55 | A Conversation with Rob Reid on Quantum Mechanics and Many Worlds 

I will never get tired of this particular discussion topic.

Rob is such a great speaker. Very articulate. It's always a great show when you have two great speakers on a podcast. Bravo!

I'm very grateful to have evolved along the same branch of the wavefunction of the universe as this version of Sean Carroll.

30:09 like a photo of a flying baseball. If it’s clear, you can tell the position but not velocity or trajectory. If it’s blurry, you could tell the trajectory and velocity, but its position is uncertain. You’re welcome for this analogy. Love your work Sean!!

Rob is a great podcast host and Sean Carrol is one of the best physics communicators. What a show. Thoroughly enlightening. Need more programs covering other topics of interest like time or cosmology etc involving Sean and Rob together in a podcast!

I like this style of Mindscape more and the interaction between the two of you makes it much easier to take in the information.

Has Sean ever spoken about the delayed-choice quantum eraser experiment? I would like to hear him dig into what it is (or isn't) and how that behavior is described by different QM interpretations? Reading about the experiment makes it sound incredibly significant, but it seems to never be referenced as an addendum to the vanilla double-slit experiment when speaking about topics of decoherence, entanglement, and how they relate to information -- making me think I must be misconstruing some basic QM principles.

Every time I take in a discussion like this, I find questions and/or answers to old ones. Without actually being a student Im starting to get the maths under some growing bit. I notice that hearing someone at this level express some idea I have toyed with is both exhilarating and humbling. Refining the whole mess is great fun. So long as I dont fall through some wrong looking glass . . . for too long. Thank You Both.

Niven, Larry; "For a Foggy Night," 1971 (...and, thank you Sean (and Rob)! Excellent work as usual :)

I still don't understand the probability issue. You observe an electron that is 10% up and 90% down. The universe splits in 2 and now one version of you sees it up and another version of you sees it as down. So as Sean points out, both results occur with 100% probability. If we want some frequentist approach to probability, in 50% of worlds it was up and in 50% it was down, so that doesn't give us the 10/90 split either. Where does that come from? Sean talks about the "thickness" of the slice, but what is that thickness meant to represent? It seems to be something added to the model: the physics of QM includes the amplitude for the electron to be spin up or spin down, so that number must represent something. So we just put that in. But it doesn't seem to be following from this many worlds picture. Had it been that case that there were 9 worlds in which it is up and 1 in which it's down, that would be a beautiful mechanism for giving us the probabilities, but that doesn't seem to be the case. Instead we're left with the fact that the probabilities work out in a certain way, but without any clear mechanism (at least as explained by Sean here, I have seen some more in depth explanations by him elsewhere, but they didn't make that mechanism clear to me either). He gives the analogy of a loaf of bread. You cut it into two unequal slices, so of course the probability that any atom will end up in one slice or the other can be unequal. But why? Because there are more atoms in one slice than the other! But there aren't more worlds in which the electron is spin down than spin up. So, again, _how_ does the "thickness" of the slice lead to us measuring the probability differently? It's certainly true that we _do_ measure the probabilities as given by the born rule. But many worlds doesn't seem to make any sense of that rule.

I keep coming back to this episode of Mindscape.

Reid is a marvelous interviewer.

I'm confused by this: How do we know practically, not philosophically, what counts as measurement? In the double slit experiment I get it that the Schrodinger equation makes the photon interfere with itself. What equation says that when I put a film grain or a CMOS pixel somewhere in the wave function the photon will interact with it in a discrete way rather than put the detector in superposition? What if I want superpositions? I've seen many lectures that say "if you do a measurement you get a probability that's the square of the wave function blah blah". Does the cookbook or Copenhagen approach to quantum mechanics actually tell you a priori when you'll get superpositions and when probabilities? Or is there an empirical body of knowledge that says things like chemistry or microelectronics or neurons count as measurements, free-flying particles are superpositions, and if you want a bunch of atoms in superposition you have to do weird supercooled stuff? Even in practical terms that expectation seems ill defined.

Now for something completely different. Rob has a new, last thirty days, Ted Talk on Synthetic Biology and its risks. Worthwhile.

Sean's podcast is of such high quality content and speakers it will have 1 mil subscribers before we know it. I congratulate Sean in advance !!! Bravo!!!!!

Amazing talk. If Sean would try DMT,I think he could master the universe and conciousness. Great to hear this explained in 3dimensional logic. Still working hard to grasp the reality logic lol

Starting at around 36:28 is the money shot in Quantum Mechanics for me, it's like when I read Brian Greene's book The Elegant Universe, there was a money shot of a clear understanding of space-time in that book, and in this podcast there is a clear understanding of superposition and the many worlds interpretation.

The trouble with announcing at the beginning of an interview that you've prepped prior to the interview with the person interviewing you is that it casts doubt on the idea that the interviewer "stumbled upon" an extremely relevant point.

A great discussion of one of sciences' great shames. Never should you stop asking questions.

Thank you, Sean! Question for you... given the fact that the last time I had a physics class was in high school back in 1991, if I wanted to pick up a book or two or perhap even a take course (today) to better understand the many points made in this podcast, what would you recommend?

Brian Greene and Sean Carroll are my two favorite physicists to listen to and learn from.

So can I use a quantum random number generator to play the lottery, thus knowing I will live in a world where I am guaranteed to win?

New podcast.... it's a good day🤙

Sean speaks so well.

.."if you have two electrons, you don't have two clouds". What if you have two observers? If you and Rob both look at the moon are you seeing two moons? Are you creating two distinct collapses of the same field? We can only ever experience our own collapsing wave, and yet it appears we are seeing the same seperate object?

Good one... I'm not a physicist but I loved physics in high school and college and with my background I'm not a professional like Sean, but I'm also not uneducated (I've read numerous books on Quantum physics and 'Quantum Reality'): I'd like to add to what Sean says, but as he indicates if I felt I wanted to comment on the subject matter I can always create my own Podcast. Sean is not interested in my opinion, he gives us his professional opinion, but commentators here have to do their own work to pitch their ideas. With that in mind I would like to pitch my further ideas on the subject to the folks who read these comments: In the book titled "Quantum Reality" 11 different explanations for the reality of quantum physics are presented. I like two of those presented alternatives, and I think these are ones that Sean could also mention: Theory 8: We don't know enough yet and when further things are discovered an explanation of Quantum Reality that people find acceptable may be formed. Theory 11: There is no deep reality. Theory 11 is my favorite. Theory 8 is satisfying because we all can just relax, not worry about the implications of Quantum Theory, and we can hope that at some time in the future, with more information, things will be understood, and hopefully something will make sense. Or alternatively we at least will have proof about the nature of reality. When you accept Theory 11, that there is no deep reality... you do not 'split' the Universe trillions of times a second everywhere... instead, give up. There is no reality. Stop trying to make sense of Quantum field theory. Why assume that things should make sense. We live in the macro world where Newtonian Physics seems to apply and our brains have a 'common sense' component evolved only to deal with this world of our experiences. -------------------------- Summary: I use Theory 11, there is no deep reality. There's no realness of anything at the quantum level other than the equations. Whenever Sean yet again splits the Universe I just think to myself, nope, none of that is necessary. You can just stop trying to make sense of it. Just use the math and say there is no way to interpret the math that is real to us. Cheers!

I have questions : Which particles or waves have been observed capable of entanglement? What is the present practical means of establishing entanglement? In many worlds, aren't all other worlds except this one that I am aware of irrelevant and infinitely unobservable therefore their existence can only be relegated to faith, and what occurs in this world is completely random because I can never be aware of its consequence?

Now I need to go rest in a darkened room !

At what point does matter have a wave function ? I’ve heard of scientists using macro sized molecules to perform the double slit experiment , why does it become harder to perform the experiment with larger objects? and if it was possible to propel large object like a tennis ball and it had a superposition would this make it possible to teleport it through space ?

Great talk 🙂. My question: Does many world's indicate we don't need to worry about the Higgs vacuum collapse? Following the quantum suicide logic: since there is always a universe where the vacuum doesn't collapse we will always have a conscious experience of the metastable vacuum. Also, does the vacuum collapse give the universal wave function a way to recycle/erase universes and free up Minkowsky space.

On the subject of the Double-Slit Experiment...I am yet to learn of a mechanism of "detecting" which slit a photon passes through without destroying the "original" photon; or, in the case of an electron, without interacting with it (and therefor fundamentally changing its future). I'm not disputing the evidence, I'm uncertain about the interpretation

It is breaking my heart to know that future history will show that in this place and time, there were fewer then 100 people taking quantum physics seriously. And that they kept it secret from one another for fear of prosecution in the year 2020.

Lol I love the coffee only exists in one cup analogy

+Sean Carroll Is it possible that the efficiency argument against reality being a simulation is solved by the observation phenomenon (observing a particle causes it's position to be actualized) in quantum physics? The efficiency argument is that a true simulation would only simulate parts of reality at a time when it was within a player character's visual reference frame. Many computer game simulations use this tactic to allow for creating massive game worlds without running out of pc resources. Could this observation effect be a way of creating efficiency in the system and thus lend more credence to the simulation argument?

i have been listening since you was last on joe rogan, thank you sean

If each of us in essence "splits" roughly 5000 times per second based upon radioactive decay in our bodies and there were roughly 5178 seconds in this podcast (3600 + 1560 + 18) then if I did the math right (and someone please double check me as I could have screwed up) there should be 5000 to the power of 5178 more Sean's at the end of the podcast then at the beginning, which is a number that is over 19000 digits long! That my friend is a BIG number. This whole multi-world thing kind of reminds me of "snapshots" that some journaling filesystems make. Appreciate the mind expanding conversations!

"How many of you are there?" Depends on how many times the multiverse has branched.

Love this topic

Very interesting, thanks.

OH MU MAMA! Excellent.

Excellent conversation. I do wonder about the conflation of the wave function with the underlining physical reality. The wave function of an electron is not an electron. It is a description of the probabilities that an electron is in one state or another. That is not the same as being an electron. It's like the difference between epistemology and ontology. Sean kept talking about there's only the wave function that's like saying there's only a map of Paris.

After listening to this I was wondering how you prove it? Sorry but I'm a kind of observation/experimental person.

Neither speaker goes 'aah' or 'umm'. That's really hard!

I love Quantum Mechanics

If spacetime can bend, could it also spin. Could a blackhole cause space time around it to spin and in doing so have the appearance from observers in a seperate galaxy that matter orbiting the blackhole such as a galaxy, is orbiting the blackhole too fast compare to the gravity holding the rotation together.. Another question is how does the gravity gradient as you move further away from the event horizon affect the flow of time in that space. Does time speed up in regions further out compare to regions closer to the event horizon? And how does that affect the observations made by us observing from our galaxy, or is it negligible?

This podcast is a real sleeper. I suspect it will be huge one day. As of now it's 18 July 2019 he's at 38k subs. Let's see where he's at in 2 years.

Rob wrote an interesting novel called _Year One_ . I read it about 8 years ago when it came out. He is an interesting person and a talented writer.

A complete guide of quantum mechanics

Let’s say you have two possible locations for an electron, one more probable than the other?? My question is what makes for the difference in probability?? There must be some underlying principle determining the difference in probability?? If the electron is potentially everywhere, but is constrained by probability to a range of locales, then what causes such a range of probability values?? I suppose the real question is what makes for the difference between consistent and decoherent histories??? The macroscopic world obeys certain laws and principles, if such a macro world is emergent from a more fundamental quantum reality, then by extrapolation downward in scale, could the rules of the quantum world also be emergent from a still more fundamental underlying reality?? If so, what would that reality be??

Interesting

I definetly felt myself in superposition few times in my life when i was younger and loved experimenting

I'll listen to the podcast Sean, but I still don't understand the principle of Everett's interpretation, as I'm sure you'll talk about it in that podcast For me, parallel universe is indeed parallel, and if you take a choice or action, in the several other worls where you exist at the same point of space and time you'd take the same action, as for a quantum effect which would in theory take the same action in all worlds. I'm not sure I'm being very clear, but I think parallel means parallel

I still cant get around what I hear... could you discuss how the "language" of mathematics describes the quantum world? Low brow science ex. I have "one" rock I throw it over my shoulder I have "zero" rocks... it seems all of our observations come in mathematical descriptions and try to put them into everyday language... is there a disconnect from ones and zeros and decimals to "hey there that's the electron" I mean it's a wave function yet a cloud chamber you see "one" trail made by "one" electron? I have no idea what I'm talking about now so someone pls elaborate lol

Many Worlds still doesn't help us understand anything about where the randomness of events comes from?

Apart from the circular answer that QM says you can't know position and momentum. Why can't you or why is QM the way it is. Is there a deeper answer or is this the bottom of reality.

Is quantum many worlds interpretation useful in measuring the thickness of Big Bang probabilities? Could the collapse of the wave function be the precursor to the event that started the Big Bang? Also your example of the coffee going through the table wasn’t to off the wall to be considered weird if that probability was the example of the coffee becoming a superfluid, albeit it is strange if that were to occur without an external input.

In the many worlds concept, who and what action is required to create another version of the observer and thereby another world (let's call this cloning)? In other words, is it only the observer of an electron who gets cloned, or does that individual's observation of said electron also trigger a cloning of everyone else in the world? Does the cloning only happen when an electron is observed at the quantum level, or does it happen the minute we observe anything that is comprised of electrons even at the non-quantum scale (like a traffic light changing)?

So do the lives of animals also branch off into many worlds?

I agree with Sean’s interpretation, but not exactly in the way explained. ‘Splitting’ is a way of thinking of it, but that assumes time is something real. I’m thinking the universe somehow exists without time, in a way that all possible results are occurring without the concept of a clock ticking. What we experience as time is what I have no idea about. Is humanity’s inability of thinking without a concept of time making the question fundamentally impossible to understand. So I propose the seemingly simple question; What is Time? Everything will follow if this is answered; at least in my ignorant, fuzzy frustrated curiosity. Infinities, path integration, wave functions all go away or make sense when energy isn’t experiencing time, but is still somehow evolving. Sorry I can’t make the thought more clear, it’s because I don’t understand it.

About quantum mechanics, looking at normal mechanics, for events to happen they need time and space. Within time and space then, matter follows the laws of physics, as far as i know all of which are variations of the principle of the action of least energy. In any case, the question arises still, what executes or implements or enforces or gives rise to the laws that events must follow? Or like in a computer it would be a cpu executing instructions. What is this 'processor' and can we ever discover it? Quantum mechanics follows some laws of probability, but what mechanism gives rise to that probability is obviously the question. I am just adding further as above, the question of what would be the thing that then causes that mechanism, if any, to have authority? Or in short, what about the universe decides the outcomes of events or calculates the outcomes of the laws of physics?

I think this is a mistake of assuming a good model must tells us something fundamental about reality in addition to being predictive.

Imagine those universes where non tunneling, with all objects, appears as improbable as tunneling in this one.

Let’s say you’re in a home in Los Angeles, but there is a world where you are in a home in New York?? Now, what makes being in a home in New York more decoherent than being a step away to the right from where you are?? Is it because you are entangled with your environment in your home in Los Angeles?? If so, then the pivotal factor in determining decoherence and consistency is you?? Your awareness?? Your entangled state??

I have no idea why are people confused with Heisenberg's principle and position/velocity debacle. Take a 1/1000000th second exposure photo of a car. You know perfectly where it is, but you have no idea how it's moving. Now take a 1s exposure photo of a car. You know the speed, but you can't tell where exactly it was during that second, because it wasn't in one spot at the same time. And it isn't just measurement. Without time, velocity simply doesn't make sense. And with time, a position of a moving object doesn't make sense. That's why velocity and position can't really "exist" together.

To completely flip this Rob should have done the introduction.

Thank you for this fascinating talk. I have a naive question for you. My brain, as yours and any, is made from particules and essentially works by sending an electric signal from one neuron to another through synapses (which you can show on a EEG for instance). That's roughly the way thoughts and ideas are generated. I guess we can thus assume a brain constantly collapses wave functions by locating an electron in a certain region and in some sense an idea would be the result of a measurement. Now imagine I consciously order my brain to generate a number between 0 and the infinite, so that I have an infinite liberty to choose this number. According to the many worlds theory, at the moment I'll write this number, I should create a branch, is that true ? If so, what would be the probability, or thickness, of a branch in this case ? One over an infinity, meaning 0, so none of these branches should exist. Isn't that paradoxical ?

If some binary event has a 99% (A outcome) vs 1% (B outcome) probability, why isn't it proposed that the universe splits N times, where 99% of N has A outcome?

My latest scary conspiracy theory is that Dark Matter could be an advanced form of an AGI spread over the observable Universe that evolved itself to not being easily interacted with even if detectable by gravity discrepancies...we are being watched...xD

It is sad to think about all the different branches where I don't/didn't listen to this episode.

I am pretty sure this question has been answered since the many worlds theory is of interest to the quantum information community but why doesn't the no-cloning theorem prevent exact duplicates (clones) of someone when branching occurs? More importantly (and I suspect Avi Loeb might have missed this in the podcast on Oumaumau) in 1962 papa Oommaumau (mow, at times)) was observed by many in the United States and elsewhere.

"To let understanding stop at what cannot be understood is a high attainment." That was a quote in a book I read as a teenager. At the time it seemed profound, later it seemed like giving up, after all how can you know what can and what can not be understood? All you can do is try to understand or give up. Now I am not so sure. When (if ever) we get to the final theory of everything will that be the end to all interpretation? Or will keep trying to understand why it is? Why is that the final theory? Ultimately there is no reason why, the universe just is. Do we have to wait until the final theory of everything to reach that conclusion? Even with the final theory, we won't have figured out the complex stuff, the various levels and layers of interactions. But we could use the final theory to figure them out. In other words, we could shut up about what it all means, and just calculate what it is.

They finish each others sentences.

I like your lectures and I like the fact you have the power to tell the world that are Top people Are told not to pursue quantum reality which clearly holds the key to life. We seem to push a lot of money into Cern which has produced and sloved a few issues , but now seems underpowered to move forward now. I dont profess to understanding all I have read on quantum messurement as I understand the differance views but its impact on everyday life is the hard part.

Anyone have a link to the other guy's podcast?

The "missing mass" of our Universe is just the infinitesimal weight of all those bad life decisions adding up across gazillions of split other universes.

"And when they were only half way up, there were.. " 37:31

I don't believe in the many worlds view of quantum mechanics. My arguments is simply this: is there any way one can conceive of a universe in which Amber Heard is actually truthful? I rest my case.

Thumbs up if you are in the "Snap once" universe

Would entropy exist in the quantum level?

what i learned thus far: unlike socrates, einstein was no gadfly....;

Starting this podcast at any random time, a wavefunction collapses and with a certain probability you will find the interviewer being interviewed by the interviewee, or vice versa.

You should also do a podcast with John Michael Godier of Event Horizon channel.

This podcast seemed geared for much of Rob's audience and less so for Sean's community. To me, it covered too much prior Mindscape ground. The Sean-David Alpert discussion was more stimulating, at least, again for me, but that overlap was mentioned at the get-go. However, pilot wave thinking is for me.

William of Ockham disliked this video.

I bet the branched off version of Sean that got all zeros TWICE is really confident in Many Worlds right now...

Does this make quantum mechanics the world's most advanced "cargo cult" ?

1:03:30...I’m no expert, but if there is a panel of 4, each arguing in favour of a different interpretation of quantum mechanics, and the Copenhagen interpretation isn’t one of them, then I really do not think that this is a fair representation of how the mainstream physics community consensus is divided. Bohr’s interpretation remains the orthodox one, overwhelmingly.

I have an enormous respect for Sean Carroll as a wonderful physicist and educator, but I fundamentally disagree with him on this topic. I'm surprised that many brilliant theoreticians assert that the wave function IS the physical system. The wave function gives the STATE of the system. The electron is what it is, i.e. one of the fields of quantum field theory, so it is a serious mistake to confuse it with its wave function, which is none other than a computational tool. Basically, the classical analogue of what Sean is saying is that position and velocity of a particle do not describe its state, they ARE the particle. Advocating such a point to me is bullshit. Check out Carlo Rovelli's relational interpretation of Quantum Mechanics for the real physics, as opposed to this metaphysics.

This video sounds heavily edited, especially from 29:00 - 31:25. Was it edited? If so, I prefer the free form format better. Still, was a great podcast.

we need video or this podcast didn't happen.

At 25:47 and around there is talk of "Cloud of probabilities", "wave function", "a machine you ask a question and gives you a probability of a certain outcome". Given all of this, I still have no clue why on earth Sean's notion of realism is still anchored linguistically to an IS, and metaphysically to EXISTS, when it is evident neither category corresponds to the probabilistic base reality indicated by quantum mechanics. To many (like Frederick Stjernfeld and, long ago, to Charles S. Peirce) this has been evident and have proposed a revision (not only of definitions like "measurement" and "observation" but) of the notion of reality and realism itself. In short, base reality is probabilistic and not deterministic, the logic rules limited by non-contradiction and excluded third might not apply, thus, an ontology based on what something IS cannot reflect physical reality, just linguistic conventions about it. For that, it has been proposed that WOULD BE/probabilistic (instead of IS/deterministic) logics can better understand relations and interactions (entanglements) between quantum systems. Nevertheless, Carroll's notion of reality and, thus, his realism tends to be tainted and confused by this (anyways, my two cents, from a semiotics perspective on the matter).

Nice👍🏻👍🏻👍🏻👍🏻👍🏻👍🏻

These would have been very good podcasts without a religious view on MW

Oooo-ooooo- Momma?!

If everything is predetermined and choice is an illusion the many world theory seems obselete

Is this even a theory, is it even testable? Does it make any predictions about anything? And if not what makes it any better then any other non testable beliefs that are not falsifiable? Like god created the universe or any variation of that? Isn't the simplest explanation better? Like quantum systems are tiny unstable systems that are disturbed when measured thus the limitations of interacting with then directly... But they work wonderfully in large quantities with very precise probabilistic outcomes?

I am always impressed with your clarity of thought Sean. This was a very fresh way to frame the curiousities of QM. For anyone interested in a random recommendation, there is a somewhat related Google Tech talk about the quantum "conspiracy" that is quite good: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-dEaecUuEqfc.html

6:55 What kind of licence to talk to people are they talking about?

Rob Reid sounds like Jake Tapper a little.

Welp. This ruled. Again.