. Math does not constitute evidence.

    • And since it is outside our observable natural world, it is by definition super-natural.

    • Anything dealing with multiverse is speculative. Math does not constitute evidence.

      By that argument, everything we know about stars, quasars, black holes, and virtually everything else that isn't on our planet and relatively close to the surface is all speculative, too. Nearly everything we know about the stuff not immediately at hand is based on mathematical models, calibrated against "observations" which are often very, very indirect and themselves dependent on many layers of mathematical models derived the same way.

      I don't know enough about QM and many worlds theories to know how muc

  • This is just one person's (Score:5, Informative)

    by Bob Hearn ( 61879 ) on Sunday July 13, 2014 @04:11PM (#47444667) Homepage
    personal opinion of the status of the various ideas labelled "multiverse", inappropriately presented as fact. There is certainly not a consensus view that these opinions are correct, as you might mistakenly infer. In fact, "..., with different Big Bangs but very likely with the same fundamental laws and constants" -- it seems to me the weight of professional opinion is actually more on the other side here. His views on Everett's many-worlds interpretation are also counter to those of most people who accept it as valid in the first place. Perhaps most egregiously, if he is going to borrow (linking to) Tegmark's categorization of the different levels of multiverse, he should at least get them right. But he refers to Tegmark's level 1 as level 0, level 2 as level 1, and is a little confused about the distinction between 1 and 2. If you want a much more thorough, and objective, discussion of the various multiverse ideas, you want to read Brian Greene's The Hidden Reality. And of course Tegmark's Our Mathematical Universe is the latest entry into this field, a manifesto of sorts.

  • Sure, there's probably more Universe just like ours that's unobservable,

    This has come up before, and I ended up in an extended conversation with someone who was absolutely insistent that the universe was infinite. But he wasn't able to actually explain this. I don't see the basis for this assumption and I can't understand why it seems to be so widespread, is this some new(ish) theory that I haven't heard of? It's my understanding that the universe, as we currently know it (in other words the area effected by the big bang), extends only a few hundred thousand light years beyond

    • If you call the level 1 multiverse from the article the universe, which seems reasonable if's all subject to the same physical laws and it's theoretically possible for the universes to expand into each other, the belief appears to be that it's infinite because the physics suggests no reason big bangs wouldn't happen in infinite places.
  • After considering the concepts in the article I propose that these scientists shift into research for more effective aspirin as a careful reading of the material will leave almost all people with a glorious headache. Talk about trying to put the ocean in a paper bag!

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