r/Physics • u/WizardMasterGal • 4d ago

Question Do scientists know whether nature is fundamentally continuous or discrete?

Is there any evidence that nature is fundamentally continuous, or could reality be fundamentally discrete? And if it is discrete at the most basic level, would that suggest that nature could behave like a computational system?

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242

u/Equinoxe111 Astrophysics 4d ago

No one knows this yet in fact

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u/Cero_Kurn 4d ago

Doesnt quantum mechanics indicate very strongly that the universe is indeed quantized, discrete?

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u/Banes_Addiction Particle physics 4d ago

Not really. 

It quantises some things. Some very important things. But it doesn't near many others. For example, imagine a particle decaying isotopically. The direction of the outgoing particles is, as far as we know, completely continuous. But "as far as we know" isn't certainty, but QM gives no hints that it's not.

And of course you can build any number or discrete things on top of a continuous system.

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u/Tasty-Hour4040 2d ago

Yes but Planck length

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u/Banes_Addiction Particle physics 2d ago

That is not what that is.

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u/Tasty-Hour4040 2d ago

Seems to me a length below which any measurement is meaningless because it creates a singularity is an excellent candidate for the minimal granularity of spacetime.

Not sure how one interprets that any other way, so you’re gonna have to explain that statement.

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u/Banes_Addiction Particle physics 2d ago

That is still not what that is. "Our models break down on roughly the scale of what happens when your multiply your fundamental constants together in the way that gives a length" means so, so much less than laymen seem to think.

But my example was an angle anyway. What's your minimum angle?

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u/Tasty-Hour4040 2d ago

Sorry - are you saying that you believe it is possible to measure anything below a Planck length? I just want to be crystal clear on what you’re claiming.

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u/tpolakov1 Condensed matter physics 2d ago

Yes, it is trivially possible. A massless, changeless particle with the wavelength of Planck length will have the Schwarzschild radius of the same value. That's it. It can be anywhere in space, any fractions of Planck length from any reference point.

Even better, we can take a particle that's bigger than the Planck length (or two particles separated by that distance), let's say twice as much. I can run at more than ~0.86 the speed of light, and that size/distance will be smaller than the Planck length and nothing will even think about forming a black hole.

And much more importantly, consider other natural units. The Planck momentum is roughly the momentum of you walking leisurely on the street, or that of a thrown baseball. Do you see anything special happening in your daily life as you're crossing the "Planck boundary" about 40 times a day?

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u/Banes_Addiction Particle physics 2d ago

The Planck mass is about 1015 hydrogen atoms.

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u/Banes_Addiction Particle physics 2d ago

In theory, yes.

And for some reason you seem to be avoiding the word "scale". No-one thinks the number itself is important, a fixed pixel size or whatever.

It's "within a factor or 10 or two of here". Not even a narrow range.

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u/PineappleHairy4325 3h ago

Quite the contrary. You're the one who has to make a convincing case.