# Is space discrete or continuous?

Or is it still an open question? I know it is often asked question (looking at google results) but I haven’t seen a definite answer…

And this is the question I’ve wanted to know the answer to for years. And so far what I’ve heard is that we don’t know.

Discreet or continuous? Do you mean finite or infinite?

No, he means quantized. We don’t know, but if I had to bet, I’d bet quantized.

Another question: if space was indeed discrete wouldn’t it require that it would have the form of a grid? And if yes, what shape cells of the grid would have?

If it’s discreet it needs to smooth out at larger scales and so that seems to me to imply it must be continuous (i.e. no gaps).

But that doesn’t mean it has to be a periodic regular matrix. It could be aperiodic like penrose tiles. Which raises the question, if you have multiple “spacetime tiles” shapes then light paths could be different depending on which shapes they cross. I suppose over huge distances (million of light years) you could maybe detect that.

Like** John Mace** said, nobody knows. Quantum physics *models everything as discrete, including space, and makes really accurate predictions. The hunch[sup][/sup] is that space is discrete volumes about a Planck length on each side.
*I’m relying on my memory of Brian Greene’s Elegant Universe and Fabric of the Cosmos, and Brian Greene’s hunch being representative of quantum physicists’ collective hunch.

Since we’re all still WAGGING I’ll toss in my guess: We’ll find out that the concepts of discreet and continuous no longer have meaning when we try to look between the quanta.

Still no matter if grid is regular or not there is a problem: say we have an object in some cell and this object has velocity which direction isn’t parallel to any of cell’s “walls”. Which cell does the object move next? Does its path have a form of stairs? Like an aliased line: http://i.imgur.com/8ifhK.png? I mean it’s weird to think that real world objects may move like that…

If I remember correctly, I think I read a blurb this year saying they uncovered some big mathematical difficulties with the quantized model. I tried googling and haven’t found it.

Yes, *and *the particle doesn’t really *move *from one cell to the next. It just stops existing in cell A, and a quantum length of time later, it exists entirely in cell B.

That is, *if *the model is correct in describing ‘reality.’ Some physicists say the question is nonsensical, others don’t.

Energy is quantized. Does this mean that the potential energy of an object can only take discrete values? If so, doesn’t that imply that an object can only exists in certain discrete locations within a gravitational field? If so, does that imply that space is discrete?

Probably all very rudimentary questions, but I’m no physicist.

Is this true that Quantum physics models every thing as discrete? The energy of a photon is not discrete as far as I know. The possible wavelengths of photons is continuous as far as I know. Is this wrong?

Another question: if space-time is discrete does it mean that n-body problem is solvable? I.e. you can predict exact body path through simple iteration? (yeah you can do it anyway but if space-time is continuous you get approximation error inversely proportional to Δt you use. If space-time is discrete then there exist finitely small Δt where there is no error)

I saw some articles that theorized that the universe is a big automaton, a state machine. Kinda like game-of-life but with more complex rules with cells sized on Planck scale.

It would be a great indiscretion indeed if you were to start “looking between the quanta.”

It’s discrete.

Because you’ll never be able to prove me wrong, but could hypothetically be able to prove me right.

And just for those who are confused, this is a pun on the fact that some people are saying “discreet” when they mean “discrete.”

Quantum physics treats spacetime as continuous. In fact, every working theory we have assumes a continuous spacetime.

I wouldn’t answer this question as “nobody knows”. Rather, I’d say that we have no experimental evidence for discrete space, and our best theories so far for making predictions about the world assume continuous space. That doesn’t mean space isn’t discrete. It just means we haven’t seen anything that requires it.

Discrete space shows up in many quantum gravity models, but unfortunately no one has yet come up with a quantum gravity model that gives meaningful predictions.

Funny thing is that in my language both words have the same spelling.