Digital physics

[FlatAssembler]

So, what do people on this forum think about digital physics? To me it seems like a very plausible hypothesis about the nature of the universe. Assuming that time and space are made of pixels basically solves the Zeno's paradox.

[Alex K]

So, what do people on this forum think about digital physics? To me it seems like a very plausible hypothesis about the nature of the universe. Assuming that time and space are made of pixels basically solves the Zeno's paradox.

Nature could be that way , and mathematically it would have some nice and tidy aspects to it if space (and time) were made up of pixels, because all the infinities that plague the mathematics of quantum theory would be absent. Movement from one place to the next would then simply be your wave function on one pixel leaking into the next pixel via some kind of next-neighbor interaction.
However, there are some aspects in the laws of nature, especially relativity, that let me think that things are not that simple though. Fundamentally, relativity does not distinguish frames of reference, i.e. the laws of physics seem to be exactly the same no matter whether you move at some speed - but your pixels are resting in one particular frame of reference and therefore give us a unique fixed rest frame. In the known laws of relativity, there is no such absolute rest frame. Also, a square lattice of pixels has special directions in space along which it is aligned, but what we observe is that the laws of nature are very exactly independent of the direction in space, what is called rotational invariance.

All that means that Nature somehow would have to hide from us the fact that microsopically, there is an absolute notion of direction, and of resting or movement, but at long distance scales this somehow averages out and becomes irrelevant. Technically speaking, one would call that an accidental symmetry which arises even though it is not in the fundamental laws of nature. I hesitate to accept fundamental laws of nature which have less symmetry than what we observe. In most examples, it is exactly the other way around, for example with the Higgs field which hides symmetries from us which are actually there in nature if you look closely, so exactly backwards from what you propose.

But whether I like it or not aesthetically, it is quite possible that such an enhancement of symmetry occurs: for example, when you fashion a round ball out of steel, you don't see at first glance that the crystal lattice in the steel has a particular alignment in one direction, because the ball just appears round. Only when you look very closely at the structure, or shoot X-Rays at it and let them refract, do you immediately see it. Maybe nature is like that as well, but the symmetries of relativity are so exactly preserved... I would at least expect to see traces of your grid in the Cosmic Microwave Background which comes from fluctuations that were once at subatomic scales.

This matter of symmetry is even more egregious when we go to gravity and General Relativity, because now we have a theory in which space and time can bend and distort in any shape and form. This theory again has a huge amount of symmetry because it allows the completely free bending of space and coordinates, which again seems at odds with a fixed grid of pixels which does not exhibit such a symmetry.

One more thing: as people who simulate the strong interaction of quarks and gluons on pixels in supercomputers (called "Lattice" field theory) can tell you, it is not straightforward to have particles with half-spin such as quarks or electrons on a discrete pixel grid because when you try to put the Dirac equation onto a discrete lattice, you get weird effects such as mirror particles which are not there in nature.

All that is just a matter of weighing mathematical hints to assess whether the proposal is plausible, but Nature doesn't care what we think and often holds implausible things in store for us. It's just that to me, Nature at the scales we can observe doesn't really look like it has a rigid pixel grid underneath. I don't think Zeno's paradox is much of a paradox. At least it doesn't lead to serious problems on the mathematical side of things, that's why Newton and Leibniz invented Calculus, to describe continuous motion. It seems to work allright.

[brewer]

Learn something new every day. Thanks guys.

[ignoramus]

Learn something new every day. Thanks guys.

Same here MH.
You know them camels you were wondering about? Apparently they will deliver them from Amazon?

[FlatAssembler]

I've been listening only to Stephen Wolfram (a theoretical physicist who is, along with the Nobel-prize-winning physicist Gerard 't Hooft, the main proponent of the digital physics) about this, so I haven't really heard both sides of the story. I find it comforting to believe that our world could be just a computer simulation.

[bennyboy]

I've often said this, and been generally mocked for it. But it comes from my own experience in calculating gravity values in gaming. My theory should, if I sit down and do the math properly, show how BIG the "pixels" are, or how long time "ticks" would need to be to avoid breaking the system.

The scenario is a simple one: calculating the acceleration of objects as they move very close to a gravity source (say, a planet), with everything being calculated say every 1/30th of a second. With slow-moving objects, this is no problem: when a spaceship approached a planet, for example, you'd get a collision, calculate the angle of impact, and deflect (or just explode) the ship. BUT when the spaceship started moving too quickly, a tick of say 1/30th of a second could easily take it from outside the boundary of a planet to a position very near the planet's core, or in some cases, the ship would actually pass THROUGH the planet, because its velocity was more than 30x greater than the width of the planet. In this case, you might not even trigger a collision!

Things got worse when I allowed the user to place gravity singularities in space, with the idea that you could manipulate the movement of planets or other objects in interesting ways. The problem was that with a singularity, there is NO collision unless the spaceship or whatever actually moves into a position where the singularity is inside it. The result: since acceleration due to gravity is calculated as a function of 1/R^2, if R = 0, you've crashed your computer. If R is very close to 0, the resultant velocity at the next tick is so great that it cannot be enumerated by a 32-bit float number (or, in theory, a float of any size).

One or more of the following is absolutely required to prevent breaking the program:
1) A continuous time (i.e. not ticks of 1/30th of a second). You have to figure out the paths of objects, and make sure they couldn't have collided any time within that tick length, and then "rewind" time to the collision point to recalculate things.
2) Maximum velocity and minimum sizes: you'd have to guarantee that the spaceship couldn't possibly get close enough to the center of a planet, because the velocity could never be large enough to allow the spaceship to "tunnel" too close to the planet's center of gravity.
3) When introducing a singularity, you must "turn off" its gravity when an object passed to close to it (or moved right through it). In other words: cheat. Make sure that the object is artificially set to be outside the "breaking distance" for the maximum allowed velocity.


If God is a game designer, then you can see what would happen if time was digital: you'd end up with particles sometimes entering too close to the center of gravity of another particle, and then accelerating off into functionally infinite velocity.

[Alex K]

I've been listening only to Stephen Wolfram (a theoretical physicist who is, along with the Nobel-prize-winning physicist Gerard 't Hooft, the main proponent of the digital physics) about this, so I haven't really heard both sides of the story. I find it comforting to believe that our world could be just a computer simulation.

If 't Hooft is in favor of it, it is plausible. He is very smart and understands everything. This is the first I hear about him being serious about spacetime being a fixed lattice, though. I would venture a guess that he is proposing something more involved than that?

[Dropship]

..I find it comforting to believe that our world could be just a computer simulation.

Yes anything's possible..-



Or perhaps our "reality" is just an illusion or dream-
"Reality is merely an illusion, albeit a very persistent one''- Einstein
"All that we see or seem, is but a dream within a dream"- Edgar Allen Poe
"You can be in my dream if i can be in your dream"- Bob Dylan
"We are such stuff as dreams are made on"- The Tempest
"Strawberry Fields...nothing is real"- The Beatles
"What is your life? You are a mist that appears for a little while and then vanishes" - Bible,J ames 4:14
"Have you ever had a dream that you were so sure was real? How would you know the difference between the dream world and the real world?"- Morpheus in The Matrix
"The quantum atoms or elementary particles themselves are not real; they form a world of potentialities or possibilities rather than one of things or facts"– Prof. Werner Heisenberg (Nobel Prize winner in Physics)

We could speculate further and say that Jesus was a 'Master of the Art of Dream Manipulation' which would explain how he was able to perform his 37 miracles (and he said we could do it too).
In that respect, perhaps prayer is a form of "thought pressure" that can influence this fragile dream we call 'reality'?
Oops sorry was I rambling?..

[FlatAssembler]

I've been listening only to Stephen Wolfram (a theoretical physicist who is, along with the Nobel-prize-winning physicist Gerard 't Hooft, the main proponent of the digital physics) about this, so I haven't really heard both sides of the story. I find it comforting to believe that our world could be just a computer simulation.

If 't Hooft is in favor of it, it is plausible. He is very smart and understands everything. This is the first I hear about him being serious about spacetime being a fixed lattice, though. I would venture a guess that he is proposing something more involved than that?

He has written a book called "The Cellular Automaton Interpretation of Quantum Mechanics". I haven't read it though. Again, I've read only about that from Stephen Wolfram.