<\/p>\n
<\/p>\n
[responsivevoice_button rate=”1\u2033 pitch=”1.2\u2033 volume=”0.8\u2033 voice=”US English Female” buttontext=”Story in Audio”]<\/p>\n
<\/p>\n
Thanks to Kevin Bacon, everybody nowadays knows about networks.<\/p>\n
There are not only Bacon-like networks of actors, linked by appearing in the same film, but also social networks, neural networks and networks of viral transmission. There are power grid networks, ecological networks and the grandest network of all, the internet. Sometimes it seems like the entire universe must be just one big network.<\/p>\n
And maybe it is.<\/p>\n
Physicist\u2013computer scientist\u2013entrepreneur Stephen Wolfram believes the universe is a vast, growing network of relationships that constitutes space itself, and everything within it. In this picture, Wolfram sees the basis for the ultimate theory underlying all of physical law.<\/p>\n
Wolfram expressed something like this view 18 years ago in a 1,197-page tome entitled A New Kind of Science. But back then his picture was still a little fuzzy. Now he thinks he has found a more sharply focused vision for how to explain reality.<\/p>\n
\u201cI\u2019m thrilled to say,\u201d he writes in a summary document released April 14, \u201cthat I think we\u2019ve found a path to the fundamental theory of physics.\u201d<\/p>\n
At the core of Wolfram\u2019s approach is the notion of a hypergraph. \u201cGraph\u201d in this context is like the diagrammatic representation of a network: lines connecting points. But reality can\u2019t be captured by lines linking points on a flat sheet of paper. Wolfram generates computer visualizations to depict relationships in more complicated \u201chypergraphs.\u201d (In a hypergraph, the \u201clines\u201d can connect any number of points, not just one to another.)<\/p>\n
Wolfram\u2019s investigations indicate that complex hypergraphs can mimic many features of the universe, including matter and energy, along with reproducing the physical structures and processes described by the theory of relativity and quantum mechanics.<\/p>\n
\u201cIn our model, everything in the universe \u2014 space, matter, whatever \u2014 is supposed to be represented by features of our evolving hypergraph,\u201d Wolfram writes.<\/p>\n
His key point is that such extremely complex hypergraphs can be produced by applying simple rules to a simple starting point. Suppose you have two \u201cabstract elements\u201d labeled A and B. You have a rule that says every A should be changed to BBB, and every BB should be replaced with A.<\/p>\n
Start with A. By the rule, you \u201cupdate\u201d A to BBB. BBB possesses two BBs. So you update BBB twice: Once, making the first two Bs into an A (making AB), and then making the second two Bs to an A, making BA. So:<\/p>\n
A<\/p>\n
is connected to<\/p>\n
BBB<\/p>\n
which is connected to both<\/p>\n
AB and BA.<\/p>\n
Updates of AB and BA both yield BBBB. But BBBB then makes ABB, BBA and BAB. As you keep on applying the rule, the graph gets more complicated.<\/p>\n
These update steps, Wolfram says, correspond to our common notion of time, a sort of ticktock of the cosmic clock. As a rule is repeatedly applied to a set of abstract entities, the resulting connections \u2014 the graph of the relationships linking them \u2014 correspond to the structure of space. So space (in this picture) is not a mere uniform set of indistinguishable points; rather it is a network of points linked in unfathomably complex patterns that reproduce matter and energy and the relationships collectively known as the laws of physics.<\/p>\n
\u201cThis is basically how I think space in the universe works,\u201d Wolfram writes. \u201cUnderneath, it\u2019s a bunch of discrete, abstract relations between abstract points. But at the scale we\u2019re experiencing it, the pattern of relations it has makes it seem like continuous space of the kind we\u2019re used to.\u201d<\/p>\n
It\u2019s sort of like how fish perceive the ocean as a smooth featureless fluid, even though the water is made of discrete tiny molecules.<\/p>\n
In a sense, Wolfram believes, everything that exists is basically made from space. \u201cPut another way,\u201d he writes, \u201cit\u2019s the exact same hypergraph that\u2019s giving us the structure of space, and everything that exists in space.\u201d<\/p>\n
It almost sounds like theoretical physicists should close up shop and just run some computer simulations using Wolfram\u2019s rules. But as he acknowledges, the job isn\u2019t done yet. So far Wolfram\u2019s project has identified almost 1,000 rules that produce complicated structures that look like a universe. It remains to be seen what rule produces precisely the universe we all actually inhabit.<\/p>\n
\u201cSometime \u2014 I hope soon \u2014 there might just be a rule \u2026 that has all the right properties, and that we\u2019ll slowly discover that, yes, this is it \u2014 our universe finally decoded,\u201d Wolfram writes.<\/p>\n
In his summary, Wolfram declares that hypergraphs illustrate a principle he calls \u201ccausal invariance.\u201d That means that various distinct paths through the hypergraph can sometimes converge. Such convergences allow the cause-and-effect chain of events through time to be preserved.<\/p>\n
In a hypergraph \u201cthere is not just one path of time; there are many paths, and many \u2018histories,\u2019\u201d Wolfram writes. But one supposedly independent path of history can merge with another. \u201cEven when the paths of history that are followed are different, these causal relationships can end up being the same \u2014 and that in effect, to an observer embedded in the system, there is still just a single thread of time.\u201d<\/p>\n
Thanks to causal invariance, Wolfram\u2019s hypergraphs reproduce many of the consequences of various physical theories, such as Einstein\u2019s special theory of relativity. Traveling rapidly slows down time (as special relativity says) because hypergraph structures corresponding to moving objects make an angle through the hypergraph that extends the distance between updates (or time steps). The speed of light is a maximum velocity, as relativity states, because it represents the maximum rate that information can spread through the hypergraph as it updates. And gravity \u2014 described by Einstein\u2019s general theory of relativity \u2014 emerges in the relationship between features in the hypergraph that can be interpreted as matter particles. (Particles would be small sets of linked points that persist as the hypergraph updates, something like \u201clittle lumps of space\u201d with special properties.)<\/p>\n
In an even more complicated extension of these ideas, Wolfram explores how hypergraph properties even correspond to the weird features of quantum mechanics. \u201cIn our models, quantum mechanics is not just possible; it\u2019s absolutely inevitable,\u201d Wolfram asserts.<\/p>\n
Space as constructed in such hypergraphs can have a very fine structure, like a digital camera sensor with gazillions of megapixels. Wolfram estimates that a hypergraph corresponding to today\u2019s universe might have applied 10500 time steps (incomprehensibly more than the universe\u2019s age in seconds, roughly 1015). So space could be fine-grained enough to contain matter-particle structures much, much smaller than the known particles of physics. In fact, Wolfram suggests, supersmall unknown particles, which he calls oligons, might have been created in abundance shortly after the beginning of the universe. Such oligons, subject only to gravity, could now be hanging out in and around galaxies utterly unnoticed \u2014 except for their gravitational impact. Oligons might therefore explain why astronomers infer the existence of vast amounts of invisible \u201cdark matter\u201d in space. (And that could also explain why attempts so far to identify the nature of dark matter have been unsuccessful.)<\/p>\n
Similarly, the mysterious \u201cdark energy\u201d that drives the universe to expand at an accelerating rate might just be a natural feature of Wolfram\u2019s hypergraphs. Perhaps dark energy might in essence just be what space itself is made of.<\/p>\n
Beyond that, Wolfram believes that his hypergraphs could resolve current disputes about which of many speculative theories are the best bets for explaining fundamental physics. Superstring theory, loop quantum gravity, causal sets and other ideas have all been proposed, and debated, for decades. Wolfram thinks hypergraphs can contain all of them.<\/p>\n
\u201cIt almost seems like everyone has been right all along,\u201d he writes, \u201cand it just takes adding a new substrate to see how it all fits together.\u201d<\/p>\n
Wolfram\u2019s technical paper (and accompanying papers \u2014 here and here \u2014 by colleague Jonathan Gorard) have been posted on a website promoting his project, and Wolfram is inviting the physics community to participate in pursuing his vision.<\/p>\n
\u201cIn the end our goal must be to build a bridge that connects our models to existing knowledge about physics,\u201d he writes. \u201cI am extremely optimistic that we are finally on the right track\u201d toward finding the \u201cright\u201d rule for our universe.<\/p>\n
That \u201cright rule\u201d would generate a hypergraph with our universe\u2019s precise properties: three (apparent) dimensions of space, the right cosmic expansion rate, the right repertoire of elementary particles with the correct charges and masses, and other features.<\/p>\n
But perhaps, Wolfram has realized, seeking one single rule misses a bigger point. Maybe the universe uses all the possible rules. Then all the possible universes are just parts of one really big universe, in which \u201cabsolutely everything \u2026 can happen \u2014 including all events for all possible rules.\u201d<\/p>\n
We discern a certain set of physical laws based on the \u201clanguage\u201d we use to describe and comprehend the world. The elements of this language are tuned to \u201cthe kinds of things our senses detect, our measuring devices measure, and our existing physics describes.\u201d The right rule is the one that corresponds to the portion of the hypergraph that we explore from our own particular frame of reference. Life elsewhere might see things differently. \u201cThere\u2019s actually an almost infinite diversity of different ways to describe and experience our universe,\u201d Wolfram suggests.<\/p>\n
In other words, explaining the physics that applies to our existence might require insight into the mechanisms of a vastly more complex reality, beyond the realm of what we can experience. As Wolfram puts it, \u201cIn many ways, we are inevitably skating at the edge of what humans can understand.\u201d<\/p>\n
As he acknowledges, much more work will be needed to merge his approach with the successful theories of established physics. And standard physics does have an impressive resume of accomplishments, explaining details about everything from the innards of atoms to the architecture of the universe and the nature of space and time.<\/p>\n
Yet mainstream physicists have long suspected that space and time cannot be fundamental concepts. Rather it seems likely that space and time are conventions that must emerge from something deeper. It might be a long shot, but just maybe Wolfram has perceived a path that leads to the depths where reality originates.<\/p>\n
Only time \u2014 or many more hypergraph updating steps \u2014 will tell.<\/p>\n","protected":false},"excerpt":{"rendered":"
A computer visualization depicts a \u201chypergraph\u201d consisting of relationships between points constructed by repeatedly applying a simple rule for expanding, or \u201cupdating,\u201d the network. Stephen Wolfram believes a massively complex hypergraph could represent all of physical space and its contents, a clue to finding the fundamental theory of physics.<\/p>\n
COURTESY OF WOLFRAM RESEARCH<\/p>\n","protected":false},"author":1,"featured_media":2151,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[27],"tags":[236,13],"class_list":["post-2141","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science","tag-physics","tag-science"],"acf":[],"yoast_head":"\n