Thursday, July 28, 2011

Doubling Down On The Multiverse

Scientific American magazine is kind of like Men's Health these days, and as seen on its August 2011 cover, SciAm's version of "Get Rock Hard Abs" is anything having to do with the multiverse. The real existence of an ensemble of very different universes, much too far away to ever be seen, has become a popular speculation. But it's nothing more than an imaginative idea invented by well-meaning humans who seek explanations without having enough information — not terribly unlike the idea of "God."

First, some background: The idea of a multiverse originated in the 1950s, when a graduate student named Hugh Everett wrote one of the most influential Ph.D. dissertations ever. He argued that just as the electron cloud surrounding an atomic nucleus represents all possible positions for that electron (were we to pin down its location), so the entire universe, obeying the same laws of physics, must have a "universal wave function" that represents all possible configurations and courses of events within the universe. The idea took root in the form of a world that is constantly splitting or branching into different possibilities; when you decided to turn right at that intersection and collided with a bicyclist, there's another "branch" of the universe in which you turned left and got a traffic ticket. We can't observe how the other branches turn out, but some physicists believe that those branches are every bit as real as the branch you and I are currently experiencing.

Over the decades, the multiverse idea has evolved; currently there are four definitions of "multiverse" under consideration. A Level I multiverse proposes simply that our universe is infinitely large, and we can observe only a tiny region. Other regions have the same laws of physics but different distributions of matter. Therefore, with an infinite number of these regions, some of them must be similar to ours — including perhaps a world where everything is the same as our world, except you turned left at that intersection. In a Level II multiverse, the laws of physics vary from place to place; only our local "neighborhood" operates on the physical laws familiar to us. A Level III multiverse is the kind originally envisioned by Everett, where there is really only one local universe, but within that universe are an infinite number of branches — including a branch where you turn left, and some branches where the laws of physics started out completely different and matter never formed. Finally, a Level IV multiverse comprises the sum of any and all possible mathematical structures that may represent universes, with the mathematical structures themselves being fundamental or irreducible entities, not the universes they represent. In a Level IV multiverse, "self-aware substructures" (which are also fundamentally mathematical) arise — conscious beings like you and me.

Granted, Level III and Level IV multiverses are abstract and subtle. Maybe that's why, in popular science media, you hear so much more about Level I and Level II. For example, in the History Channel variety of science "edutainment," the Level II multiverse, with its vast array of distant "bubble" universes, all with different physical constants, has become the default go-to explanation for why our universe appears to be fine-tuned for the existence of matter. Fine-tuning has become a problem in physics in the last couple of decades, but the Level II multiverse offers an easy way out. If there are an infinite number of bubble universes, each with different physical laws, surely some of those would have laws that support the formation of matter, and eventually life. So, finding ourselves in such a "fine-tuned universe" should not be surprising at all.

Here is where I bristle. Yes, we do need an explanation for our peculiar and benevolent set of physical constants that's better than "a loving intelligent creator designed the universe to be that way." But let's not be ridiculous about it. Proponents of the Level II multiverse insist that other bubble universes must exist for no other reason than we find ourselves living in one such bubble. To me, that's an arrogant and small-minded conclusion to draw. As I've argued previously, it's like seeing MTV playing on your television, and then based on that one observation, concluding that there must be hundreds of invisible TV cables somehow entering your home, each carrying a different channel.

In The Trouble With Physics, Lee Smolin writes that one of the greatest powers of science is to protect humans from their own imaginations. We are very good at noticing patterns in the world and generating possible explanations for those patterns. But when we aren't given enough information — as is always the case — our creative imagination fills in the gaps. Whether it's the Earth supported on the back of a turtle, or a Judeo-Christian Yahweh dividing light from the darkness, our naive explanations tend to be fanciful. Medieval astronomers imagined the Sun and planets moving on rotating crystal spheres, but then Copernicus, Galileo, and Kepler showed that the crystal spheres weren't necessary. The same happened to the aether, the invisible medium of space that was believed to carry light waves, and which was vanquished by Einstein. This steady correction of fanciful human fabrications is the legacy of science. "More than anything else," Smolin writes, "[science] is a collection of crafts and practices that, over time, have been shown to be effective in unmasking error. It is our best tool in the constant struggle to overcome our built-in tendency to fool ourselves and fool others."

So we have the bubble universes, which are posited to "really" exist, despite being completely unobservable. If science is our best hope for unmasking wrong explanations, it can't help us here. Unchallenged, the bubble universe theory could persist for hundreds of years, as untested as Judeo-Christian creation before it, simply because it is an explanation, even if it isn't a scientific one. This is why it irks me to hear an authority in physics just lay it out, as verified truth, that distant, very different bubble universes really do exist out there — that this view explains everything. No need to think about the issue anymore; it's been solved. You've just gotta have faith!

I am reminded once again of a telling moment from Carl Sagan's Cosmos. Long ago, people wondered what was on the surface of Venus. Through a telescope, the planet was a white blur. It must be covered with clouds. If it's covered with clouds, it must rain a lot, and the surface must be wet and swampy. If it's swampy, there must be swamp creatures, maybe even dinosaurs. As Sagan put it, "Observation: Can't see a thing. Conclusion: Dinosaurs." The crazy collection of unobservable bubble universes thought to be out there are today's Venus dinosaurs. In 100 years, we will laugh at the naivete and arrogance of this colorful, if incredibly small-minded, conception. Science moves on, forever banishing the errors of the human imagination. In this case, it's a sure thing.


  1. Not surprising they would have to resort to this. Magazines are dying.

  2. Did you read Stephen Hawkins' last book, The great design? He seems to support the multiverse idea based on quantum physics.

  3. Right; a lot of people do. It's an attractive way to deal with the many difficulties of quantum mechanics. Others (I'm talking about mainstream physicists such as Paul Davies) dispute the multiverse and/or the ontological "realness" of the multiverse. There's a spectrum of opinion. While I am not a physicist, I'm most attracted to the far end, the side that believes a multiverse is a theoretical, mathematical reality only and has no independent ontological existence.

  4. I agree that (at least at this stage of the game) the idea of a multiverse is more philosophy than physics.

    You don't need a multiverse to explain why our universe seems fine-tuned. Going back to our old(but reliable) buddy, the anthropomorphic principle, if this particular manifestation of a universe weren't *just right*, then we wouldn't be here to speculate about it in the first place.

  5. If total energy of the universe is zero, as claimed by some scientists, then based on this data it can be shown that multiverse theory is probably not true. This is because total energy being zero, total mass will also be zero due to mass-energy equivalence. Scientists have shown that anything having mass will always occupy some space. So anything that fails to occupy any space cannot have any mass. Our universe perhaps fails to occupy any space, and that is why its mass is zero. But if multiverse theory is true, then our universe will definitely occupy some space within the multiverse, and thus in that case its mass cannot be zero. But as this mass is zero, therefore multiverse theory cannot be true.
    Here it may be argued that radiation occupies space but its mass is zero. So here is an example that something occupying space can still be without mass. So our universe can also be without mass even if it occupies some space within the multiverse. In reply we will say that the example cited here is a bad example, because our universe is not any kind of radiation. So if it is without mass, then that can only be due to its not occupying any space, and not due to its being some sort of radiation.
    However, if total energy of the universe cannot be taken to be zero, then the conclusion drawn here will not stand. In that case multiverse theory may be true, but we cannot say whether it will be necessarily true.

  6. That's interesting, but I have a problem with one step: "if multiverse theory is true, then our universe will definitely occupy some space within the multiverse." If our universe perhaps fails to occupy any space (which is possible, as some of the more radical theories of quantum mechanics assert that space cannot exist at a fundamental level), why would it definitely occupy some space within the multiverse? I think a rigorous definition of 'space' is required here.

  7. I agree with your basic problem with this, primarily, that these concepts are not falsifiable and as such no better than (gasp) religion. I have a problem with using a multiverse to explain the quantum effects in the double slit experiment. It violates ockham's razor. I think a simpler solution currently eludes us.

  8. If multiverse theory is true, then there are definitely other universes, probably an infinite number of them, lying outside our universe. All these universes collectively are in some superspace or hyperspace. This superspace or hyperspace must be infinite in extension, otherwise how can it accomodate an infinite number of universes? So if multiverse theory is true, then our universe will be within this superspace or hyperspace. But suppose that multiverse theory is not true, and that our universe is the sole universe that is there. In that case there will be nothing outside our universe, no space, no time, no matter and not even a single other universe. Our universe as a whole will be neither in space nor in time, and therefore as a whole it will be spaceless and timeless. As it will be in no space, so we cannot say that as a whole it will occupy any space. And if it is true that anything having some mass will always occupy some space, then our universe sa a whole failing to occupy any space will have no mass.

    God is mostly described as spaceless and timeless. Here we have seen that if our universe can be considered as one whole unit, then it can also be described as spaceless and timeless. This whole unit will comprise anything and everything that is there, and there will be nothing outside it. So if quantum theorists are saying that space cannot exist at a fundamental level, then multiverse theory must be false, because in that case only our universe will be the sole universe, and then only our universe will be a spaceless universe.

    If quantum theorists are saying that space cannot exist at the fundamentel level, then I think that at the same time they are also saying that time cannot exist at the fundamental level.

  9. uchitrakar -- I'm still not convinced. I need to see a rigorous definition of space, time, and "exists" in order to follow your argument. You've made some leaps, for example going from "probably an infinite number of them" to "must be infinite in extension." And I don't get the argument that if space and time do not exist outside of our universe, then our universe itself must be described as spaceless and timeless.

    Here is an essay by Fotini Markopoulou (it won an FQXi prize) arguing that fundamental space does not exist but fundamental time does.

  10. My purpose is to show that multiverse theory is false. If Fotini Markopoulou has argued that fundamental space does not exist, then that will serve my purpose. Fundamental space does not exist means space is emergent, and therefore space cannot pre-exist before the origin of the universe. It will come into being along with the birth of the universe, and again it will become non-existent when the universe dies down. But if multiverse theory is true, then we will have to assume that there is already some sort of pre-existing space within which universes will be accommodated one after another after their origin from the big bangs, and these big bangs will also take place one after another. Here one universe within the multiverse may die down at any time, but that will not indicate end of all space, because there will be other universes left within the multiverse, and thus there will still be space within it. Only if there is one single universe, then in that case we can say that space does not exist at the fundamental level, because in that case space will be emergent with the birth of the universe only. No birth of universe means no space. So one single universe can satisfy the condition that fundamental space does not exist, but not the multiverse.

    It is the view of most of the scientists that before the big bang there was no space and no time, space and time came into being along with the birth of the universe only. According to this view both space and time are emergent, and therefore neither space nor time can exist at the fundamental level. But if it is true that only fundamental space does not exist but not fundamental time as per Fotini Markopoulou, then in that case space will only be emergent but not time. That will mean that space only came into being along with the big bang but not time. That will further mean that there was time before the big bang. This will further mean that this big bang was not the only bang that took place 13.7 billion years ago, but that there were unending numbers of big bangs and big crunches before this bang, which fully supports the view of some Hindu seers who many centuries ago had proclaimed that Brahman the Supreme Being created this type of universe from within Himself (Big Bang) many many times, and then again after certain period of time took everything of the created world back into Himself (Big Crunch), and that also many many times, and this cycle of creation and destruction will go on and on unendingly.

    By definition universe is that which comprises everything. By definition it is that outside of which there cannot be anything. Now let us suppose that we want to determine how the universe as a whole is changing with time. Please keep it in mind that here we have used the term “universe as a whole”. Let us denote the term “universe as a whole” by U. If we want to determine how U is changing with time, then we will have to first place it in some time co-ordinate. Then only we will be able to determine its change with time. But this time co-ordinate cannot be within the universe, because we have already decided that we will determine the change of U with time, and not the change of any part of it with time. So U will have to be placed in some time co-ordinate and not any part of it, and therefore this time co-ordinate must have to be outside the universe. But by definition there cannot be anything outside the universe, and therefore there cannot be any time co-ordinate in which U can be placed. So how the universe as a whole changes with time can never be determined. And therefore we will have to admit that it is in a timeless state, because it is in no time. If it was really in time, then it would also have been possible for us to determine its changes with time. As it is not possible for us to determine these changes, so we will have to admit that it is in a timeless state. For the same reason we will have to admit that it is in a spaceless state also.

  11. Rigorous definition of space and time can only be given by the scientists only, that cannot be given by a layman like me. However I can always try to draw some legitimate conclusions from the conclusions they have arrived at from their various experiments and observations. If Fotini Markopoulou has shown that time can exist at the fundamental level but not space, then its logical conclusion is that there was time before the big bang, which is in marked contrast with the prevailing opinion among the scientific community that holds that time began from big bang only.
    The idea that the universe when considered as one whole unit can be said to be in a spaceless and timeless state is not mine at all. I first got this idea from an article written by the scientist Dr. Lee Smolin and read in the internet. But I have lost the article and with it the reference also.

  12. There is one more reason as to why multiverse theory cannot be true. Scientists repeatedly say that total energy of the universe is zero. It started from zero energy, and its total energy throughout remains constant at initial zero value. No extra energy added, no energy subtracted. The lesson to be learnt from this is that whatever will be at the beginning will be at the end also. But if no energy can be added to the universe from any outside source, then why shall we have to believe that other entities like space, time, mass can be added? So if universe started from zero space, then its total space will always remain zero. That means that universe will have no extra space outside it, and as a result universe as a whole will not occupy any space. But if multiverse theory is true, then there will have to be extra space in between universes. But if no extra space can be added from outside, then whence will appear that extra space? And so, multiverse theory cannot be true.

  13. Multiverse: A very imaginative idea created by Physicists who don't understand Shakespeare.

  14. The multiverse doesn't need to be in the form of "bubbles" separated in space or something like that. I could imagine that the multiverse has a fractal nature, so when you "zoom" in or out, you will arrive at another universe with different laws of physics. Or that the different universes are separated by time, so when our universe dies, another comes to existence. Etc. etc.
    But this is all speculation which we might never find the truth about. I just find the idea of the abstract concept of a multiverse (II) a convincing explanation to the fine-tuning problem.