Sometimes the universe is unpredictable. (Nobody needs to be reminded of that just now.) Is that unpredictability fundamental, or merely apparent? And how should we deal with it when it comes along?
The Biggest Ideas in the Universe | 19. Probability and Randomness
And here is the Q&A video.
The Biggest Ideas in the Universe | Q&A 19 - Probability and Randomness
I’m certainly no expert; just a “hitch-hiker” on the journey of scientific discovery; but I would make a case for unpredictability being fundamental to our “observable” Universe. I would, roughly, equate this to David Bohm’s “Explicate Order”.
However, if the concept of the “Implicate Order” is taken to its logical conclusion, neither predictability, nor unpredictability can be attributed to the underlying “reality”.
*However*, if I have a bad hand, I may raise in order to make you *think* I have strong hand so you’ll fold. Wheels within wheels…
Thank you Sean for this great series. I have watched each and every one. I hope there will be more to come. I learn something new every time I click the name Sean Carroll. I am very old but still enjoy learning from your videos. Keep them coming please.
How do objective and subjective probabilities relate to Einstein A and B ceficients
A coefficient appears to be Objective (quantum)
B coefficient appears to be Subjective (claical)
Thanks as always for a thoughtful talk. I missed seeing the cat.
1. There seems to be a fundamental disconnect between the deterministic Schrodinger equation and the transformation into probabilities by the Born Rule. I think you wrote a paper trying to derive the Born Rule, no?
2. I’ve always had trouble hearing well meaning physicists try to rigorously explain QM in terms of waves (relying on the Fourier transform etc.). But when we get to the “real world” e.g. the particle that enters the double silt experiment…. the particle becomes “a wave of probability.” Is this just loose language? What would a “wave of probability” be in the “real world”? Is it like a “crime wave”? 🙂
3. I believe you said, “there aren’t any objective probabilities in the real world”. But your explanation of Bayesian probability started with a coin flip as the input. I like the conceptual model of Bayesian probability as the way humans should think about things. But, isn’t most probability (gambling, identifying particles at the LHC, LIGO etc. etc. etc.) based on the frequentist model?
4. I recall the Many Worlds model being criticized on the basis of “what would probability mean in such a model?” Is that because is is Bayesian?
Thanks many times for your kindness.
Sean- Thanks so much for doing the Biggest Ideas. I live in southwest Kansas and the nearest university is about 140 miles away. I am a grandma and retired social worker (over 30 years in the mental health field). I always have been interested quantum mechanics, but never dreamed I would ever have the opportunity to learn as I have.
I have watched all your lectures on Great Courses and many of your speaking engagements on the internet. I have listened to podcasts and looked up lecture notes from one of your classes.
Looking forward towards your new textbook. What is the timeline of it being available to the public?
Someday I hope to be able to thank you in person, but until that day comes- I am very grateful to you for your generosity of time, energy, and other resources that you so freely give. Thank you for your gracious and effective way of sharing your knowledge with the world!
It is great, isn’t it Rhonda. 🙂
No only do we never have complete knowledge of some classical system, there is also the fact that real systems are never completely closed. There are cosmic muons and gravitational waves and neutrinos etc. streaming thru your system that are coming along the past light cone and cannot be anticipated.
Thank you so much for this inspiring series of talks. It made me look around for some other interesting talks and lectures of your colleagues. Maybe this question does not quite fit in here. What about AdS/CFT, the holographic principle, entangled black holes and teleportation through wormholes? I do not have a deep understanding of all the maths behind these ideas. Are there ways to verify these ideas by experiments? Which kind of “machines” would we have to build?
Some physicists say that because fundamental physics is deterministic then everything in the macroscopic world is too, so free will must be an illusion. Does this conclusion necessarily follow from the premise? Could “emergence” change the game on the way up to the exquisitely complex level that is life? And what does “emergence” mean to a physicist anyway?
(Wonderful series!)
William H Harnew
Not really:
–Huw Price..
Everett took the probability out of* probabilistic mechanics and modern Everettians haven’t managed to put it back yet.
* More accurately: he just didn’t recognise that it was there (few if any did at the time).
Hi Sean, let me first express my extreme gratitude for the enormous effort and enthusiasm with which you share your vast knowledge. It is very inspirational and I believe teachers of science and rationality like you are more important than ever and you represent a shining light of optimism amidst a fairly dark time.
I’ve heard you mention David Deutsch on several occasions throughout your excellent “Biggest Ideas in the Universe” series. I happen to be a big fan of his and think he brings a quite unique and original way of thinking about the world and is a fellow Everettian. I would like to request you to please try to have him as a guest on your Mindscape podcast. I believe it could provoke a very interesting discussion between you two and may also expose his ideas to a wider audience.
Again, thank you so much for all you do and I look forward to more of your content!
Paul Hayes
Thanks, Paul, I take your point. I’ll follow up on your references. Always good to check in with Huw Price. I hope Professor Carroll weighs in on this. I’m guessing that Everetians rely on “indexicality” and “self locating uncertainty”… Ha, ha I just ran across his paper on this topic.
https://arxiv.org/abs/1405.7577
I’m also interested in his take on “chaos theory”.
You didn’t even get around to talking about how Gauss figured out that you could extract more accurate results from error-prone data, even when different data sets have different sources of error — and used that to figure out much more accurate orbits for solar system objects.
Or how Laplace applied statistical dynamics to prove that the planetary orbits were “approximately” stable, even though the many body problem is too difficult to solve deterministically using Newtonian gravitation, and is by no means guaranteed to have a stable solution (even 3-body problem can be ugly).
Each of those might contend on their own for one of the “Greatest Idea” slots. Maybe you can cover then in Q&A.
Is the second law of thermodynamics a physical law that is among the fundamental laws of our universe, or is it more of a mathematical/statistical law akin to the central limit theorem that our universe couldn’t not follow given its other laws? Assuming the latter, what features of our physical laws are necessary to make the law of increasing entropy applicable to our universe?
Hi doctor Sean! Thanks for the awesome video! Here’s some questions/requests:
1. Can you please say a little more about the linearity of the schrodinger’s equation? I’ve heard that the linearity of it that assures that the correct evolution in time of this equation would be that every measure gives rise to a superposition, but I cant really see why.
2. You mentioned about the complementarity… I know it’s not the focus of the video, but why position and momentum are a complementar pair, and not position and energy, for instance? Also, can we know about the position and energy of a particle with certainty?
3. Could you please elaborate more about the bayesianism? Specifically, about betabilitarianism and Qbism?
4. (This one I know is kind off topic, but one can have hope, hahahaha) Can you please explain the data collected by the Wigner friend experiment and why it implies that two observers saw different realities? I can understand the data from delayed choice quantum eraser, delayed choice entanglement swapping, bell tests… but the violation of probability in the actual wigner friends experiments is a mistery to me!
Thanks Dr. Sean!
Regarding Norton’s dome, other equations with multiple solutions are regularized by noise, making only some solutions possible in the limit of zero noise. Is this the case for Norton’s dome? Does that make such systems with multiple solutions less rich than chaotic systems?
Hi doctor Sean! It’s me again!
Please, since the topic is probability, can you please explain the CHSH inequality? I guess I understand bells inequality quite well, but i guess it would be interesting to explain it also…
Thanks again!
Could there be a universe where the second law of thermodynamics is reversed?
My question is, if nature always gives an exact answer (even in QM, with measure we get an exact answer), and nature always avoids/solves logical paradoxes/contradictions, can we say that the laws of physics/nature are not exact deterministic as well?
For this reason, I see the probability and randomness always originate from our ignorance, hidden variables, and the inability to know the conditions.
What do you think???
Could you derive quantum mechanics by extending probability to complex numbers? (or sets of complex numbers?)
A dome shaped like h=r^(3/2) has a slope that goes as r^(1/2), and a curvature that goes as r^(-1/2), which is undefined at 0.
If a dome was shaped like h=|r|, with an undefined slope at 0, would we be surprised if a particle’s behavior was undefined at 0?
Is r^(3/2) really any different?
I wouldn’t have thought I was a frequentist, identifying more with Bayesianism, but under many worlds quantum mechanics,
couldn’t you say there would be an “infinite” number of 2020 NBA championships?
Is a heat bath equivalent to embedding in a bigger box of particles?
If you were worried about the smaller box being prepared in special state, what if the bigger box was prepared in a special state?
(and could you argue that the big box was prepared in a special state of very low entropy 13.8 billion years ago?)