I had some spare minutes the other day, and had been thinking about the fate of spacetime in a quantum universe, so I took to the internet to let my feelings be heard. Only a few minutes, though, so I took advantage of Twitter rather than do a proper blog post. But through the magic of Storify, I can turn the former into the latter!
Obviously the infamous 140-character limit of Twitter doesn’t allow the level of precision and subtlety one would always like to achieve when talking about difficult topics. But restrictions lead to creativity, and the results can actually be a bit more accessible than unfettered prose might have been.
Anyway, spacetime isn’t fundamental, it’s just a useful approximation in certain regimes. Someday we hope to know what it’s an approximation to.
Very interesting, but this is why God invented the blog.
The Storify link included in the email notice doesn’t work. Try this one:
https://storify.com/seanmcarroll/spacetime
You need a vacation, my friend. Very badly! 🙂
Personally, I don’t consider spacetime to be overrated anymore than I consider Newton’s theory to be overrated. Not being fundamental doesn’t imply a lower rating. They were huge advances in how existence has been perceived with revolutionary consequences. It’s not clear to me that any theory is more than a model that captures key aspects of phenomena (unless the universe is a morphism of mathematics a la Tegmark or perhaps from Quantum Information as Dr. Carroll points out).
Dear Sean, our research confirms “space-model has no counterpart in the physical universe. Time is merely a mathematical parameter of motion in quantum vacuum.
yours amrit
I would think that time is decomposable and that space is not. Isn’t time, in its most reduced form, the act of space being manipulated and changed? Isn’t energy, in all its forms, the quantization of time’s effects? What is creating the upper and lower boundaries? In both cases, time. Was it James Hill and Barry Cox who published a paper on what happens when we take physics past the speed of light? In 2012 or something? Bring up something this outside the box and people call you crazy, and admittedly Hill and Cox are a little exuberant, but it’s forgivable since they are mere mathematicians. The point being that what Hill and Cox did is exactly what’s required if we are to derive something beyond the antiquated ‘spacetime’. And I agree; there’s something on the tip of the community’s tongue, something that we don’t quite know how to describe. Those at the top of their game, thinking 20-50 years ahead of the rest, know that we’re ready to find out what it is and that we need to find out what it is.
I’ve really been questioning whether or not we could ever truly understand what that more fundamental property beyond spacetime is, since it is beyond space and time. If we are slaved to space and time and can only really go beyond one at a time, but not the other. But I guess that doesn’t make much sense because if that were the case, then why is the limit at space and time? All I can really say with any certainty is that you seriously need to watch Rick and Morty if you haven’t already. Just one episode, ~27 minutes.
@bostontola’s comment raises some questions I was pondering recently. Is one scale more real than another? Is looking at the light year scale more or less real than the meter scale; is either more or less real than the nanometer scale, or the Planck scale? Does the fact that behaviour at different scales requires different mechanics change how real, say, a galaxy, a person or an atom is? Is a more fundamental mathematical description more important even when it’s effects are not visible at different scales? e.g. Relativity is a more fundamental, more accurate description, but when driving a car, the precision with which we can measure acceleration is many orders of magnitude less than the accuracy supplied by Relativity. The behaviour of the septillions of atoms in a car blur out any effects that quantum mechanics might describe.
Considering nonlocal basis of spacetime feels like return to holographic principle to me. Or at least to my naive understanding of it. The space does not exist, it’s just a projection of what is behind it. Like in Plato’s Cave.
Iambic pentameter, bro’, iambic pentameter. I mean, it’s physics, right?
I coincidentally ran into you last year at the Barnes and Noble in Manhattan after the World Science Festival. I would love to hear your thoughts (and how they may differ) on Unger and Smolin’s book, The Singular Universe and the Reality of Time. After reading your two books, as well as all your blog posts for the last three years (and many others) I feel, given your current interests, that this book would have enormous implications in your particular field of inquiry. If you can find the time 😉
I would argue that Minkowski spacetime is fundamental and essential to our future understanding of the universe.
Ran into this idea about time (https://en.wikipedia.org/wiki/Sam_Vaknin) and thought it was interesting altho perhaps wrong, but here it is if anyone wants to consider it.
Work on chronons and time asymmetry[edit]
A model of quantised time was proposed by Vaknin in his 1982 Ph.D. dissertation, titled “Time Asymmetry Revisited”. He postulates the existence of a particle (chronon). In the proposed theory, time is the result of the interaction of chronons, very much as other forces in nature are the result of other particle interactions. Vaknin postulates the existence of various time quarks (up, down, colors, etc.) whose properties cancel each other and thus the arrow of time is derived (time asymmetry). The postulated particle (chronon) is not only an ideal clock, but also mediates time itself (analogous to the relationship between the Higgs boson and mass). In other words, what we call “time” is the interaction between chronons in a field. Chronons exchange between them a particle and thereby exert a force. “Events” are perturbations in the Time Field and they are distinct from chronon interactions. Chronon interactions (particle exchanges) in the Time Field generate “time” and “time asymmetry” as we observe them.[12][better source needed][13][unreliable source?]
Robert– I don’t think Unger and Smolin are on the right track. Everything we know about the fundamental laws of physics points to complete symmetry between past and future at the fundamental level, and an eternalist picture of time. I would need a very strong reason to throw all this out, which I don’t see.
“But! #spacetime is kind of overrated.”
As Woody Allen said, I hate reality, but it’s the only place I can get a decent steak. 🙂
Spacetime or( space or time) may be some emergent reality with respect to some higher dimensional fundamental reality about which we have no scientific knowledge. But whether a reality is fundamental or emergent depends upon the perspective. Spacetime as we know and experience may be an emergent entity with respect to some higher dimensional entity but with regard to matter and energy, space time may be fundamental. Space and time can exist devoid of matter and energy but reverse of this not true.
Curvature of spacetime needs to be a physical reality otherwise what is the meaning of curvature if space and time are not tangible physical realities. This is possible only if space and time are some physical entities
Storified not totally compatible with Firefox/40, but IE11 works!