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An experiment caught a quantum system in the middle of a jump (2019)
- ulam2 6y agoIt wouldn't surprise me if they find that time too is discrete.
- brainfish 6y agoI would be surprised if it is not, given the success of spacetime treating it as just another dimension.
- wetmore 6y agoWhat does that have to do with it being discrete?
- SideburnsOfDoom 6y ago"A Planck time unit is the time required for light to travel a distance of 1 Planck length in a vacuum" https://en.wikipedia.org/wiki/Planck_units#Planck_time_and_length https://en.wikipedia.org/wiki/Planck_units#Planck_time_and_l...
- nine_k 6y agoI don't know about any experimental proofs that either time or space is definitely discrete, or definitely continuous. Both Planck length and Planck time are way too short for current experimental techniques.
- sweetheart 6y agoSlightly unrelated but your comment led me to actually learning what the Planck length is, and the Wikipedia article for it has a great section on how to visualize it [1]. Figured others might enjoy this! 1. https://en.wikipedia.org/wiki/Planck_length#Visualisation https://en.wikipedia.org/wiki/Planck_length#Visualisation
- baja_blast 6y agoI am unconvinced that time is a real dimension, sure we can model movement/interactions of particles as a 4th dimension, but nothing in our understanding of physics requires it being a physical reality. IMO it's less space-time and more just space, it's just the rate of change slows with more mass.
- jhayward 6y agoThere's at least one prominent physicist [1] who is working on showing that time is an emergent property of quantum physics rather than a fundamental one. [1] https://www.preposterousuniverse.com/blog/2013/10/18/is-time-real/ https://www.preposterousuniverse.com/blog/2013/10/18/is-time...
- AnimalMuppet 6y agoIf time isn't real, then when you say "rate of change", I ask "rate of change with respect to what?"
- advanced-DnD 6y agoHe's not claiming time isn't real, which the definition of "real" is difficult and troubling to define in itself. I think he doesn't consider time to be 4th (or part of 3+1 or \R^3 \times \R ) dimension... or in heat equation language: that the domain is a not parabolic cylinder.
- sweetheart 6y agoCheck out "The Order of Time" by Carlo Rovelli! You might find it interesting. He explains (WAY more eloquently than I could) that time is most likely an interpretation of underlying physical law, rather than a fundamental part of it! An illusion, if just a fancy one.
- AnimalMuppet 6y agoI have a hard time buying that, given the Lorentz Transform. Time is just as much a real dimension as space is. (Or are the dimensions of space also "an interpretation of underlying physical law"?) I believe the Lorentz Transformation more than I believe eloquent arguments.
- SideburnsOfDoom 6y agoCorrect https://simple.wikipedia.org/wiki/Planck_time https://simple.wikipedia.org/wiki/Planck_time https://en.wikipedia.org/wiki/Planck_units#Planck_time_and_length https://en.wikipedia.org/wiki/Planck_units#Planck_time_and_l...
- krastanov 6y agoVery much not correct. The Plank time is a rough scale at which we know that our theories do not work. That might mean that a new discrete theory appears there (which is frankly quite probable), but we most certainly do not know whether that is the case and it is just as possible that the underlying theory is continuous.
- zepto 6y agoThat doesn’t say it’s discrete. Only that there is a limit to precise measurement.
- SideburnsOfDoom 6y ago> That doesn’t say it’s discrete. Possibly not discrete, as we envisage it - the small scale does not usually follow human intuition at all. Though I would say that "there is a limit to measurement" of length and time entirely. Not just to accurate measurement.
- advanced-DnD 6y agoI'm working in a field where m=1 and hbar as a semiclassical scale is given as order of N (number of bosons or fermions), i.e. I don't do actual real physics... But.... a thought experiment: If a particle experiences time differently dependent to its speed in relative to a frame of reference, i.e. that time experienced is scaled according to its speed. Since speed is definitely not discrete, scaling it with time, even though time in itself is discrete as you claimed, still makes the time experienced for said particle to be continuous, no? Is this not a contradiction?
- BoiledCabbage 6y ago> Since speed is definitely not discrete, Why is it definite that speed isn't discrete? Distance is discrete in plank length, and time is discrete in plank time. Speed being distance over time, is one discrete unit over another. Isn't it by definition discrete? At a macro level we may abstract over it's discreteness, but isn't it necessarily discrete if it's made up of discrete units?
- RhodoGSA 6y agoIsn't that one of the things that fall out of relativity? that i could never be able to say if i'm the one at rest or if you are at rest?
- phailhaus 6y agoOne experiment suggests that time is an emergent property of quantum entanglement. [1] "A static, entangled state between a clock system and the rest of the universe is perceived as evolving by internal observers that test the correlations between the two subsystems. We implement this mechanism using an entangled state of the polarization of two photons, one of which is used as a clock to gauge the evolution of the second: an "internal" observer that becomes correlated with the clock photon sees the other system evolve, while an "external" observer that only observes global properties of the two photons can prove it is static." [1] https://arxiv.org/abs/1310.4691 https://arxiv.org/abs/1310.4691
- thricegr8 6y agoI'm not sure "quantum leaps" were ever seriously described as "instantaneous". Headlines like OP haven't done much service to the more concrete (albeit layman) definition; when we are talking about quantum speed limits and propagation, what we are really getting at is the speed at which information is propagated through spacetime. When we talk about the cosmic speed limit and why nothing can travel faster than light, that's what we are really trying to describe. Not that nothing can travel faster than light, but rather information propagates at a certain speed, which also just so happens to be the speed of light. The consequence is of course that nothing can travel faster than the speed of information propagation, not even "quantum leaps".
- TchoBeer 6y agoWhat is "information"? Is it a physical thing?
- jakeva 6y agoIt is in the same sense that entropy is a physical thing. https://en.wikipedia.org/wiki/Information_theory https://en.wikipedia.org/wiki/Information_theory
- kgwgk 6y agoWhich is not, really. At least not as clearly as other things.
- avmich 6y agoIt's a bit like saying Maxwell equations are not as clear as Newton's laws.
- kgwgk 6y ago“entropy is an anthropomorphic concept, not only in the well-known statistical sense that it measures the extent of human ignorance as to the microstate. Even at the purely phenomenological level, entropy is an anthropomorphic concept. For it is a property, not of the physical system, but of the particular experiments you or I choose to perform on it.” http://www.lptms.u-psud.fr/membres/trizac/Ens/M2MQPL/Jaynes_entropy.pdf http://www.lptms.u-psud.fr/membres/trizac/Ens/M2MQPL/Jaynes_...
- bosswipe 6y agoDiscussion 2 years ago: https://news.ycombinator.com/item?id=20105091 https://news.ycombinator.com/item?id=20105091
- sandebert 6y agoWhen I'd studied physics, they thought the duration of a collapsar jump was exactly zero. But a couple of centuries later, they did a complicated wave-guide experiment that proved the jump actually lasted some small fraction of a nanosecond. Doesn't seem like much, but they'd had to rebuild physics from the foundation up when the collapsar jump was first discovered; they had to rear the whole damned thing down again when they found out it took time to get from A to B. Physicists were still arguing about it. The Forever War (1974) by Joe Haldeman
- davidhyde 6y ago> "Yes, it is shot through with randomness — but no, it is not punctuated by instantaneous jerks. Schrödinger, aptly enough, was both right and wrong at the same time." What an awesome way to conclude an excellent article!
- fungiblecog 6y agoSorry but the premise of this is bollocks. An atom moving between quantum energy states is in a superposition of the "before" and "after" states for some finite time which is related to the energy of transition. Just because that superposition was never observed does not mean it was thought not to exist.