Is Space Pixelated? The Quest for Quantum Gravity
scitechdaily.com
scitechdaily.com
this confirms that i'm ignorant of real physics.
> However, Savage said, there are signatures of resource constraints in present-day simulations that are likely to exist as well in simulations in the distant future, including the imprint of an underlying lattice if one is used to model the space-time continuum.
They did their experiment and did not find anything that would indicate an underlying lattice, but I can't find the paper right now.
[1]: https://www.washington.edu/news/2012/12/10/do-we-live-in-a-c...
basically it's how computers percieve the physical world.
it's also where a lot of theory arises from in neuroscience.
Presumably these devices measure things previously unmeasurable - or at least with as good of accuracy.
I mean, I get that we have hypothesis and have reason to believe nature is going to behave in some way. And then you build the device to measure it, and it comes within some range that's not surprising, and it is inline with previous devices that weren't as accurate.
If you're building a conventional scale - it just seems more reasonable that you can have high confidence and high accuracy because the stuff you're measuring is big enough to physically see and interact with and there's almost limitless things you could use to cross-reference, etc.
Is there an ELI5 for how you can measure things subatomic with ridiculously high accuracy and confidence?
I guess I'm just in complete awe of how this is possible - not doubting that it is.
Similarly, for any "new" measurement, there will be a number of "calibration" measurements performed to ensure that the results are in-line with other measurements of well known things.
In many cases you cannot. Speed and position for example.
You equally, hit limits in human perception and technology/physics limitations more so.
Maybe the universe is always N+1 with N being the best sampling rate known to man. Sure we can infer, but when you want to know the answer to the exact decimal point, sometimes you have to accept that 1/3 is 1/3 and never exactly 0.333333333333 however much recurring you have.
>> 44100khz
> And yet I can flash an LED that fast
This seems unlikely for a number of reasons.
This doesn't mean spacetime is a nice even grid, but it does suggest it comes in discrete lumps of something, even if that something is actually some kind of substrate that holds the information which defines relationships between lumps.
Even if space is continuous, that doesn't mean we can get information in and out of it in infinite precision.
Look at quantum physics. Maxwell's equations don't suggest existence of photons (quantized information). But atoms being atoms, they can only emit and absorb in quanta.
https://en.wikipedia.org/wiki/Decidability_of_first-order_th...
People tend to mentally construct the natural numbers from set theory, wholes from naturals, rationals from wholes, reals from rationals and so on.
But what if there is some universe (in the math sense), which is actually complete and decidable, it's just that the moment you take discrete subsets of it, you also remove the connections that make it consistent or complete.
The very act of formalising mathematical concepts into words and paper is a quantisation step after all, because both are symbols. Maybe there are proofs that can be inuitioned about (assuming brains are continuuous in some sense) but neither verbalised nor formalised.
Presumably this hypothetical universe implements arithmetic, so it’s not complete.
Incompleteness means that there are true statments for which there are no proofs.
But that doesn't preclude proofs that are beyond the proof system that you proofed incompleteness for.
A non discete/symbolic proof might exist after all.
It would therefore not be the existence of the natural number subset that causes undecidability, but the missing parts of the non-natural superset required to talk about the proofs that cause undecidability.
Then the system you are proposing, does it implement arithmetic or not?
But proof by contradiction itself is problematic, because it relies on the law of the excluded middle, which only holds in classical two valued logic.
If you construct math from the top down rather than from the bottom up, then it is natural that it also has a multi valued logic.
In fact, it also would have infinitely valued logic. Infinite sentences, infinite theorems.
Such math is non expressible for us, because we rely on discrete descriptions.
But that doesn't preclude its existence.
Why should it though? What evidence do we have, if we can't express it or fit it into our existing mathematical framework.
To illustrate, think of Goedelsz approach and turn it backwards for a second. Instead of taking predicate logic and assigning each sentence a natural number, imagine that predicate/classical logic is a different view on the natural numbers. Now that means that there might also be logical interpretation of the reals, the hyperreals and so on. (We could do the same with Alephs, in fact they might be the more fundamental objects.)
Perhaps that is exactly what mathematics is? and all it can be? Or perhaps there is a 'higher mathematics' that we cannot reach yet? (or ever?)
At any rate, what does any of this have to do with information capacity in the universe? Is the information capacity of the universe related to the consistency/completeness of arithmetic?
Aren’t you just begging the question by assuming ZFC is consistent to demonstrate that arithmetic is consistent?
Suppose for a moment that it makes sense to say arithmetic is part of the fabric of the universe (whatever that is supposed to mean). How would one know if arithmetic is consistent or complete within the context of being part of the universe? Suppose ZFC is part of the universe. Then arithmetic (the model of it as being part of the universe) is complete and consistent. Now what? I claim nothing of consequence follows from this in relation to whether or not space is continuous.
The same way I know that it’s incomplete when formulated in ZFC (assuming ZFC is consistent), from the first incompleteness theorem.
> Suppose ZFC is part of the universe. Then arithmetic (the model of it as being part of the universe) is complete and consistent.
Why does this conclusion follow?
Are you raising the question of whether mathematical propositions can be justified a posteriori?
Or are you arguing that the incompleteness theorems don’t necessarily apply to theories formulated ‘as part of the universe’?
If ZFC (or some other theory) implements arithmetic, then the first incompleteness theorem says that if ZFC is consistent then there must be true sentences in ZFC (not necessarily sentences of arithmetic) that can’t be proved in ZFC. Correct?
I had two points in these posts. One is that none of this pertains to whether or not space is continuous. The other is that the statement “arithmetic is consistent” is provable in some contexts. It depends on what the actual theory one is dealing with. In PA it’s not provable but in ZFC it is.
If the universe “contains” a model of PA then is that model consistent or not? How does one know? (I doubt it’s meaningful to say that the universe contains PA though.)
To me, “space is continuous” seems like a proposition that must be demonstrated a posteriori and I wouldn’t expect properties of formal systems to serve as evidence for the claim. So I agree.
> The other is that the statement “arithmetic is consistent” is provable in some contexts.
Agreed.
> If the universe “contains” a model of PA then is that model consistent or not? How does one know? (I doubt it’s meaningful to say that the universe contains PA though.)
Okay, yes, how can we interact with or measure PA as implemented by the universe? How do we (or can we) meaningfully talk about the universe implementing PA?
Yes those questions seem interesting to me, but I don’t have anything intelligible to say about them.
I don’t either!
This would be true if objects existed at perfectly local points. However we know that a perfectly localised wavefunction has spatial frequency components that add up to infinite energy. Any wavefunction with finite energy is band-limited. At non-zero temperature the Shannon-Hartley theorem will give a finite bit rate density over frequencies, and since the wavefunction is band limited it will therefore only have the ability to carry a finite amount of information.
The difference is we know what the quantised components of field theory are. We don't have any idea what the quantised components of spacetime are supposed to be, or how they operate.
The various causal propagation theories (like causal dynamical triangulation) may be the first attempts at this, but it's going to be hard to get further without experiments that can probe that level - which is very difficult given the energies involved. Without that, we're just guessing.
Without some smallest resolution, we'd need infinite amounts of information to track point particle displacement in one dimension.
That doesn't mean anything has to be a particular way, but it at least would be intuitively consistent to me.
When I think about that, I wonder if that 'quantization of space' is what determines the speed of light. And perhaps explains why inertial and gravitational mass are identical.
Not according to constructivism it does not.
If I zoom in close on my hand, does it move like a sprite in a 2D video game? Always on a “grid”, with no way to be in between pixels?
There is no compelling evidence to suggest that this is the case, at least down the scales we have been able to zoom into.
I think, "Wait a second! Nothing has 'turned out', because there are no experiments."
So now there will be. I applaud this effort. If something is untestable, then ignorant people who equate "faith in religion" with "faith in science" are right. Let's get some data that can only be explained by Theory X, and then see if Theory X predicts more things that also turn out to be true. If Theory X turns out to be one of the many variations of string theory, then you've got something there.
You don’t need anything as exotic as a black hole, general relativity can’t say anything about how gravity works at small scales at all.
That being said, physicists dislike discontinuities. A theoretical point particle with high mass means that there must be a mechanism to merge large quantities of mass into black hole matter. If it is a point particle with extremely large gravitational fields, these final interactions would also require some version of quantum gravity to predict. In fact, it's entirely plausible that what we observe as black holes are actually not GR singularities at all https://en.wikipedia.org/wiki/Black_hole#Alternatives
There is hope for improving observational data on black hole interiors by measuring the gravitational waves of merging black holes. Different types of black hole singularities will have different event horizon shapes, and the merger of these black holes should produce different gravitational waves, amongst other observable effects. https://en.wikipedia.org/wiki/Kerr_metric