[jeffreyH (OP)]

Can we find a way of treating macroscopic objects in terms of quantum mechanics?

[petelamana]

Great question, a bit paradoxical, I believe.  None-the-less, I'm hopeful that it will inspire meaningful debate.

I have always believed that one critically exclusive characteristic of macroscopic objects lies in our ability to adequately describe them using non-quantum physics/mechanics.  However, isn't everything ultimately a quantum object?

Or, is the question one of bridging the divide between macro and quanta?  In other words, can the queen be characterized, and defined, using quantum theories and still retain her macroscopic identity as the queen?

[Bill S]

Would it be fair to say that a start has been made in that direction? 

E.g. buckeyballs have 60 carbon atoms, so must be considered as macroscopic objects, but they show quantum characteristics in the double slit experiment.

[alancalverd]

The viscosity of liquid helium, superconductivity, semiconductors, and laser action, are all macroscopic examples of quantum effects that cannot be predicted by nonquantum mechanics.

[Bored chemist]

https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate

[evan_au]

There is a theoretical calculation of the wavelength of a massive object.

It has been demonstrated for objects having hundreds of atoms, but in theory it could extend to objects of any mass.

However, when the wavelength of an object is less than the wavelength of the electrons on its surface, there is not much practical impact on macroscopic objects.

See: https://en.wikipedia.org/wiki/Matter_wave#Molecules

[geordief]

Might it be possible to design macroscopic objects that  would exhibit quantum effects  more strongly?


Would there be any point?

[Bill S]

Would there be any point?

I guess that the possibility that it might lead to a better understanding of quantum effects, and the link between the quantum and macroscopic realms, would be point enough.

[geordief]

I guess that the possibility that it might lead to a better understanding of quantum effects, and the link between the quantum and macroscopic realms, would be point enough.

Might it just push the can down the road?

Are quantum  effects still being understood better as time goes on  or is progress being rather attempted along the lines of  quantum gravity and the like?

Do those at the forefront of this area exhibit the bafflement that the public probably does  or are they completely comfortable with the findings and interpretations?

[jeffreyH (OP)]

Say we have a spherical container enclosing a Bose Einstein condensate that is falling freely in a gravitational field towards a dense source. At some point the condensate will experience tidal forces. At this point is it still a condensate?

[jeffreyH (OP)]

http://physicsworld.com/cws/article/news/2010/jun/17/condensate-created-in-freefall
I found the above page. Very interesting!

[petelamana]

Indeed, JeffreyH.  Thank you.  - Pete

[jeffreyH (OP)]

There is also an update.
https://physics.aps.org/articles/v6/23

[puppypower]

The concept of entropy suggests that macroscopic objects are also quantum objects. Entropy is a state variable, meaning for any given state of matter, that state defines a very specific measured amount of entropy. Water at 25C and 1 atmosphere has the same amount of measured entropy, no who measures it. This value of entropy, is a science and engineering standard. It is not random, but a repeatable constant at those exact conditions.

Entropy is a constant for each specific state of matter. This suggest that states of matter are quantum states. However, the quantum states of the macro world, are often very close together, to where they may not appear distinct but appear to blend. The distinctions between quantum states is more obvious in the micro-world.

If we have water at 25.01C and 1 atmosphere the entropy goes up to a new constant. If we use water at 25.00001C and 1 atmosphere, it goes down slightly to new constant, which may not be measurable, to where we could use it as a standard, and say it is a quantum state. Conceptually, it has a distinct entropy.

If we look at absolute zero; T=0K, the entropy is at a minimum. Since the second law states that the entropy of the universe needs to increase, we have entropy potential or the potential for higher entropy affects to become induced, like super conductivity, which define higher entropy states. These can appear more distinct and look more like quanta.

Information entropy is another definition for entropy. This definition is often confused to mean the same thing as matter based. The main difference is, information entropy is not a state variable. I can't take a certain number and variety of words and make them always say the same thing, for a given set of conditions. Words are subjective.  For example, If you say something mean to someone, you may not be able to reach the previous state of conversation, before the words were spoken. The measured entropy may be higher even saying the same things; tension. The information definition of entropy is more about loss and random, since this is not a state variable. This definition tends to preclude a quantum argument. This seems reasonable due to the closeness of macro-states of distinct entropy.

[chiralSPO]

Entropy is a concept out of thermodynamics, not quantum theory. That it is a state function has no bearing on whether it involves "quantum states" or not. Entropy can be (and was) derived using entirely classical mathematics.

[Bored chemist]

Entropy is a state variable, meaning for any given state of matter, that state defines a very specific measured amount of entropy. Water at 25C and 1 atmosphere has the same amount of measured entropy, no who measures it. This value of entropy, is a science and engineering standard. It is not random, but a repeatable constant at those exact conditions.

You could say the same about density or refractive index.
So what?
It has, as Chiral pointed out, nothing much to do with QM.


However, imaging I get a gold block the size of a house.
Most people would say that's macroscopic; they would also say its a yellowy colour.
The colour of gold is a quantum effect.

[chiralSPO]

It looks like people have been addressing this question in two different valid ways. There are macroscopic objects or devices that have properties that can only be explained using quantum mechanics, but most of these phenomena occur at a very small scale (subatomic to dozens of atoms), and only the concerted action of many small regions behaving in quantum "oddness" delivers the macroscopically observed phenomenon. Actually, in addition to all of the exciting examples provided, like lasers and superconductors and superfluids, basically every boring attribute of a material we can think of can be traced to quantum effects. Why is iron magnetic? Why is copper conductive? Why doesn't helium form stable compounds? Why is water colorless? Why is potassium permanganate intensely purple? Why does propane burn in oxygen? etc. etc. etc.

All chemical and electronic properties, and all the interactions between light and matter ultimately require a QM treatment of the components of species involved at a subatomic level.

Then there are those who have offered examples of ensembles of atoms of ever-increasing size that still behave as a system in a way that we could treat as a "particle" with QM properties. I think the largest claim I say in this thread concerns the wave-particle duality of buckyballs (C₆₀  molecules). This has been experimentally verified, and has even been extended to much larger molecules, over ten times as big (https://medium.com/the-physics-arxiv-blog/physicists-smash-record-for-wave-particle-duality-462c39db8e7b).

I will also add that in addition to the de Broglie wavelength, which contracts with "particles" having greater momentum, there is a purely probabilistic reason that we do not see macroscopic versions of QM like lab rats "tunneling" through walls. Let us imagine for a moment, that there is a small flea pressed right up against a 1 mm-thick piece of glass, and that each atom in the flea has a one in a billion chance (10^–9 of "tunneling" through the glass in a given second (the chances are actually much smaller, but still nonzero). The flea is composed of about 10¹⁹ atoms, so even though the chances are so small for any given atom to appear on the other side of the glass for a moment, because of the large number of atoms, we would expect (again, in this unrealistic scenario) about one billionth of the atoms to be on the other side of the glass at any point in time, which is still about 10 billion atoms! (10¹⁹ × 10^–9 = 10¹⁰ atoms). But, if we want to know what are the chances of the whole flea appearing on the other side of the glass, we find that number to be so vanishingly close to zero, that we can even discount it from ever happening in the ridiculously inflated example. (1–10^–9)⁽¹⁰¹⁹⁾ < 10^–40 The universe is only about 10¹⁷ seconds old, so you would expect to wait 10²³ times the age of the universe before the flea could escape.

[chiralSPO]

so you would expect to wait 10²³ times the age of the universe before the flea could escape.

Oh, and by that point, not only would the flea have died of old age, but it is much more likely that a significant chunk of the flea would have tunneled through before the whole body had a chance... ouch!

[opportunity]

Is this subject along the lines of fractals? Stepping up atomic phenomena to the large scale while holding the fundamental modus-operandi pattern/shape, while considering the ideas of general and special relativity in that step-up process from the atomic level?

Or, on another angle, is not cosmological phenomena tied closely to quantum logistics, as per quantum cosmology? This is all about therefore tying relativity theory with quantum theory. I'm not sure if fractals can help there with current mechanisms of theory?

As a suggestion, it seems we need to dive into sub elementary-particle levels, re-consider a-priori ideas/definitions of time and space for instance, to resolve quantum mechanics and relativity if the step-up process doesn't work (and thus try the step-down process, the sub elementary particle level?). There are other possibilities of course.