How long until Greg Egan writes a novel based on this concept? It should be right up his alley.
Interesting that everyone automatically defaults to Greg Egan when thinking of hard mind-bending sci-fi that explores concepts like these. I don't even remember how I got into Greg Egan, but do you have any other favorite authors who play with concepts like these?
In my head, Greg Egan is filed under the "Math-Fi" directory, as that's what I generally associate him with but he's very well versed in pretty much everything (Biology, Physics, etc).
Physics is a description, maths is the best method of describing things in physics, but when things head to infinity it's a sign that the descriptive system is breaking down.
Time can be a dimension and still be treated differently. In fact, in special relativity, it is. When calculating the spacetime "distance" between two events, we use something that looks like the Pythagorean theorem, but we must always make sure to put a different sign in front of time than we do space. (If we sum the squares of space, we must subtract the square of time) (see: minkowski metric, really any metric) An…
A big source of confusion is dimension as mathematical vector element vs spatial dimension. These are different concepts. Still it is interesting that x, y, and z seem identical while t is intrinsically unidirectional. Why?
Not a physicist -> My assumption is that this is because x,y,z are just constructs to model physical space. They don't exist and we could just as well describe space with cartisian coordinates or some other system where the dimensions would not be isometric. Meanwhile, as you point out, t as a vector is also itself a convenient model for something, not an actual dimension.
The idea of "spacetime" makes a fun narrative, fun thought experiments, and interesting ways to graph and visualize events. But many physicists wish that popularizing this concept would stop and go away, because it is misleading. There is both evidence and theoretical work demonstrating that time, unlike the spatial dimensions, is not a choice when it comes to direction of travel, and never will be. The definition of…
I really like the presentation in one of Lev Landau's books. He calls it a fictitious 4-dimensional space. That's the correct way to look at it, spacetime is just a mental model, a tool for describing physical laws. So depending on the mental model or framework we decide to use, time can be a dimension or something completely different.
The idea of "spacetime" makes a fun narrative, fun thought experiments, and interesting ways to graph and visualize events. But many physicists wish that popularizing this concept would stop and go away, because it is misleading. There is both evidence and theoretical work demonstrating that time, unlike the spatial dimensions, is not a choice when it comes to direction of travel, and never will be. The definition of…
My take on it is that special relativity provides no evidence that time is an extra dimension (like the spatial dimensions) in anything but a mathematical sense. General relativity however has quite a lot of effects that mingle together space and time in various ways, so I'm still thinking about that one.
> no evidence that time is an extra dimension (like the spatial dimensions) in anything but a mathematical sense
What do you mean by time being an extra dimension in non-mathematical sense? Dimensions and space are mathematical concepts.
Simply beautiful thoughts. I love the idea that the atoms of our bodies are replaced over the years - that no part of me today was a part of me in my twenties - and this concept, the braid in spacetime, puts it more eloquently and more bravely than I could think. It's great to be able to take words written by some guy on another part of the world and have them rearrange my brain and my thoughts - this is beautiful.
I like the naiveté of this comment, it reminds me what HN used to be, a place for wonder and discovery. Thanks for your comment.
Makes me wonder what I was smoking ... I must get some more ;)
Speaking as a physicist, I in general like this article, however there is a nasty technical point to make, which is that if you actually use distance units to measure time, we look like the "inanimate object, simple pattern", not the "living object, complex pattern." Moreover the "death, disintegration" slide is not going to be what you look like unless you happened to be in the vicinity of a bomb at your death. Stil…
As a trained, but non-practicing, physicist, I would like you to elaborate about your first paragraph. I am used to using units where c=1, I think that is what you are referencing: a "meter" of time is the time it takes light to go a meter (which is to say, a very small amount of time) and so a second is 3x10^8 m. I don't see how this changes the pattern we would make in spacetime. If we assume no one ever moves (a nice physics-y approximation), but the particles that make them up do, so I don't see why we wouldn't look like the middle pattern while alive. Then after death, the disintegration is exaggerated, but again, it seems more-or-less right to me. What am I missing?
I'll buy that your spacetime braids disintegrate at death altho i'd think they be more like the parallel braids of a stone, not like those shown helicoptering out as in the picture.
But as for birth, clearly your start branches off of the braids of your mother. and so start immensely tangled to begin with.
I'm studying topological quantum computation, and in this field one considers particles confined to 2 dimensions called anyons. As a collection of anyons move around, the paths they take in spacetime "tangle together" and have the structure of an element of the braid group (https://en.wikipedia.org/wiki/Braid_group). Two anyons cannot exist at the same place and time, and thus their world lines cannot pass through each other. This is useful, since any sort of physical error in the system will preserve its braid structure, saving the need for quantum error correction.
This article is mostly fluff (except for the two diagrams, whose captions contain more content than the article), but I'm sure it makes an interesting read for those wishing for light philosophical thought rather than deep and novel technical concepts.
The idea of "spacetime" makes a fun narrative, fun thought experiments, and interesting ways to graph and visualize events. But many physicists wish that popularizing this concept would stop and go away, because it is misleading. There is both evidence and theoretical work demonstrating that time, unlike the spatial dimensions, is not a choice when it comes to direction of travel, and never will be. The definition of…
dahart: >> has been mistranslated in popular science culture as a thing that somehow opens up the option of time travel.
Ah, time travel isn't science fiction. Clearly we have concrete experiments that show this is common place, easy and done all the time.
The faster you go in the space dimension, the slow you move in the time dimension. Now certainly being able to go back in time is something of speculation, and more the realm of science fiction. but that you can jump into other people's future is fact.