WHY DOES THE UNIVERSE EXIST?
Stephen Wolfram is trying to find a rule that dictates the Universe. And in doing so, he might even become the first person to finally devise a complete, fundamental theory of physics. Elegant, or what?
Back in the plague year of 1665-1666, Isaac Newton changed the scientific world, discovering the universal law of gravity and the mathematics of calculus. Now, in the plague year of 2020-2021, is history about to repeat itself? Stephen Wolfram thinks so. The British-born scientist, who lives in the US, claims he has found a route to a fundamental theory of physics that answers some of the biggest questions, such as what is space? What is time? And why does the Universe exist?
“To be fair, a lot of the work was done in 2019 and we were about to start speaking about it in March 2020, but everything locked down for COVID,” says Wolfram. “But it is true to say that we have made more progress towards finding a fundamental theory of physics than I dared believe was possible.” Wolfram’s starting point was to ask: What is space? “Physicists don’t often ask this question,” he says. “They merely think of space as the backdrop against which the events of the Universe play out.” According to Wolfram, space is made of a network of ‘nodes’, which are connected to each other. The nature of the connections – how each node is linked to nearby and faraway nodes – can create a space of any dimension. So if the number of nodes increases as the square of the distance from any given node – like the surface area of a sphere – the network has the properties of familiar 3D space. “I actually believe the Universe started out with infinitely many dimensions and gradually cooled down to the three we have today,” says Wolfram. “But I don’t yet know why there are precisely three.”
Wolfram is interested in what is the minimal ‘stuff’ needed to create the Universe. And in addition
to the network of nodes – ‘the atoms of space’ – there is another ingredient, the ‘rules’ that change the network. So, for instance, a rule will say: ‘wherever there is a particular pattern of nodes, replace it with another particular pattern of nodes’.
“It is the application of such rules, over and over again – the continual updating of the space network – that knits together space,” says Wolfram. “The miracle is that this process can also create all the matter in the Universe and all laws of physics we have discovered over the past 350 years.”
THE UNIVERSE IN A COMPUTER
Before examining this remarkable claim, it is worth considering how Wolfram got to this point. Born in London in 1959, he was publishing physics papers at the age of 15. As a graduate student at the California Institute of Technology in Pasadena, he worked with Richard Feynman, arguably the most notable post-war US physicist. But a crucial event for Wolfram was a discovery he made in 1981 when he used a computer to investigate the consequences of simple computer programs – ones whose output is repeatedly fed back in as their input, like a snake eating its own tail.
The simplest computer programs he could think of at the time were cellular automata. These are one-dimensional lines of squares, each of which can be empty or filled. A rule is applied that replaces a certain pattern of squares with another. In this way, a new line of squares is created. And another new line. And so on.
Most of the time Wolfram found that nothing interesting happened. In some cases, however, there were persistent features that moved across the evolving cellular grid, reminiscent of subatomic particles in the real world. But the big surprise was that there were a few rules that created neverending novelty and complexity. This was a light bulb moment for Wolfram. Usually, simple programs have simple outputs and complex programs have complex outputs. But Wolfram had discovered simple programs with complex outputs. His immediate thought was, “Is this how the Universe creates a rose or a newborn baby or a galaxy? Is it merely applying a simple program over and over again?”
In 2002, Wolfram published A New Kind Of Science, a 1,200-page tome with 1,000 black-and-white pictures and half a million words. In it, among other things, he explored the consequences of all 256 possible rules for onedimensional cellular automata, among which was Rule 30, which generated unlimited complexity. The book was met with hostility from the physics community. Partly, it was because he had published it himself without going through the usual peer review process. But another reason was that other physicists could not see how to use his ideas to predict anything useful.
They had a point. Basically, Wolfram was saying that most of what the Universe is doing is ‘computationally irreducible’ – that is, the outcome can be discovered only by running the computer program for the 13.82 billion years the Universe has been in existence. To many other physicists that was a fat lot of good.
But Wolfram was also saying that, within the Universe generating computation, there are ‘computationally reducible’ islands, where it is possible to deduce the outcome without actually running the program. “These shortcuts are none other than the laws of physics we have discovered,” says Wolfram.
In the end, Wolfram did not pursue the ideas he had laid out in
"THIS PROCESS CAN CREATE ALL THE MATTER IN THE UNIVERSE AND ALL LAWS OF PHYSICS”