Anna,

There is an ongoing discussion over on the google Everything list
about Quantum Suicide, which is nearly equivalent to a coin toss.

QS is proposed as a test of MWI- the Many World Interpretation of quantum
mechanics. In QS it depends essentially on a coin toss if an experimenter
is either killed or survives in each of two worlds created by the coin
toss. Anna's post below indicates that coin tosses are quantum events.

A witness accompanies the experimenter. There is with each experiment a
50-50 chance of survival. The question is if this is a valid test of MWI?

It turns out that the only way that MWI can work and predict known
experimental results is if the measures of the various experiments known to
the experimenter and the witness ahead of time are equivalent to the
probability of each new parallel world created by a great number of
experiments.

If the MWI measures predicted by both the experimenter and the witness are
equal to the collapse wave interpretation, then MWI is just another
interpretation with no chance of distinguishing one interpretation from
another experimentally. That is the standard perspective.

I disagree and maintain that after 2 million experiments: in which the
experimenter and a witness survive in one world; and another witness and a
dead experimenter are created in a "created" orthogonal world; the
surviving experimenter and witness in the final experiment would know to 5
sigma that MWI was/is correct.

But that is a tiny number compared to the 2 million witnesses that do not
have that information at the 5 sigma level and would have a minuscule
effect on belief thru-out the multiverse.

However, if the experiments were to continue another 2 million times, then
2 million new witnesses would know that MWI is correct at the 5 sigma level.
So by then half of the multiverse knows MWI is correct.

That is, at that point in time, there are 2 million
parallel/orthogonal worlds where the witness cannot distinguish MWI from
collapse theory at the 5 sigma level. But after 4 million experiments there
are an equal number of witnesses along with a dead experimenter in 2
million worlds where the witness can distinguish MWI from collapse at the 5
sigma level. Eventually with continued experiments, most of the multiverse
will believe in MWI.
If that does not make sense, you are not alone.
Richard


On Tue, Jan 8, 2013 at 1:47 AM, Anna <panth...@mail.com> wrote:

> **
>
>
>  Humble coin toss thrust to heart of multiverse debate
>
>    - 02 January 2013 by *Jacob 
> Aron*<http://www.newscientist.com/search?rbauthors=Jacob+Aron>
>    - Magazine issue 2898 <http://www.newscientist.com/issue/2898>. *Subscribe
>    and 
> save*<http://subscribe.newscientist.com/bundles.aspx?prom=6005&intcmp=SUBS-nsarttop&promcode=6005>
>    - For similar stories, visit the 
> *Cosmology*<http://www.newscientist.com/topic/cosmology>Topic Guide
>
> WHY is there a 1 in 2 chance of getting a tail when you flip a coin? It
> may seem like a simple question, but the humble coin toss is now at the
> heart of a lively row about the multiverse. At stake is the ability to
> calculate which, of an infinite number of parallel universes, is the one
> that we inhabit.
>
> The debate comes in the wake of a paper posted online a couple of weeks
> ago by cosmologists Andreas Albrecht <http://albrecht.ucdavis.edu/> and
> Daniel Phillips, both at the University of California, Davis. They argue
> that conventional probability theory, the tool we all use to quantify
> uncertainty in the real world, has no basis in reality (
> arxiv.org/abs/1212.0953). Instead, all problems in probability are
> ultimately about quantum mechanics. "Every single time we use probability
> successfully, that use actually comes from quantum mechanics," says
> Albrecht.
>
> This controversial claim traces back to the uncertainty principle, which
> says that it is impossible to know both a quantum particle's exact position
> and its momentum.
>
> Albrecht and Phillips think particle collisions within gases and liquids
> amplify this uncertainty to the scale of everyday objects. This, they say,
> is what drives all events, including the outcome of a coin toss.
> Conventional probability - which says the outcome simply arises from two
> equally likely possibilities - is just a useful proxy for measuring the
> underlying quantum uncertainties.
>
> In the case of a coin toss, quantum uncertainty in the position of
> neurotransmitter molecules in the nervous system of a coin flipper might
> translate into an uncertainty in the number of times a coin turns in the
> air before being caught, ultimately determining whether it is a head or a
> tail, the pair suggest.
>
> In a back-of-the-envelope calculation that used estimates for coin size,
> speed and neurotransmitter uncertainty, the pair were able to show that
> this quantum sequence of events could give the same probability of throwing
> a head or a tail as the conventional calculation - one-half. They say this
> supports their argument that conventional probability is just shorthand for
> an underlying quantum reality.
>
> But does any of this matter if the odds are ultimately the same? Yes, says
> Albrecht, because there is one use of conventional probability that cannot
> be traced back to a quantum origin: predicting the fate of the universe.
>
> Physicists have long known how to make predictions about quantum objects,
> even though such entities do not have fixed properties until they are
> observed. Before that, they exist in a superposition of all possible
> states, which is described by an equation known as the wave function. A
> principle called the Born rule lets physicists extract a probability of
> observing a particular state from the wave function, and so allows them to
> predict a quantum object's behaviour.
>
> There is just one problem. The Born rule breaks down in some situations.
> The latest theories in cosmology say that our universe is just one part of
> a vast multiverse containing a large or even infinite number of other
> "pocket" universes. Some of those universes will be exact copies of our
> own, right down to a duplicate you. The mathematics behind the Born rule
> can't cope with this.
>
> "In these situations, the quantum wave function can tell you nothing about
> which pocket you are in," says Albrecht. That's a problem if we want to
> predict the properties of our universe, which will look identical to many
> others at a given point in time, but which can eventually evolve
> differently due to quantum uncertainty.
>
> Until now, physicists seeking to predict the properties and behaviour of
> the multiverse have added a sprinkling of conventional probability to
> reflect the chance of us being in a particular universe. For example, in a
> multiverse with just two universes, you might add a 50-50 chance of being
> in either one, just as we instinctively assign the same odds to a coin toss.
>
> Albrecht says that is wrong. Unlike a coin toss, these probabilities do
> not have a quantum origin. To explain the multiverse scenario, a new theory
> of probability is required. "It is not an extension of our everyday
> experience of probability," he says. "It is really a brand new thing."
>
> The claim has sparked a range of responses from cosmology heavyweights. Mark
> Srednicki <http://web.physics.ucsb.edu/~mark/> of the University of
> California, Santa Barbara, is waiting for the idea to be fleshed out. "To
> make it really interesting, you have to go to the next step and say what
> the new method is going to be," he says.
>
> Don Page <http://www.physics.ualberta.ca/Faculty/DonPage> of the
> University of Alberta, Canada, who was first to highlight the problem of
> applying the Born rule to the multiverse, says researchers are already in a
> pickle. "If the Born rule doesn't work, we need a replacement, but we can't
> deduce one from concepts we already have."
>
> Alexander Vilenkin <http://cosmos2.phy.tufts.edu/vilenkin.html> of Tufts
> University in Medford, Massachusetts, doubts there is a replacement. "If
> you know the wave function of the universe, you still have to decide which
> copy is you," he says. "I think there is no way to do it." As a result, he
> is sanguine about continuing with conventional probability in multiverse
> calculations.
>
> Albrecht admits that a single example of a system that can be described in
> purely conventional terms would lend support to this argument, but he says
> he hasn't encountered one yet. "I've been challenging people for a couple
> of years now," he says.
>
> One that comes close is placing a bet on the value of the millionth digit
> of pi. It is easy to calculate this exactly - it is 5, as it happens - but
> if neither party knows that in advance, it becomes a probability problem,
> and conventional probability says there is a 1 in 10 chance of winning the
> bet.
>
> Albrecht and Phillips say quantum effects come into play here too, through
> the choice of which digit to bet on, either as neural fluctuations, as with
> the coin flip, or as other uncertainty from a random number generator.
>
> Page thinks that is a claim too far, though. "One could conceptually
> imagine a case where quantum mechanics is not relevant for choosing which
> digit we are talking about."
>
> Our understanding of the multiverse is far from settled, says Srednicki.
> "The multiverse is an unruly beast and we would like to tame it, but I
> don't think anyone has drawn blood yet."
>  [image: Issue 2898 of New Scientist 
> magazine]<http://www.newscientist.com/issue/2898>
>
>    [image: The penny has dropped <i>(Image: Nick Veasey/Getty Images)</i>]
>
>    The penny has dropped *(Image: Nick Veasey/Getty *
>    - From issue 2898 <http://www.newscientist.com/issue/2898> of New
>    Scientist magazine, page 8-9.
>
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