Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Why we think there's a Multiverse, not just our Universe

scienceblogs.com

Post reply on HN
Print view View original

51–57 of 57 posts

Re: Why we think there's a Multiverse, not just our Universe

#51

Post by gizmo »

Confusion wrote: post #46

As the only criticism on this article has been downvoted strongly, I feel compelled to repeat my explanation of that criticism (that believing in the multiverse is like believing in heaven or hell) at a higher level, in the hopes that people will be somewhat more critical of what esteemed scientists are peddling as truth: There is not a shred of experimental evidence for the multiverse. In fact, experimental evidence…

Assertions that take the form "X is like religion" are not enlightening. When it is prefaced with "get the facts straight" then of course it's going to get downvoted. There is nothing being "peddled" here, there is no hidden agenda by "esteemed scientists".

We have experimentally demonstrated that the universe is a really, really weird place. Time and space can bend. Whoah. But hey, we proved that beyond a shadow of a doubt. Then there's quantum mechanics. Wave functions! Entanglement! Turns out the universe really works that way. Then the universe starts looking really non-deterministic. Then we figured out that the simplest interpretation of QM implies Many Worlds, that the universe splits and splits and splits into a bazillion near-copies. The quantum events just look non-deterministic from our perspective. Do we know everything? Hell no. But we know that QM is true and that it uses some form of Many Worlds. We know that the world is deterministic. We don't know for sure how the universe came into being (but we are sure the universe is expanding). We don't know if there really is such a thing as the multiverse, but as we figure out more about the big bang, about background radiation, about black holes and dark matter and the shape of our universe there's a good chance we'll figure it all out eventually.

Physics is treading on the domain of philosophy because we're getting better at physics. Philosophers debated since the dawn of time about free will and didn't get anywhere. Now we know that non-reductionist or dualistic world views make little sense. Philosophers debated for ages about morality. Now neuroscience is starting to deliver concrete answers. Philosophers debated for ages about religion and heaven/hell. And elementary Bayesian math shows the questions are just nonsensical.

Philosophy is about reasoning about topics we don't really understand. As our understanding of physics, math, neuroscience and biology grows philosophy has to make way.

Re: Why we think there's a Multiverse, not just our Universe

#52

Post by rms »

I cannot recommend the writings of Max Tegmark on the multiverse enough. Among people doing science at the heights of their fields, he is perhaps a uniquely talented popular writer. He even keeps it readable on his scientific papers, which read mostly just like his popular papers except shorter and with more math.

http://arxiv.org/PS_cache/arxiv/pdf/0905/0905.1283v1.pdf is his overview of the levels of multiverses.

If that properly blows your mind, see Bostrom's Infinite Ethics. http://www.nickbostrom.com/ethics/infinite.pdf

Re: Why we think there's a Multiverse, not just our Universe

#53

Post by Confusion »

gizmo wrote: post #51
Confusion wrote: post #46

As the only criticism on this article has been downvoted strongly, I feel compelled to repeat my explanation of that criticism (that believing in the multiverse is like believing in heaven or hell) at a higher level, in the hopes that people will be somewhat more critical of what esteemed scientists are peddling as truth: There is not a shred of experimental evidence for the multiverse. In fact, experimental evidence…

Assertions that take the form "X is like religion" are not enlightening. When it is prefaced with "get the facts straight" then of course it's going to get downvoted. There is nothing being "peddled" here, there is no hidden agenda by "esteemed scientists". We have experimentally demonstrated that the universe is a really, really weird place. Time and space can bend. Whoah. But hey, we proved that beyond a shadow of…

  Then we figured out that the simplest interpretation of QM
  implies Many Worlds
Many physicists contend this point. They do not consider this interpretation as 'the simplest'. Things hinge on such contentious points as the physical reality of 'the collapse of the wavefunction'. Again, the major thing the Many World interpretation has going for it is that it easily appeals to our imagination -- even, or especially, to the imagination of non-physicists.

  We know that the world is deterministic.
Philosophers disagree. It's even the question whether this issue can possibly be settled by any experimental evidence, because of the way we, and our math, are wired to consider everything in causal chains. The evidence isn't really very compelling if you consider the fundamental problems surrounding the question.

  Now we know that non-reductionist or dualistic world views
  make little sense
Descartes has been critiqued extensively long before science could say anything about mind-matter interactions, because the main shortcomings of the duality argument do not depend on any experimental facts at all.

  Now neuroscience is starting to deliver concrete answers.
On the subject of morality, neuroscience cannot possibly deliver any concrete answers at all. You're engaging in the naturalistic fallacy if you think it does. What is the case in the world is not argument for what should be the case in the world. Neuroscience may explain why people hold certain ethical views. It can never explain what ethical view they should hold. What view is 'acceptable', 'the best', 'right'. The answer to that question cannot be reduced to physical facts about the universe.

  Philosophy is about reasoning about topics we don't really
  understand.
Then we don't really understand logic and math either, do we? The foundations of logic and math are still part of philosophy after all.

And, well, Hume didn't really understand causality, did he? But fortunately, thanks to modern physics, now we do?

Re: Why we think there's a Multiverse, not just our Universe

#54

Post by gizmo »

Confusion wrote: post #53
gizmo wrote: post #51

Earlier quoted context omitted.

Assertions that take the form "X is like religion" are not enlightening. When it is prefaced with "get the facts straight" then of course it's going to get downvoted. There is nothing being "peddled" here, there is no hidden agenda by "esteemed scientists". We have experimentally demonstrated that the universe is a really, really weird place. Time and space can bend. Whoah. But hey, we proved that beyond a shadow of…

Then we figured out that the simplest interpretation of QM implies Many Worlds Many physicists contend this point. They do not consider this interpretation as 'the simplest'. Things hinge on such contentious points as the physical reality of 'the collapse of the wavefunction'. Again, the major thing the Many World interpretation has going for it is that it easily appeals to our imagination -- even, or especially, to…

> Many physicists contend this point [ ... ] appeal to imagination.

Not so. The vast majority of quantum physicists now agree Many Worlds has won, including Feynman, Gell-Mann and Hawking. The concept of 'collapse of the wavefunction' is silly and shouldn't even be considered for reasons outlined here: http://lesswrong.com/lw/q8/many_worlds_one_best_guess/

> Determinism; Philosophers disagree.

It's just basic reductionism. There are absolutely no fundamental problems surrounding this.

> On the subject of morality, neuroscience cannot possibly deliver any concrete answers at all.

All moral thought and all moral beliefs up to now have happened inside the human brain. Most moral thought is confused and self-contradictory. If we want to figure out why we are moral the way we are, what our "true" moral beliefs are, and how to build societies that flourish, we have to look inside the brain to see how it all works. Either morality has bearing on the real world and is therefore subject to measurement or it has no bearing on the real world and is therefore irrelevant.

> Then we don't really understand logic and math either, do we? The foundations of logic and math are still part of philosophy after all.

Where the line is drawn between math/philosophy isn't a very interesting question.

> And, well, Hume didn't really understand causality, did he? But fortunately, thanks to modern physics, now we do?

Nope. And yep. And thanks to Bayesian reasoning.

Re: Why we think there's a Multiverse, not just our Universe

#55

Post by guscost »

Confusion wrote: post #46

As the only criticism on this article has been downvoted strongly, I feel compelled to repeat my explanation of that criticism (that believing in the multiverse is like believing in heaven or hell) at a higher level, in the hopes that people will be somewhat more critical of what esteemed scientists are peddling as truth: There is not a shred of experimental evidence for the multiverse. In fact, experimental evidence…

I could not agree more. We don't all believe in a multiverse.

Re: Why we think there's a Multiverse, not just our Universe

#56

Post by Confusion »

gizmo wrote: post #54
Confusion wrote: post #53

Earlier quoted context omitted.

Then we figured out that the simplest interpretation of QM implies Many Worlds Many physicists contend this point. They do not consider this interpretation as 'the simplest'. Things hinge on such contentious points as the physical reality of 'the collapse of the wavefunction'. Again, the major thing the Many World interpretation has going for it is that it easily appeals to our imagination -- even, or especially, to…

> Many physicists contend this point [ ... ] appeal to imagination. Not so. The vast majority of quantum physicists now agree Many Worlds has won, including Feynman, Gell-Mann and Hawking. The concept of 'collapse of the wavefunction' is silly and shouldn't even be considered for reasons outlined here: http://lesswrong.com/lw/q8/many_worlds_one_best_guess/ > Determinism; Philosophers disagree. It's just basic reducti…

Concerning Many Worlds:

Firstly, [1] disagrees with you. Secondly, there is a difference between accepting MWI above other interpretations and actually believing in multiple parallel universes. A difference between accepting the physical and the metaphysical consequences. Thirdly and crucially, MWI depends on QM. Everyone acknowledges QM is probably not a definite description of the universe and non-locality, non-contextuality or another kind of modification would wreak havoc on MWI. If physicists subscribe to MWI but also acknowledge QM seems incomplete, they are being inconsistent.

Concerning determinism:

You say "it's just basic reductionism". But in fact it presupposes reductionism as a viable strategy to determine 'the truth' about determinism. It isn't [2]. Specifically, the question whether we can even determine whether our fundamental theories are deterministic is still wide open. None of the theories, from classical mechanics to quantum mechanics, is clearly deterministic and it remains a question whether it can even be determined whether they are deterministic.

Concerning morality:

No matter how well you can 'measure' my 'true' ethical views on abortion: no measurement will ever tell you what my ethical view on abortion should be. No collection of measurements will ever tell you what a governments policy on abortion should be. At most you can hope to be able to say: in this particular case we should allow it, because that will be best for everyone: the average happiness, productivity and insert-factor-of-importance will be highest if we allow it. However, that kind of judgment presupposes a certain moral system. You can never determine which factors should be important. At most you can measure which factors people rate as most important on average. But again, you presuppose a certain moral system if you choose to use that measurement to determine what to do. If you feel otherwise, there's a large philosophical nut left for you to crack.

I think you underestimate the complexity of these subjects and that your verdicts are premature.

[1] http://en.wikipedia.org/wiki/Many-worlds_interpretation#Rece...

[2] http://plato.stanford.edu/entries/determinism-causal/

Re: Why we think there's a Multiverse, not just our Universe

#57

Post by Umofomia »

Confusion wrote: post #56
gizmo wrote: post #54

Earlier quoted context omitted.

> Many physicists contend this point [ ... ] appeal to imagination. Not so. The vast majority of quantum physicists now agree Many Worlds has won, including Feynman, Gell-Mann and Hawking. The concept of 'collapse of the wavefunction' is silly and shouldn't even be considered for reasons outlined here: http://lesswrong.com/lw/q8/many_worlds_one_best_guess/ > Determinism; Philosophers disagree. It's just basic reducti…

Concerning Many Worlds: Firstly, [1] disagrees with you. Secondly, there is a difference between accepting MWI above other interpretations and actually believing in multiple parallel universes. A difference between accepting the physical and the metaphysical consequences. Thirdly and crucially, MWI depends on QM. Everyone acknowledges QM is probably not a definite description of the universe and non-locality, non-con…

BTW, you guys keep talking about MWI, while the original article is categorically not about MWI. The author describes a Tegmark Level I Multiverse[1], the most conservative of the multiverse models. MWI is Level III, and the author himself says in a subsequent comment[2]:

  What I've presented, above, is the argument for the first
  type of Multiverse, which I think is correct, and hence,
  which I believe in.
  
  I think that anything beyond that is too speculative to be
  believed at this point, at least with any sort of
  confidence. At least, by me.
[1] http://en.wikipedia.org/wiki/Multiverse#Level_I:_Beyond_our_...

[2] http://scienceblogs.com/startswithabang/2011/10/why_we_think...

Post reply on HN