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Life is a braid in spacetime

nautil.us

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Re: Life is a braid in spacetime

#11

Post by dahart »

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 time as a numerical order of change in space is replacing the 106-year-old concept of time as a physical dimension in which change runs,” Sorli said. “We consider time being only a mathematical quantity of change that we measure with clocks. This is in accord with a Gödel view of time. By 1949, Gödel had produced a remarkable proof: 'In any universe described by the theory of relativity, time cannot exist.' Our research confirms Gödel's vision: time is not a physical dimension of space through which one could travel into the past or future.”

http://phys.org/news/2012-04-physicists-abolish-fourth-dimen...

Edit: previous thread on HN re this article: https://news.ycombinator.com/item?id=3842734

Sounds like some think this phys.org article is BS. I don't know, I am not a physicist. But I have been wondering for many years whether it makes sense to treat time as a dimension. I assumed it made sense in relativity study, and has been mistranslated in popular science culture as a thing that somehow opens up the option of time travel.

Re: Life is a braid in spacetime

#12

Post by visarga »

madaxe_again wrote: post #7

He does make the rather blithe assumption that mathematics is somehow real, and not an idiopathic artefact of our cognition, as much as the apparently respectively static and dynamic nature of space and time that he notes most posess. Perhaps mathematics is also a stubbornly persistent illusion. Me, I see the universe as information, and everything else flows from that. We are needles scratching out the tune from a h…

> Me, I see the universe as information, and everything else flows from that.

I admire the Integrated Information Theory of consciousness (by Giulio Tononi) a lot. It provides an impressive intuition pump towards the nature of consciousness and the necessary conditions for it to arise. It also goes much deeper than "consciousness is a complex pattern in space-time", by detailing "what does it mean to be complex?", what kind of complexity leads to consciousness and how can we compare various systems to see their degree of consciousness/complexity.

The IIT surely does not give a definitive answer on consciousness, it is not even able to compute an approximate complexity score for the human brain, and doesn't explain why complexity is linked to consciousness in the first place, but it helps us see in many directions where we could only stumble in darkness before.

Re: Life is a braid in spacetime

#14

Post by Ono-Sendai »

dahart wrote: post #11

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.

Re: Life is a braid in spacetime

#15

Post by whatshisface »

dahart wrote: post #11

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…

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)

Another point of interest would be the matrix representation of the Lorentz transformation (the way to go from one reference frame to another). The matrix "mixes" the values of the time coordinate with the space coordinates, and the space coordinates with each other, but time is mixed differently. (This is a nice one to bring up because its clear if you just look at the matrix.)

This is very significant for people wondering about time's status as a dimension. It is emphatically not the same kind of dimension as space, even if we choose to represent it as a component of the position vector.

Re: Life is a braid in spacetime

#16

Post by api »

whatshisface wrote: post #15
dahart wrote: post #11

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…

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?

Re: Life is a braid in spacetime

#17

Post by jdjdirn »

madaxe_again wrote: post #7

He does make the rather blithe assumption that mathematics is somehow real, and not an idiopathic artefact of our cognition, as much as the apparently respectively static and dynamic nature of space and time that he notes most posess. Perhaps mathematics is also a stubbornly persistent illusion. Me, I see the universe as information, and everything else flows from that. We are needles scratching out the tune from a h…

All that can be, is. A mathematical proof is a statement about what can be in a particular system. A system can be anything that can be dreamed, by yourself, or indeed by the universe. Therefore mathematics in it's widest definition is the study of what can be in the universe.

Its like this: If something is to exist, would it not be absolutely absurd that only this exists? This universe in this particular configuration, out of all the possible configurations? It cannot be. Either there is nothing or there is everything. If there is everything then all possible configurations of thing are. Some of those things have patterns within them that 'percieve' the world to be time like. When really the whole thing is timeless, it is like all configurations of thing saved onto one giant hardrive, your life in bits on a 2 dimensional substrate. From the outside its timeless. From the context of you at x,y,z it is timefull.

Is this not totally obvious? How can this not be obviously true to everyone?

Re: Life is a braid in spacetime

#18

Post by astrobe_ »

madaxe_again wrote: post #7

He does make the rather blithe assumption that mathematics is somehow real, and not an idiopathic artefact of our cognition, as much as the apparently respectively static and dynamic nature of space and time that he notes most posess. Perhaps mathematics is also a stubbornly persistent illusion. Me, I see the universe as information, and everything else flows from that. We are needles scratching out the tune from a h…

You can argue that Time is an illusion. You can argue that our intelligence allowed us to break free from the harsh laws of nature and evolution too soon, so we never acquired the necessary sensors and abilities. Maybe if we had to compete against multiple equally intelligent species, we would have acquired them. However, I think that using a "vision of Time as it really is" sensor correctly would require a far more complex and energy-hungry brain, so it's probably not "worth it" from an evolutionary perspective. Or maybe it's out of reach of carbon-based organisms.

However Mathematics are different. It's not a perception. It even allowed us to discover things we could not perceive, and explore things we cannot perceive. It is independent from us and the universe. And if you still want to throw away Mathematics, you'll also have to throw away logic, which is kind of an issue. The only thing one could seriously argue, is that something better than Mathematics exists, like General Relatively is "better" than Newtonian mechanics. But maybe that is out of our reach, too.

Meanwhile, repeat after me: I believe in modus ponens, set theory and monads.

Re: Life is a braid in spacetime

#20

Post by drostie »

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.

Still the question of how we reconcile our sense of ourselves as speech-act-performing free-will-having conscious-feeling observers embedded in a changing world, with a relativistic perspective which says "there probably isn't one constantly-updating 'present' because a 'present' can be any hyperplane between two light cones, and therefore we can never have any physical basis to choose one as the correct one," is one of many really important philosophical questions that I think are important, though not really my domain.

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