Explaining the Quantum Mystery: Are Parallel Universes the Answer?

Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
103 replies · 17K views
Art said:
I never mentioned good or bad decisions :confused:
I used the word 'decisions" in place of your "paths". Choosing a path is making a decision.
 
Astronomy news on Phys.org
SpaceTiger said:
Of course, subjective experience can throw a wrench into all this with things like quantum immortality, but then the discussion ventures from science as we know it. If the outcome of an experiment cannot be objectively agreed upon, there's not much point in performing it.

That means your are not willing to pull the trigger? :smile::smile:
 
Evo said:
I used the word 'decisions" in place of your "paths". Choosing a path is making a decision.
It's the 'good' and 'bad' I referred to as irrelevent.

Read Vanesch's replies to my post. He understands my point and his replies may help clarify it for you.
 
Art said:
It's the 'good' and 'bad' I referred to as irrelevent.

Read Vanesch's replies to my post. He understands my point and his replies may help clarify it for you.
I read his reply. He was responding to a different point.

I was responding to this post of yours

Art said:
so why is it that when you look back over your life nearly all the paths you ended up on happened to represent the most likely? Also it follows that if the 'primary' you hogged all of the most likely paths your doubles were left to take the less likely paths so when they look back over their lives they would see a string of unlikely happenings.
Go back and read my response as it pertains to this statement of yours.
 
Evo said:
I read his reply. He was responding to a different point.

I was responding to this post of yours

Go back and read my response as it pertains to this statement of yours.
Evo it doesn't! I'm talking about probabilities whereas you are talking about good and bad life choices. The two are a universe apart :biggrin:
 
Art said:
Moonbear imagine you are walking down a road and it forks into 2, suddenly there are also 2 of you. One takes one turn and the other you takes the other. Next these 2 come to another set of forks so there are now 4 yous each on one of the new tracks. This continues on until there zillions of you.

Now at each junction there was a 50:50 chance which path the 'primary' you ended up on as you had no way of knowing which path represented the most likely (as you had no knowledge or say in the universe splitting) so why is it that when you look back over your life nearly all the paths you ended up on happened to represent the most likely? Also it follows that if the 'primary' you hogged all of the most likely paths your doubles were left to take the less likely paths so when they look back over their lives they would see a string of unlikely happenings.
What makes you assume any path was more "likely" than the others, though? That's what I don't understand about what you're saying. If I went right instead of left, why would I look back from either and think there was anything "unlikely" or "likely" about what path I wound up on, as long as the two options were possible? It's not like one path had a brick wall in the middle of it, and I somehow wound up on the other side of the wall without having ever climbed it.

Sticking with life's choices as the example, I'm not even sure I ever have taken the "likely" path. It certainly hasn't been my predicted path. I'd have to guess that somewhere in another universe, there's one of me who is an M.D., married, 1 kid, living in a big house with a dog as a pet, a housekeeper, and comfortably wealthy living off inheritance money, because those are the paths I didn't take along the way when various opportunities were presented. There's nothing more or less likely about that had I wound up on that path rather than the one I did end up choosing. In fact, with my background, this analogy would also mean there's a universe with one of me who never went to college, and took over my dad's carpentry business right out of high school. Had I wound up on that path, again, how would I look back and think there was anything less likely about it than the path I wound up on? How would I know this path was ever a possibility to even realize I missed something at one of those turns? I think you're also assuming an awareness of all the possible outcomes at every step of the decision/bifurcation process that doesn't need to exist. I guess for the mathematical model to work, there needs to be knowledge of the decision points on behalf the mathematician (which makes it pretty untestable if you can't know all the decision points), but that doesn't mean someone making those decisions is aware they had the choice to take a path other than the one they took. How often, when you're walking somewhere, do you stop and think, "Gee, I could have turned left there instead of right...why didn't I, and how will that impact my entire future? What if I missed some golden opportunity that was just waiting for me to the left and it's now too late?"
 
Art said:
Now at each junction there was a 50:50 chance which path the 'primary' you ended up on as you had no way of knowing which path represented the most likely (as you had no knowledge or say in the universe splitting)

How is this applicable? The entire purpose of quantum theory is to determine probabilities for individual outcomes. MWI simply provides a possible explanation for why we can't make those probabilities into certainties.
 
Art said:
Evo it doesn't! I'm talking about probabilities whereas you are talking about good and bad life choices. The two are a universe apart :biggrin:
No, I am asking you why you are making these assumptions. You've made the same assumptions in several posts.

Art said:
Moonbear imagine you are walking down a road and it forks into 2, suddenly there are also 2 of you. One takes one turn and the other you takes the other. Next these 2 come to another set of forks so there are now 4 yous each on one of the new tracks. This continues on until there zillions of you.

Now at each junction there was a 50:50 chance which path the 'primary' you ended up on as you had no way of knowing which path represented the most likely (as you had no knowledge or say in the universe splitting) so why is it that when you look back over your life nearly all the paths you ended up on happened to represent the most likely? Also it follows that if the 'primary' you hogged all of the most likely paths your doubles were left to take the less likely paths so when they look back over their lives they would see a string of unlikely happenings.
Why do you keep making this assumption? I was (and still am) hoping you will explain why you think this. Looking back at my life, I don't see that "nearly all the paths I ended up on happened to represent the most likely". I think a lot of people would agree that they ended up on some very unlikely paths. I certainly did. I never would have chosen this career, I got sucked into it, and I will never forgive myself for not going against my father and going into science which was my passion for all of my life.
 
I will never forgive myself for not going against my father and going into science which was my passion for all of my life.
You don't need to let it go; just make it Evo's problem in a parallel universe. :smile:
 
I think you are taking my metaphor too literally. It is not about life choices it is about pure chance such as whether or not you get struck by lightning during a storm. To keep it simple there are 2 possibilities either you are or you are not. The most LIKELY outcome is you are not but because there is a very slight chance you are the universe needs to split to cover that eventuality and so your double is struck by lightning. Throughout your life there are many similar instances where the universe would split to cover equally unbalanced events and invariably it is your double who suffers the UNLIKELY consequence whereas if the path after the split was truly random in a 2 choice scenario 50% of the time it should be you.

The path = the passage of time
The forks = splits in the universe
 
Last edited by a moderator:
Art said:
I think you are taking my metaphor too literally. It is not about life choices it is about pure chance such as whether or not you get struck by lightning during a storm. To keep it simple there are 2 possibilities either you are or you are not. The most LIKELY outcome is you are not but because there is a very slight chance you are the universe needs to split to cover that eventuality and so your double is struck by lightning. Throughout your life there are many similar instances where the universe would split to cover equally unbalanced events and invariably it is your double who suffers the UNLIKELY consequence whereas if the path after the split was truly random in a 2 choice scenario 50% of the time it should be you.
Funny you should choose the lightning scenario. I have been "hit" by lightning, according to a tv program about it, they count people as being indirectly hit through phone lines and plumbing, etc... to have been hit. I've been hit twice and my house hit once. I barely escaped a third hit by jumping into my car just in time, I felt my hair rise up, then a loud boom and saw dirt flying up in the air where the lightning hit the ground near my car. So there.
 
Art said:
I think you are taking my metaphor too literally. It is not about life choices it is about pure chance such as whether or not you get struck by lightning during a storm. To keep it simple there are 2 possibilities either you are or you are not. The most LIKELY outcome is you are not but because there is a very slight chance you are the universe needs to split to cover that eventuality and so your double is struck by lightning.
First, why is it more "likely" that you won't get struck by lightening? You seem to be assigning weight to the probabilities that doesn't necessarily exist.

Throughout your life there are many similar instances where the universe would split to cover equally unbalanced events and invariably it is your double who suffers the UNLIKELY consequence whereas if the path after the split was truly random in a 2 choice scenario 50% of the time it should be you.
Only perhaps because you're one of the "lucky" doubles. What about the people who DID get struck by lightning, or killed in a car accident, or caught in a tornado, or drowned in a tsunami? Their doubles are the "lucky" ones in each of those cases. And, the SAME double doesn't have to have ALL the bad things happen to them. Once a split has happened, every individual along that split doesn't now need to be subject to the choices of every other individual that arose from the same origin. Once you've died in one of the multiple universes, your later homicidal rampage in another universe has no impact on the universe in which you no longer exist, nor does it even impact the one just split off one before the one in which you took a blow to the head leading to the brain damage that led to the possibility of you becoming homicidal. And, just because you survived walking around in a storm without being struck by lightning, and your "double" somewhere else did get struck by lightning, doesn't mean someone in that same universe as your double gets struck by lightning the next time someone in our universe avoids getting struck by lightning while standing under a tree in a storm. And, partly, this is because there is no requirement that every split be only a bifurcation. From what ST and Vanesch have been describing, if there are 5000 places that lightning could strike from a particular cloud to the area where you are standing, there will be 5000 universes, and only in one of those does the lightning hit the spot where you are standing, while in the 4999 other universes, it hits someplace near you, but doesn't actually strike you. So, it's not just 50/50 that it hits you or not, but more like 1/5000 that it hits the precise spot where you're standing. The odds get even longer if you're walking around and more universes are popping up with every step you take, so that the probability of lightning hitting you requires being in the one universe out of millions where you took that step to the left just moments before the lightning hit that spot out of all the other spots it could have hit.
 
In another universe, MB built an addition on my house in an exchange for me putting 'gravity to electric' panels on her roof.
 
In another universe, sheep are the highest order of life, and pigs can fly. The sheep are jealous.

OK - this is more like the GD Universe with which I am comfortable. For a moment, this thread started out seriously.

Back to normal. :Phew!:
 
Art-- I think you are asking "is the totality of all universes a fair place?" That's kind of like asking "is life fair?" and we all know the answer -- or can expect to learn (painfully) at some point.

What took me down this path is the thought that every time a coin is flipped, if it's "heads" in this universe then it's "tails" in another. And the other way around.

Suppose we observe 2/3rds of the outcomes as heads. We would not automatically conclude that the coin is not a random coin. We'd say it's not a fair coin, or the coin is biased. But that's not the same as a non-random coin.

With this biased coin, we get 2 heads out of every 3 tosses, on average. So in an alternative universe our copies are getting 2 tails out of 3 tosses. Are you saying that this makes our universe a special place? Because, I disagree. By your reasoning, folks in the alternative universe have the exact reason for thinking that theirs is a special universe. In some sense that's true, because each universe is unique in some way (heads vs. tails). But in another sense, they are equally mundane.
 
Last edited:
Don't believe what you read in New Scientist

qspeechc said:
I am no physicist, but it sounds like this is pretty big. From the last paragraph, it sounds like a hypothesis to me.

The second-hand story you quoted appears to based upon a story (which I haven't seen) in New Scientist, or perhaps upon a press release put out by New Scientist. In either case, you should know that New Scientist, which was once a respectable news magazine, is now regarded by many prominent physicists as sensationalist trash; see for example
http://golem.ph.utexas.edu/category/2006/09/a_plea_to_save_new_scientist.html
http://golem.ph.utexas.edu/category/2007/09/the_virtues_of_american_scient.html#more

The story didn't cite a paper or eprint and it is so vague that without reviewing recent papers by the physicists mentioned in the story, I can't guess what they are talking about. FWIW you would look for something similar to but much more recent than this 2001 eprint by David Deutsch on the multiverse hypothesis:
http://www.arxiv.org/abs/quant-ph/0104033
Deutsch and Everett are well known researchers, but it seems fair to say that the many-universes hypothesis is currently preferred by a very small minority of physicists, and I know of no reason why that might be about to change.

Tentative conclusion: this sounds to me very much like the kind of misleading "buzz" which all too often results when
1. Some university publicist overhypes a fairly ordinary paper by some faculty member,
2. An inflated and vague university press release is picked up by an uncritical news magazine (NS currently being one of the worst offenders).
3. That story is then summarized uncritically by some wire service, and this item is printed in random newspapers experiencing a "slow news day".
4. The crankweb picks up and uncritically repeats this item.
5. Someone writes a Wikipedia article which misleadingly portrays fringe claims as a widely accepted hypothesis or even as established scientific fact.

As a general rule, a good skill to learn is googling for press releases with content similar to what you are reading. Often you will find that some newspaper (or general audience magazine or website) has published with minimal changes something written, not by a scientist, but by a publicity agent working for the employer of a scientist. Needless to say, such stories are never unbiased and are almost always scientifically inaccurate.
 
Last edited:
Chris Hillman said:
it seems fair to say that the many-universes hypothesis is currently preferred by a very small minority of physicists, and I know of no reason why that might be about to change.

As has been mentioned here in this thread before, the value of an idea is not necessarily related to the popularity amongst scientists over it ; especially if it is more a philosophical issue than a genuine scientific (that means: prediction/observation and no "story") idea. Now I know that relativists for one are not the most favorable to MWI ; on the other hand, string theorists usually are. And for 99% of all working physicists, mainly working in more applied branches of physics and engineering, it really doesn't matter, and most of them haven't given it a lot of thought. So depending on your original sample of physicists, you'll find different outcomes for your poll.

That said, I agree 100% with you about Deutsch's hype and overselling.

As I said before, MWI is not an "imported idea", it emerges naturally when you take the linear quantum formalism literally, and its axioms as describing an ontological part of nature, instead of a formalism that allows you to obtain outcomes without any descriptive force. As such, MWI is to quantum mechanics, what the "block spacetime" is to general relativity (and has also its share of philosophical weirdness to it).
 
vanesch said:
And for 99% of all working physicists, mainly working in more applied branches of physics and engineering, it really doesn't matter, and most of them haven't given it a lot of thought.

Which often seems to be the case with the most interesting questions of all!

Some years ago when I set out to determine the state of the measurement problem - looking for a consensus, if any - I found that most physicists wouldn't talk about it. That is partly how I landed here at PF.
 
Last edited:
Clarification

vanesch said:
As has been mentioned here in this thread before

Clarification: I was trying to introduce into the thread some considerations which hadn't been expressed, not to summarize those which had already been discussed.

vanesch said:
the value of an idea is not necessarily related to the popularity amongst scientists over it ; especially if it is more a philosophical issue than a genuine scientific (that means: prediction/observation and no "story") idea.

Not sure I entirely agree with the premise that an idea has a well-defined value :wink: but I do agree that the arguments over the foundations of quantum mechanics involve interpretation of mathematics and (therefore?) involve philosophical issues.

vanesch said:
As I said before, MWI is not an "imported idea", it emerges naturally when you take the linear quantum formalism literally, and its axioms as describing an ontological part of nature, instead of a formalism that allows you to obtain outcomes without any descriptive force. As such, MWI is to quantum mechanics, what the "block spacetime" is to general relativity (and has also its share of philosophical weirdness to it).

Not sure I agree with the analogy, but agree that things like closed timelike curves in Lorentzian manifolds do present a challenge to the physical interpretation of such spacetimes. It might also be worth mentioning that the dividing line between classical physics and quantum physics has been increasingly blurred as mathematicians have discovered more and more analogies/generalizations unifying various mathematical ideas underlying "quantum" and "classical" physics, and as physicists have found more and more applications of "quantum physics" notions in "classical physics".

Ivan Seeking said:
Which often seems to be the case with the most interesting questions of all!

I dare say that we've all had similar experiences at one time or another. Resistance from individual scientists to contemplating profound changes can be frustrating if you want to discuss a foundational issue, but is not neccessarily "non-adaptive". In fact, from the perspective of each individual scientist, spending his time/energy wisely makes good sense. Even from the broader perspective of the healthy growth of science itself, it is not clear that this phenomenon of strong resistance to foundational revolutions is a bad thing (dunno whether that is what you were getting at). Imagine the mess if we tried to change the foundations every decade!
 
Last edited:
Ivan Seeking said:
Which often seems to be the case with the most interesting questions of all!
I guess that depends on what you think is interesting. :biggrin: I don't think anyone could stand to stay in any line of research, be it experimental or theoretical, if they didn't think they were studying something of great interest.

Chris Hillman said:
Resistance from individual scientists to contemplating profound changes can be frustrating if you want to discuss a foundational issue, but is not neccessarily "non-adaptive".

I think that's a good point. It's easy to lose perspective on that if you're among those trying to introduce something that goes completely against the grain of the "popular" opinion in a field. But, having to overcome that resistance (skepticism even) is what ensures your idea really is a solid one...resistance is fundamental to good science, and one should even be resistant to their own ideas to ensure it is rigorously tested and sound before it gains greater acceptance. If it's really a good idea, you WILL overcome that resistance eventually, and the idea will be accepted. On the other hand, if your critics are right in their doubt, that will be revealed as well when you cannot overcome their criticisms, and it'll fall by the wayside. It's important to remain humble enough to accept that you could be wrong, and to consider your critics' concerns carefully. The worst science I've seen comes from those whose egos have gotten so large, and have become so entrenched in the notion that their theory/model/hypothesis/interpretation is the right one that they are no longer objectively testing it, but simply seeking confirmation of their own opinions while rejecting any evidence to the contrary. When you stop being your own worst critic, it's time to step back and reevaluate your approach and question your objectivity.

So, I'm really glad you brought up that point, because it gave me a chance to get up on my soapbox and give that little lecture to all the budding young scientists around here (and perhaps even to a few old curmudgeons reading along who needed a reminder of this). :biggrin:
 
I wasn't suggesting that we adopt a new worldview, I was just asking about the state of the problem and opinions. In the end I found that wrt the measurement problem, for example, there was no consensus, which may be why many scientists resist any discussion. But I think this resistance also goes to the heart of what drives people.

MB, I realized before graduating that what most interests me in physics is not what interests most physicsts. To me the deep and profound questions are by far the most interesting ones. These questions are the reason that I have a degree. They are also the questions that will most likely not be resolved in my lifetime, if ever. However, it was worth every minute of study to get a glimpse into the abyss.
 
Last edited:
Ivan Seeking said:
I wasn't suggesting that we adopt a new worldview, I was just asking about the state of the problem and opinions. In the end I found that wrt the measurement problem, for example, there was no consensus, which may be why many scientists resist any discussion.

I suspect it's related to the fact that the proposed solutions are largely untestable. It would perhaps be more a reason for concern if scientists had reached a consensus on this issue. As an astronomer, I would tend to avoid some of the more important questions as well (such as the ultimate fate of the universe, what happened before inflation, etc.) simply because they are too far beyond our grasp at the moment -- I don't trust our current models to be able to answer them. I think it's a credit to the training scientists receive that they don't feel the need to always have immediate answers to sweeping questions.
 
No experimental test? Then it's not (yet) physics

ditto SpaceTiger, and good point. Part of sound scientific judgement involves "judging the moment" and "choosing your struggles wisely". I might mention "analog gravity" as something extremely novel which nonetheless seems to me within reach for young researchers just starting out, and which would be very important if its predictions can be experimentally confirmed.
 
Last edited:
Yep. What interested me most were questions that don't generate grant money or careers.

However, this doesn't mean that those questions should be ignored or forgotten. And I think it is true that orthodoxy can stifle valid discussions of the deepest issues. I once had a physics professor close her door so that she could freely discuss her views on such matters, and I was quite struck by this.
 
Ivan Seeking said:
Yep. What interested me most were questions that don't generate grant money or careers.

However, this doesn't mean that those questions should be ignored or forgotten.

For questions that are purely philosophical, it's not clear that the scientific community should even be involved. Questions that are just way out of the reach of current theory, on the other hand, may turn out to be trivial or irrelevant in the later stages of scientific development. I think there's an understandable level of suspicion towards scientists who put too much weight on these broad questions that have religious or philosophical implications. These people often have a lot of baggage that can skew their judgement on issues worthy of actual scientific investigation. An example that comes to mind is the steady state universe/big bang debate, in which certain followers of the former continued their crusade well after the majority of the scientific community had been convinced of the latter. I can only speculate as to their actual motivations, but I can say we don't see such passionate resistance to theories of stellar evolution or orbital dynamics,

The questions shouldn't be completely ignored, of course, but I think it's understandable that they're often avoided. We can't disprove the MWI (just for example), so it shouldn't be treated as false, but on the other hand, it's not clear that an extended public debate (within the scientific community, I mean) would be productive.
 
Last edited:
Chris, Vanesch and ST, I find this all very enlightening.

What do you think of Max Tegmark at MIT?

Are multiverse theories testable?
Is it all just philosophy?
On Nov 3, 2003, at 14:38, Walter H.G. Lewin wrote:
Q: Is there a way, at least in principle, that the existence of multiple universes as described by you in Sci Am, can be experimentally verified or falsified? If not, as several of my colleagues have pointed out, it falls in the realm of religion and philosophy, but not physics.
A: Absolutely! The key point, which I emphasize in that article, is that a fundamental physical theory can be testable and falsifiable even if it contains certain entities that you cannot observe. To be testable and falsifiable, it merely nees to predict at least one thing that we can observe. A good example is the theory of eternal inflation, where our Hubble volume constitutes only an infinitesimal fraction of all space. Since this theory makes the firm prediction that Omega = 1 to an accuracy of order 10^{-5}, this model (and all those level I parallel universes with it) would have been ruled out if we had measured say Omega=0.70+0.02. Instead, our latest constraints in astro-ph/0310723 are Omega=1.01+-0.02.

http://space.mit.edu/home/tegmark/

Sorry, this is the watered down layman's discussion, which is all that I can understand.

Of course a lot of this is old, from when I first became interested in MWI, but that was when String Theory was going strong as well. I'd like to hear your opinions on where we've come in the last 4 years on MWI. Has interest in it dwindled as it seems to have with String? Or am I misunderstanding where String Theory is going? The interest in quantum computing is picking up, and it ties in strongly with MWI, doesn't it? Having the opportunity to learn from you guys is awesome.
 
Last edited:
Evo, he's referring to a different multiverse theory. Notice he uses the phrase "level I parallel universes", referring to an open multiverse predicted by inflation. The MWI is actually a level 3 multiverse by his classification and would not be testable by the methods he's referring to.
 
SpaceTiger said:
Evo, he's referring to a different multiverse theory. Notice he uses the phrase "level I parallel universes", referring to an open multiverse predicted by inflation. The MWI is actually a level 3 multiverse by his classification and would not be testable by the methods he's referring to.
Yes, that's correct he does say Level III is not testable.

So, is MWI at Level III and IV? Ah, it's levels II-IV?

Remember, I am at the Scientific American level of understanding, be kind.
 
Last edited:
Evo said:
Yes, that's correct he does say Level III is not testable.

So, is MWI at Level III and IV?

I think he puts it at level III, but I haven't read the paper. Max gets away with this cause he does a lot of useful stuff too. :wink:
 

Similar threads

Graduate Parallel Universes: The Mind-Boggling Reality Confirmed by Oxford Scientists
  • SF
  • · Replies 6 ·
  • Astronomy, Astrophysics, Cosmology
Replies
6