Least Action Q&A Session With Casper and Derek
Added 2025-04-07 20:03:27 +0000 UTCThe much anticipated Least Action 2 Q&A!
We had so many insightful and intriguing questions it was hard to choose what to include.
There are two subsections in this video, the first part focuses on least action in general and the second on the demonstration that Casper showed us.
Thank you so much for all your questions and engagement, it was a pleasure to read through them and we hope you enjoy this video.
Comments
If you repeat the laser experiment 2 thoughts, use a first surface mirror and make sure you use the correct diffraction grating but on second though better still make sure to read Gratings as dispersive elements from wikipedia to make sure this is not what the experiment shows.
Kat Seibert
2025-09-10 20:41:20 +0000 UTCThe issue with this is it then differentiates living things with inanimate objects. Since we are all made of matter we should follow the same laws as a ball for example and this theory would state that living things have an entirely artificial property that supersedes matter in general. This also assumes that right now there are other dimensions that can be tapped into. Our understanding of dimensions is very small but scientists currently believe that the universe is in 3 dimensions due to it being the most stable on the quantum level and at the big bang there were many dimensions that didn't "make it". Whatever you believe about dimensions, the fact that our universe is in 3 highlights the fact it's probably the only way anything can exist (bit like how a pyramid is the most optimal shape in nature and a bee uses hexagonal shapes for a hive as it is most optimal). Optimisation is a driving force that may have been the reason our universe works so well and hasn't just collapsed in on itself. Basically in full, your theory can be comforting to those who do believe humans have this separate special quality that means that the "experience" of life being cut short is not simply just the human body breaking down but a "soul" dying that can maybe just be a possible path. I personally don't believe this, I believe we are a very articulate and beautiful result of math that allows a system, our universe, to simulate what's happening because if we weren't able to do that the universe would just be and no one would ever know.
Jude Nash
2025-06-04 17:19:18 +0000 UTCI’d like to share a theory that’s been on my mind for a while. At first, I dismissed it as just a foolish thought—but then I came across this video about the principle of least action, and suddenly, something clicked. The principle of least action is known to apply to light, but what if it applies to all matter? Maybe it’s not such a wild idea after all. What if every particle of matter is not only following the path of least action, but also simultaneously exploring all other possible paths—just not in ways we can directly observe? Here’s where it gets interesting: perhaps those alternate paths are being taken in dimensions we can't perceive. As individuals, we only experience one version of reality, the one where our particles follow a specific path. So—bear with me—what if the reality we're experiencing right now is the "dimension of least action"? If that’s the case, then every possible version of ourselves could be exploring different paths through different dimensions simultaneously. Among them, there might be one path that is more "efficient" or "optimal"—the one where the path of least action dominates. That would be the version of ourselves we’re most likely to experience: the one that lives the longest, progresses the furthest, and makes the decisions that move us forward most effectively. Let’s call this reality the Dimension of Least Action. But what about others—people who seem to have been tragically cut short in this dimension? It might be that they're not experiencing their dimension of least action here. In your dimension, they could be taking a less optimal path, while in their own dimension of least action, you might be the one on a suboptimal course. Everyone could be navigating their own version of the universe, with different people playing different roles depending on whose optimal path is being followed. So, the big question is: how could this ever be proven?
Michiel Nugteren
2025-05-30 19:32:59 +0000 UTCwhy choose patreon not YouTube?
Jazsajral
2025-04-23 21:19:50 +0000 UTCIt's nice to see that you mentioned my dust particle doubt. What brings me there is that lasers focus light to a tight spot, and only due to atmospheric reflections do we see its path. So, for me, conceiving that experiment is possible only when it's done in a vacuum.
SYED BADIUDDIN ANAS
2025-04-20 02:47:30 +0000 UTCAn issue I take with the demo from the main video is saying that "it's just interference/diffraction". interference is a property that derives from the hamiltonian principle and does in fact show exactly what you say it should. For the same reason the laser case shouldn't work. For a reasonably collimated gaussian beam, the action outside the beam should grow very very fast (much closer to a massive object than a spherical wave from the lamp case). So the phase winding that is supposedly broken by the diffraction grating is much faster than the line frequency of the grating and would still cause destructive interference. (this would otherwise also probably break most laser experiments, which very often use similar gratings. And having worked in a laser lab, gratings do not usually reflect light if you miss the grating (which is equivalent to blocking the mirror in the demo))
WolframConda
2025-04-09 23:50:43 +0000 UTCMartin H., like Feynman’s double-slit conundrum, your excellent question zeros in on one of the deepest mysteries of quantum mechanics: How can an almost infinitesimal small packet of conserved electromagnetic energy manage to “be aware” of _every_ possible path that it travels, particularly in cases such as large Einstein lenses where “every path” may encompass a sizable fraction of the entire universe’s volume? For anyone who has worked or thought about any form of electromagnetic information transfer, the classical version of “being aware” of those paths has energy and bandwidth implications: You cannot hear a radio station that lacks enough energy, and you cannot encode vast amounts of energy onto an AM signal. You need _both_ more energy (to get the result in a finite time) and more frequency (to add more information) to capture that awareness of where the photon traveled. Being aware of the structure and shape of the _entire_ Einstein lens — all of its matter and dark matter and the exact distributions of that matter, since otherwise the photon cannot know exactly where it needs to go — is even more daunting. And that destination could be a single focal point with an almost 100% arrival probability! And yet, to a photon, the task of focusing across most of the universe seems no more and no less complicated than the same photon traveling through a camera lens with its version of vast complexity in the form of atoms. Thus, your excellent question: How does “awareness” work in the quantum world? How can it handle such incredible scaling feats using almost infinitesimal energies? What is the deeper nature of this remarkably energy-efficient quantum version of the classical concept of information? The maths do not help, since they only transform the same observation and question into a far more cryptic form: A “wave function” that _itself_ requires infinite energy and infinite disregard for the lightspeed restrictions of classical information. Where is the path to resolution? Did you know wave functions _do_ have physical properties, and can you trivially detect and partially reduce such wavefronts without involving individual atoms? When an experimentally meaningful quantum wave function — a photon or Schrödinger wave — arrives at a reflective surface, it deposits a tiny but measurable bit of momentum there. This deposition is no small issue in astrophysics since, for example, it is how the Pillars of Creation formed, and how similar processes once formed our sun. NASA uses the momentum of individual photons on solar sails to accelerate probes through space. Yet when the photons deposit this momentum, they _only_ deposit as waves that lap evenly against the _entire_ surface of a dust particle or NASA solar sail. The photon never “sees” the detail of that particle or sail, only its broad shape. From that one hint, Martin H., I can add to this discussion a hint towards the deeper answer you seek, but nothing more than a hint: A photon traveling through an Einstein lens does not “see” those galaxies in any more detail than it “sees” the atoms in a focusing lens. The deeper physics hiding beneath classical waves and classical particles is scale-free, meaning the photon is only “aware” of an incredibly tiny fraction of the complexity of those galaxies — and even there, only in the sense of gathering an extremely small bit of their complexity in the form of momentum as its wave front form passes through them. The nature of the transfer is neither mysterious nor unknowable, but a real change we see in the shaping and shifting of the photon front. Linear momentum — acceleration, really — scales in remarkable ways that energy cannot, and through that scaling shapes and transforms the wavefront path of the traveling photon. This extreme non-linearity of linear momentum is at the heart of your mystery, although by itself, it is far from a complete solution to the mystery of choice and rescaling.
Terry Bollinger
2025-04-09 19:00:04 +0000 UTC5:35 Martin H. (MH): How does something have the energy to try every possible path all at once? Wouldn't that require infinite energy? [5:34] 5:43 Derek Muller (DM): Hmm. It's a great question. I think the particle only ends up sort of, eventually, taking some paths. Right? I think we were careful in the script to say, "explores all possible paths" as opposed to "takes all possible paths." If we're talking about a photon or a particle, it starts in one place and ends in one place. So, in that way, you don't have more than one electron or something. But, while the electron is traveling and not interacting with anything, it must be aware of what paths are open to it. So, that's a very weird thing to think about. But I don't think it would break any conservation laws, or say that, "Yeah, we need more electrons or more energy." It just says that the electron we have needs to be aware of all possible paths. So it needs to be kind of exploring all directions. And then, ultimately, action kind of determines where the thing is going to end up. [6:42] 6:43 Casper Mebius (CM): I think that's spot on. I was talking to Dave about this, and he said, "You know, as long as you're still in sort of the quantum space where you're talking about just the wave function, it can do whatever it likes." You know, you can have these virtual particles, for example, that pop into existence, that go out of existence. But as long as in the ultimate reality there's a net zero energy gain or loss, then all of that is fine. But you have to include all of those still in your calculations. [7:09]
Terry Bollinger
2025-04-09 18:54:23 +0000 UTC
