I was reading recently that carbon buckyballs, which are relatively large objects, atomically speaking, behave in a quantum fashion and act like waves when used with the two-slit experiment. These are, I think, the largest objects to date that have been observed to follow quantum behavior. What is the smallest object that has NOT shown quantum behavior? How well-known is the boundary between objects that behave like waves and those that are firmly particles (golf balls? BBs? grains of sand?), using the two-slit experiment as the arbiter.
Not well defined at all. Where the “boundary” lies between classical and quantum depends on the situation, and isn’t even strictly speaking size dependant at all. Really all that matters is the size of the angular momentum or action associated with a system, and there’s no limit on the physical dimensions or mass of a system with a given angular momentum.
There may not be a boundary at all. All objects should show wave character and they have shown it in molecules containing 100 atoms. The problem is that for larger objects there may be no way of demonstrating the behaviour.
If you accept the many worlds quantum interpretation then there is definitely no boundary or observer effect.
Depends upon what you men by “largest object to follow quantum behavior” Some crystal features are arguably quantum mechanical. Some scattering effects have quantum features. Does the Mossbauer effect count?
Most of the time it depends upon how large an effect you are looking for, too, and whether other factors of a large system would tend to blur out small-scale effects. But if, for instance, the blurring is due to thermal vibrations, you can cool your system down to the point where these effects are small enough.
This supposed “boundary” is due to quantum decoherence, which is essentially the interference between the probability waveforms of multiple particles. Once you get a system of particles sufficient to be useful in the real world, i.e. something large enough to look at with light, you generally have a system in which the distribution of probability density above a certain level is much, much smaller than the physical size of the system itself; hence, it is no longer coherent as a quantum system and “classical” mechanics dominates. You can imagine this in terms of raindrops on a pond; one drop will create a very definite radial waveform, and two drops will create identifiable interference patterns. But when you get a whole bunch of drops at once all you see are splashes and a rough, decoherent surface without any discernible pattern at all.
Now, if all the rain were to fall in a synchronized fashion in a geometrically regular pattern you would be able to see a resulting pattern. Similarly, if you create a large completely regular system (like a C60 atom or a Bose-Einstein condensate) you can observe the structure to behave along the probability lines of quantum mechanics. However, outside of these very rare and difficult to achieve exceptions, most systems have a level of disorder is such that the probabilistic nature of matter is lost in the noise.
This doesn’t mean that quantum effects aren’t observable, and while you can get along quite nicely in most fields of engineering and even many areas of physics without explicitly acknowledging that quantum mechanics even exists, there are certainly ways to observe the effects of quantum phenomena on the every day scale. Aside from the double slit experiment, you also have quantum tunneling and the Josephson effect, the alignment of atomic spin in nuclear magnetic resonance imaging, and of course the famous photoelectric effect for which Big Al won his Nobel Prize. Quantum mechanics is going to become critical to advances in computing power and data storage as well as cryptography in the near future.
So, in short, there is no “boundary” between the level at which quantum phenomena with their predictable distribution dominate and that at which classical laws apply; just a further and further blurring of the probabilistic behavior of systems to the point where they are just amorphous, stochastic systems. They are no objects that are “firmly particles,” and the idea that there is a breakpoint between quantum and classical is the result of incomplete or improper teaching of the essential concepts. Classical mechanics is always an approximation of real behavior, albeit one that is entirely suitable and indistinguishable in result (and far, far easier to actually apply) for systems on the scale of real world objects, even very tiny ones.
Stranger
Schrodingers lolCat can has life?
Irish physicist John Stewart Bell restated the Schrödinger’s cat gedankenexperiment in terms of the cat being hungry or not hungry (the decay activating a contraption that would open a can of cat food). Og bless the Irish.
Stranger
I am using the double slit experiment as a benchmark. I’m wondering what is the smallest object to NOT exhibit wave-like behavior in that situation. Carbon buckyballs do. Clearly, say,golf balls do not. So somewhere in between the two there should logically be an observable limit, no?