Sean Carroll
Blog post with audio player, show notes, and transcript: https://www.preposterousuniverse.com/podcast/2019/09/09/63-solo-finding-gravity-within-quantum-mechanics/
Patreon: https://www.patreon.com/seanmcarroll
I suspect most loyal Mindscape listeners have been exposed to the fact that I’ve written a new book, Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime. As I release this episode on Monday 9 September 2019, the book will officially be released tomorrow, in print, e-book, and audio versions. To get in the mood, we’ve had several podcast episodes on quantum mechanics, but the “emergence of spacetime” aspect has been neglected. So today we have a solo podcast in which I explain a bit about the challenges of quantum gravity, how Many-Worlds provides the best framework for thinking about quantum gravity, and how entanglement could be the key to showing how a curved spacetime could emerge from a quantum wave function. All of this stuff is extremely speculative, but I’m excited about the central theme that we shouldn’t be trying to “quantize gravity,” but instead looking for gravity within quantum mechanics. The ideas here go pretty far, but hopefully they should be accessible to everyone.
The end of this episode includes a bonus, a short snippet from the audio book, read by yours truly. Audio excerpted courtesy Penguin Random House Audio.
Source
In another branched off universe, I might feel like the Many Worlds theory has got something to do with reality.
nothing lives without cooperation. structure and common purpose are the most fundamental ingredients to life, Yet we are more divided than ever. Unity is just like water. cooperate or die.
I wasn’t aware that Sean had a podcast. I love it
But there is high dimensional continuum of positions of the cat, not just asleep and awake. So are there an infinite number of observers outside the box even before it's opened? How far away can the observed by to avoid this locality effect?
tl;dr did he find it? where was it hiding?
In my 7 years of doing physics I’ve never heard anyone describe fields in this way. Thanks for teaching me that! I really enjoy your podcast and all of your books!
You are an EXCELLENT professor Sean. Thank you Very Much for your devotion.
So you've got Hilbert space wrong. You must be talking about a very specific Hilbert space. In general they can have as few as 1 dimension. A Hilbert space is just a complete, normed vector space together with an inner product function.
For example the vector space R2 (2 dimensional reals) with the standard norm ||(x,y)||=sqrt(x^2 +y^2) and the standard dot product (x,y)•(t,u)=xt + yu is a fairly simple 2-dimensional Hilbert space
Quantum mechanics: "The most spectacularly successful theory that physicists have ever devised…And yet we still don't understand what it actually says."
Yep…Sounds exactly like my life!!💡🤦🏻😫 😂
For a new theory of two dimensional time in quantum gravity and more look at : https://philpapers.org/archive/OZTNII.pdf
In my universe, there's only the sleeping cat (and hungry cat)
jokes aside, I don't understand much, but this does sound interesting 🙂
Is there any validity in thinking of the future as the wave function of the universe in superposition?
Thank you Sean!!! One comment though, you end a lot of statements with “OK??”. But often those statements are of such magnitude as “space is the property with respect to which interactions are local. OK?” If you are asking, which the intonation would suggest you are, the answer is No! They don’t just absorb like that. Again thanks for this one, I’m going to have to listen to it many more times, but for future reference when you ask “OK??”, just know the answer is “NO!!! Not yet” lol
another big fan here filled with awe for your easy style, mr carroll.
i do enjoy that you do not say a word ABOUT consciousness anymore. but you put my mind in a very agreable state with everything else. thank you.
does the entropy rise because the universe branches?
Hi Sean, I doubt you'll see this and respond, but I have listened to all of your lectures and podcasts on QM and there is something I still don't understand about many-worlds. It essentially boils down to: why do we ever observe something "particle like"? It would seem as though if everything (including ourselves) is wave-like then we would simply observe things to be wavelike, even if we are beginning to be smeared across possibility space and are only observing parts of the wave. Where do these point-like events suddenly come from? I have a feeling it has to do with that part about chopping up the wavefunction into localized pieces of space in a unique way, but that's going way over my head.
All of what you said. No
In digital electronics, the AND gate has the following logic behavior, where A and B are two separate inputs, and C is the combined output:
A B C
0 0 0'
0 1 0
1 0 0
1 1 1
the wave function "breaking down" is simply to say that upon direct observation of the object of measurement, the uncertainty is gone. the wave function is simply a mathematical approximation of uncertainty. I can't see that observation has any bearing on entanglement.
we never actually see (observe) superpositions…..because they are a purely theoretical construct, they do not exist in reality. think of superposition as a paradox, which was the point of Schrodinger's experiment.
Schrodinger's cat is a fraud. "cats" do not show quantum behavior. Cats and humans exist on the macro scale, not the quantum scale.
one of the problems with measurement, is that the measurement can or does restrict the process and the quantum behavioral result of what is being measured. for example, in the double slit experiment, firing photons through the slits produces dots. transmitting a beam of light produces a wave interference pattern. In other words……
dots produce dots (the input was restricted)
waves produce waves or interfering wave patterns. (the input was not restricted)
so what knowledge was gained here, isn't this exactly what we would expect to happen? this experiment really told us nothing meaningful about QM.
yes, gravity cannot be quantized, because it is a consequence of the deformation of spacetime, it is not a fundamental force. Gravity is only an emergent property of the formation of massive bodies, and of the vacuum energy of space.
Really enjoying these solo episodes, Carroll is a legend.
Hi Sean, can you say that when we observe a part of our universe we are forcing that part of the universe wave function to collapse and hence we are somehow changing the progress of its flow?
Is it necessary to have the different outcomes be branches. I can easily envision the parallel outcomes having parallel backstory as well. Entirely identical until the day of the fateful cat-napping.
Great podcast! Just one error: quantum mechanics is NOT "more fundamental" than General Relativity. General Relativity has never failed a single experiment and the discovery of gravitational waves put that to rest. Spacetime is more fundamental than the particles that inhabit it.
The universe splits into what? Hyper space? Where or what are these universes splitting into?
So, if photons can entangle with other particles (also other photons?), causing decoherence, then what about neutrinos? Aren't neutrinos even better "monitoring particle" ? Or rather monitoring wave excitement.
The observation of a positive cosmological constant has been recently called into question, see: A crisis in cosmology – the shape, age and content of the Universe – https://arxiv.org/abs/1911.02087 … Anti-de Sitter space is looking more plausible after all then? Seriously, people should be going down both paths (positive AND negative) in this field… it's not as though there aren't enough researchers to tackle both sides, right?