9.6 KiB
[D] Can a super-villain with a planet buster coupled to a quantum measurement, eliminate (observable) histories in which he loses?
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Author: u/VanPeer The shard made me do it*
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URL: https://www.reddit.com/r/rational/comments/7gwhf0/d_can_a_supervillain_with_a_planet_buster_coupled/
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Score: 7
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Created: 2017-12-01T17:22:56
Post:
http://www.anthropic-principle.com/preprints/manyworlds.html
Sort of like Worm!Coil but constrained by known physics & assuming MWI is true. I am unclear exactly what causes timelines to split i.e what constitutes a quantum measurement. The link above claims any thermodynamic irreversible process will causes a split. Is this accurate? I need help in thinking through scenarios where a super-villain can exploit that.
Comments:
u/NebulousASK [+17] (5 minutes later)
I am unclear exactly what causes timelines to split i.e what constitutes a quantum measurement.
You and everyone in physics. But at the level you're talking about, there are a ridiculous number universe-splitting events on Earth alone at pretty much every conceivable moment.
If all the villain wants to do is create a dichotomy - every reality is either his, or Earth-free - he doesn't need any special quantum technology to do this. He makes his attempt, and in any universe where he is defeated, he activates his device.
u/ArgentStonecutter [+17] Emergency Mustelid Hologram (4 hours later)
He makes his attempt, and in any universe where he is defeated, he activates his device.
There's a short story where a group of scientists have been trying to build a new high energy particle accelerator and it never seems to be able to get up to full power. They realize that if it did, it would collapse the false vacuum, and so the only surviving world-lines are the ones where something went wrong.
u/Penumbra_Penguin [+3] (a day later)
I don't suppose you have a link? This is difficult to google.
u/ArgentStonecutter [+4] Emergency Mustelid Hologram (a day later)
Afraid not, I don't even recall the author.
u/DangerouslyUnstable [+2] (5 days later)
Ugh now that you've said it I remember reading it, but am also completely unable to find it. This is going to bug me.
u/VanPeer [+2] The shard made me do it (59 minutes later)
Yes, universe splitting would be mindbogglingly prolific. Oh... that would render the quantum measurement superfluous wouldn't it. That's what I was afraid of.
Will sub-atomic irreversibility & consequent universe-splits cause all physically possible events to occur? This seems to be taken for granted in sci-fi but it is not at all obvious to me that would appreciably affect macroscale evnts that we care about. Comments?
u/NebulousASK [+6] (2 hours later)
I share your skepticism. The truth is the many macro-scale events have very little, if any, quantum variability. The specifics of the electron collisions in your brain aren't usually going to change the decisions you make, for example. Every world that splits from the same initial gunshot is going to have the same resulting bullet hit.
u/ArgentStonecutter [+11] Emergency Mustelid Hologram (4 hours later)
The specifics of the electron collisions in your brain aren't usually going to change the decisions you make, for example.
The quantum events that change your decisions now would be ones that happened minutes, hours, days, or years before, and the changes only butterflied out to the macro scale over time.
But there would still be many events in the brain of every person, every second, that would eventually result in macroscale differences. And it doesn't matter whether these events happened in the past or are happening now, because until they've amplified to the macroscale level every version of you will still be making the same macro decisions, so you can still usefully think about them as if they were happening now.
u/VanPeer [+2] The shard made me do it (2 days later)
Thanks! Do all quantum events eventually cause macro-scale deviations? Specific cases such as the double-slit experiment or a Geiger counter is clear enough.
u/ArgentStonecutter [+2] Emergency Mustelid Hologram (2 days later)
If they don't, can they be said to have happened?
u/ajuc [+3] (a day later)
Every world that splits from the same initial gunshot is going to have the same resulting bullet hit.
I think there's very small amount of worlds where the bullet would spontanously disappear, or quantum-tunnel through?
u/None [+3] (a day later)
There are, but the failure rate of any machine you build to implement the universe destroying will be far worse than the incidence of this (in no small part due to its own parts quantum tunneling away)
u/NebulousASK [+2] (2 days later)
Maybe? I suspect not.
u/ajuc [+1] (2 days later)
Why not? If you accept that universe splits according to probability, then why cut off very improbable events? There should be a continuum of universes created at every quantum interaction.
u/NebulousASK [+1] (2 days later)
I suspect in the macro-case there are hard limits that make something like tunneling of an entire bullet not only improbable but physically impossible, even at the quantum level.
Quantum uncertainty doesn't eliminate physical constraints; it just provides wiggle room at the edges, allowing some events to violate certain classical assumptions. But the wavelength of a bullet is smaller than the size of the bullet; the envelope will not actually extend the width of a human body. I suspect there are some asymptotic probability considerations that actually do reduce to zero past a certain spacetime interval.
u/ajuc [+1] (2 days later)
Asymptotic by definition would never reduce the probability to zero, but I get your point.
u/NebulousASK [+1] (a day later)
I don't think so, but I'm not sure.
u/ArgentStonecutter [+6] Emergency Mustelid Hologram (an hour later)
Controlling the pruning of branches is basically the gimmick in Greg Egan's first novel, Quarantine. Any more details would be spoilers.
u/traverseda [+2] With dread but cautious optimism (3 hours later)
http://pruninganinfinitetree.com/Pruning%20an%20Infinite%20Tree%20Chapter%201.html
u/DCarrier [+1] (5 days later)
The problem is that there are universes where he never existed and universes where he existed but never built that device. Those universes will have proportionately higher probability density as he destroys universes where he did build the device.
I am unclear exactly what causes timelines to split i.e what constitutes a quantum measurement.
It's less like a tree and more like a ripple. If you had rocks and areas where waves went slower and that sort of thing in a pond, then when you make a ripple you can see it split into different paths, but that's just an approximation, and it's really going along every path continuously. Likewise, the universes aren't discrete. It's just a single waveform moving through world-space.
u/VanPeer [+1] The shard made me do it (8 days later)
What does it mean to say the universes aren't discrete, though? There are two discrete versions of an observer, one where he observes the photon take the left slit & one where he observes it go through the right slit. Honest question. Thanks
u/DCarrier [+1] (8 days later)
Since the photon and the rest of the universe are independent (at least within the subset of the multiverse where that experiment is being performed), you can decompose it into the component for that photon and the component for anything else. The probability of finding the universe in a particular state is just the probability of finding the rest of the universe in that state times the probability of finding the photon in that state.
And for the photon, it's just like a ripple. It gets emitted and there's a continuum of possibilities where the photon heads in every direction and starting at every time. Most of the waveform gets blocked by walls, except for the two slits. The probability of a photon being just past the wall and not near the slits isn't zero, but it's pretty unlikely, so it's easier to think of what happens after as two separate ripples, even though really it's just two parts of the same ripple. From there they spread out and start to interfere with each other, and you end up with an interference pattern where parts of the far wall have bigger waves hitting them and parts are still. You can think of it as different histories diverging and then coming back to the same universe and interfering with each other, but it's not like there's discrete histories. It's all one giant ripple.
u/VanPeer [+1] The shard made me do it (9 days later)
Thanks for taking time to reply. Am I correct in interpreting your explanation as being consistent with the Copenhagen interpretation and not the MWI? i.e. in your above version observations cause a collapse of the wave function, unlike Many Worlds where each is a discrete history. I'm not trying to argue, just keeping things straight from a phyiscs & fiction POV. Thanks
u/DCarrier [+1] (9 days later)
I was describing Many Worlds. Copenhagen is that, plus when too many particles get entangled the universe just randomly picks one and says "let's go with this".