Krdytkyu

From what I know about the Heisenberg Uncertainty Principle, one of its consequences is that when you learn a great deal about the position of a particle, you greatly increase the uncertainty of the particle's momentum. This got me thinking about a super-accurate scanner that will measure the positions of all the particles in an object (for example a building) to an extremely high degree of certainty. This would cause the momentum of all of these particles to become extremely uncertain. I am not sure where the energy would come from for this, but if the numbers are extreme enough, most of the particles should have extremely high momentums in random directions, causing the object to be obliterated.

Is my understating of the uncertainty principle horribly flawed, or does this have enough reasonableness for a science-fiction super villain weapon?

I am not sure where the energy would come from for this

It would come from the scanner itself. In order to make extremely-high-precision scans, the scanner itself has to direct considerable energy at the target of the scan. The more precision you want, the more energy you need to pump into it. Much of that energy is absorbed by the target, which is what would cause the particles to fly apart when scanned.

It should be obvious that, in the real world, it would be much easier to build a device (let's call it a "disintegration ray") which just hits the target with all that energy and scatters its constituent particles to the wind without bothering to also determine and record the original positions of the particles. Building a machine gun is easier than building a machine gun which also tracks where its bullets end up and uses that to determine what the target originally looked like.

So I'd call it possible, but extremely impractical in real-world terms.

As a supervillain super-weapon, however, I really like it. The concept makes me smile and it's based on technobabble that sounds reasonable if you don't think too hard about it. And aren't those really the most important factors when designing a doomsday weapon?

This "weapon" has already been built. It's called the European X-Ray Free Electron Laser (XFEL), and it's used for super-accurate imaging of molecules.

Point is, whenever the XFEL hits a target molecule, all the electrons are simply blasted away from the molecule, and the more inert rest of atomic nuclei dissolves in a Coulomb-explosion. The scattered X-Rays are used to reconstruct the 3D positions of all the atoms in the instant that the molecule was hit.

This blasting away of the electrons is not by accident: The shorter the wavelength of the photons, the smaller features you can detect, because the change of the photon's momentum is greater. Of course, that change in momentum comes from somewhere, and it's the electron cloud that gets the kick in the opposite direction. So, the quality of the localization is directly related to the uncertainty of momentum after the measurement.

No, your conclusions are wrong.

Heisenberg uncertainty principles states that the uncertainty in the measurement of two conjugate variables, in this case position and momentum, is always higher than a certain value

$$Delta x cdot Delta P_x > h/4 pi$$

Mind that the uncertainty is on the measurement, not on the actual value (whatever "actual" might mean under the assumption of quantum physics).

Particles in macroscopic objects already move randomly in all direction due to thermal agitation, and that does not destroy the object. When you increase the agitation you are just increasing the object temperature, maybe melting it or evaporating it. But it has nothing to do with Heisenberg principle.

Also, citing this other answer:

$h/4 pi = 1.054571726(47)×10^{−34} Js$

All it needs is some algebra to see that a kilogram ball moving at a micron per second and measurement accuracies of the order of a micron will still fulfill the HUP constraint as $h/4 pi$ is a very small number. For classical dimensions $h/4 pi$ is essentially zero and the HUP always holds.

When one goes to dimensions of less than nanometers and masses of the order of molecules then one is in the quantum mechanical regime and can start talking of uncertainties .

You're misunderstanding the Heisenberg Uncertainty Principle, or rather what "measure" means. In order to measure something, we have to interact with it - on the nanoscale this commonly involves bouncing electrons off of the item we're imaging.

A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons.
- Wikipedia

Imagine "imaging" a pool table by analyzing the path the cue ball takes. It'd be trivial to figure out where a ball is - or more accurately was - at the moment of impact. The cost of this is that you've transferred some of the energy of your scanning cue ball into whatever ball you've measured, altering its momentum - you can no longer be certain the ball is at a standstill. The system you're proposing is one that increases uncertainty by deposing large amounts of energy into a target object. In other words, basically every projectile, energy, or nuclear weapon system known to man. The only difference is the word "measure." Attaching a telescope to your death-ray arguably fits the bill.

Rather amusing way to bypass a treaty, don't you think? It's not a planet killing Nicoll-Dyson beam, it's a Planetary Spectral Analyzer.