What was missing from the discussion was an attempt to tackle one of the issues that plagues string theory: the math may all work out and it could provide a convenient way of looking at the world, but is it actually related to anything in the actual, physical Universe? Nobody even attempted to tackle that question.
I was surprised and happy to read this part. With my multiple attempts (and mostly failing) to understand quantum mechanics or string theory, I got the impression that this topic is never approached, and that omission never explained. If you're going to try to convince someone that our universe has multiple parallel futures, you should be ready to explain how that relates to our lives.
I think that's what lead me to the impression - as an outsider - that fascinating sounding things like the many-worlds interpretation are beautiful ideas that do not exist outside of equations, they're a kind of science fiction, a kind that is backed by mathematics and published in journals.
String theory and QM are dissimilar in this aspect. Predictions made by QM have been experimentally verified to an absurd preciseness. In fact, some of the most precise verifications ever done in science have been in QM.
Yes. In fact the whole 'many worlds' thing from QM is just an interpretation of what the equations appear to be stating. For example, in general the equations tell us with retardedly awesome precision the probability of events occurring. This is hard science. The many worlds interpretation (ie something along the lines that the universe branches at every possible 'coin toss') is one attempt at reconciling this 'non-intuitive' behavoir (that the universe is inherently probabilistic) with our intuition.
Much of the 'far off' musings in the many worlds interpretation is the result of physicists being bored and wanting to have some fun, or some popsci gone horribly wrong.
Edit: Also, if we did live in a holographic universe, there may be experimental proof of it (the ars article left it out). Ironically linking to a popsci article... (says that we probably aren't)
There fact the Universe is probabilistic isn't what MWI is needed to explain. There's nothing even especially counterintuitive about the Universe being probabilistic. MWI is a (so-far) unavoidable implication of the laws that predict real, observable QM effects. When people crunched the numbers and saw that it predicted quantum decoherence that resembles so-called "splitting" Universes (in actuality it's not a discrete process) they said, "That can't be right," and circumscribed a mysterious and ill-specified boundary beyond which the empirically validated rules don't apply.
MWI requires you believe that physics is governed by the Schroedinger wave equation. Copenhagen requires you to believe that the Universe is governed by the Schroedinger wave equation, but only when we're not looking at it, and when we look at it reverts back to the classical world through some mechanism so far unexplained, and this collapse of the quantum world into the classical world somehow produces no testable predictions that would distinguish it from what we would expect the system to look like if the wave equation just kept on working.
In other words, the MWI is what QM predicts if you assert that the observer is described by QM. So either we assert that there is some complex "collapse" mechanism which is somehow tied to observation, or we're stuck with MWI. Thus Occam's Razor says that, unless we have evidence for a complex "collapse" mechanism (hint: we don't), we should accept the MWI.
Unfortunately Everett did his work after most physicists had become comfortable with "shut up and calculate". And therefore they did not want to bother thinking about it seriously. Of the people who did think about it, many were wedded to other interpretations, and so were not inclined to accept a weird upstart.
However it is worth noting that a survey of cosmologists some years ago found that over 50% accepted the MWI. When you get away from the philosophical fringe, there is simply no other interpretation of QM whose reasoning is half as compelling as the MWI.
The Structure of Scientific Revolutions pointed this out decades ago. New paradigms tend not to win by converting existing practitioners, but instead by converting everyone entering the people and lasting until the skeptics die. I could cite a great many examples of this.
You see all of the worlds. Each copy of you has a brain state encoding the history of the path he saw. Each of you simultaneously remember being in their own unique history and are unaware of the other histories.
If you're going to try to convince someone that our universe has multiple parallel futures, you should be ready to explain how that relates to our lives.
Isn't it a bit presumptuous to demand that any theoretical truth about the nature of the entire universe should be relatable to the life of a human?
It is not presumptuous. The very human is the one pondering about this 'truth': it very well relates to him as the 'nature' of the Universe contains man within it, does it not? So whatever nature the Universe follows, so does man.
If it were the case that there are multiple parallel futures, then we ask ourselves:
How do I navigate myself to the best-possible future for me and those who surround me?
It is your very actions day by day that determine where it is that you go.
So whatever nature the Universe follows, so does man.
Sure, but that doesn’t mean that humans are able to understand nature in a way that relates to them, at least not on all levels. We weren’t built for large and small scales, our brain is only intuitively familiar with human scales. A second to a century. One millimeter to 100 kilometer. A few centimeters per day to a few dozen kilometers per hour.
I don’t think intuitiveness should be a deciding factor when it comes to describing nature.
MWI has a great deal to say about your life, as the rules that imply MWI are the exact same rules that imply chemistry. MWI is not QM with an added postulate of "Oh, by the way, everything happens." MWI is QM. Period. Decoherence unambiguously happens in the math, and nothing we have ever observed gives any reason to think the math doesn't apply to us.
Um, MWI is not QM. MWI is an elegant way of explaining the results of QM just as 6000 years ago God was an elegant way of explaining creation. It is interesting to think about but without proof of any kind it has little value.
Think about the implications of a real MWI. Real universes are not cheap, an apparently infinite supply is extremely ridiculous.
1. How do you know that "real universes are not cheap"? Are you an expert on the universe-making process?
2. The "universes" that appear in MWI are simply parts into which the universal wavefunction gets decomposed. Getting rid of them would require some sort of wavefunction-pruning process. You might equally say "Destroying universes is not cheap", a statement for which I think I have every bit as much evidence as you have for yours.
(Of course non-MW interpretations of QM do have a wavefunction-pruning process. They don't generally have much to say about how it happens, and they tend to require ridiculous things like building the notion of "observer" into the fundamental equations of physics. Or, as in the case of Bohmian QM, they include all the same mechanics as MWI plus a bit extra and then claim to be more parsimonious simply because they attach the label "real" to a different subset of what the theory talks about.)
I know they're completely different, but it still amuses me to think that not roo long ago you could have almost said the same thing about version control:
Real branches are not cheap, an apparently infinite supply is extremely ridiculous.
I love it when the "quirks" break the whole theory. This is what happened in the late 1800's; there were only minor flaws in Physics that needed to be ironed out.
Of course, when that started, the garment caught on fire.
Hawking et. al. are arguing about an idea that has equations and some sort of potential physical meaning, and in accordance with the Correspondence Principle [1] has only the most subtle of impact on the rest of physics as we know it, if true. It's an idea that can be disproved, and may have been disproved: http://www.wired.com/wiredscience/2011/07/hologram-universe/
The essay you linked to is Deepak Chopra-style quanto-babble with little content that can actually be translated into something meaningful in the real world. Indeed, one must ask the question, if "reductionist" scientists are so fundamentally wrong about everything, then how come they can so successfully predict so much? Is there some physical experiment that can be run that this will produce better predictions for?
So, I'd say the relationship is that Hawking et al are doing science, and Talbot is using their work as the seed for his internal random number generator.
I like to try and keep up with physics and am interested in astronomy but this stuff really goes straight over my head. If this is correct what are the implications?
I was surprised and happy to read this part. With my multiple attempts (and mostly failing) to understand quantum mechanics or string theory, I got the impression that this topic is never approached, and that omission never explained. If you're going to try to convince someone that our universe has multiple parallel futures, you should be ready to explain how that relates to our lives.
I think that's what lead me to the impression - as an outsider - that fascinating sounding things like the many-worlds interpretation are beautiful ideas that do not exist outside of equations, they're a kind of science fiction, a kind that is backed by mathematics and published in journals.