Monday, August 20, 2012

Quantum Physics And ..... Golf?!

While article like this are often done tongue-in-cheek, I can't help feeling that it also helps to reinforce a tremendous misunderstanding of physics, especially quantum mechanics. What I dislike the most about this type of article is that they pick and choose certain aspects of physics, and then ignores others that could easily nullify the original assertion.

This "science fiction" writer is doing a "what ifs", applying certain aspects of quantum mechanics to see how it would work in the sport of golf. Yes, golf! Let's take a closer look at the  problems with each one of his ideas:

But if the golfer and the ball could somehow be entangled, then every movement the golfer makes would instantly have an effect on the golf ball. The golfer could literally steer the ball in midair.

Remember, quantum physics deals with teeny-weeny, itsy-bitsy particles that are smaller than atoms. Not macroscopic objects like golfers and golf balls.

However, both the golf player and the golf ball are composed of uncounted gazillions of subatomic particles. If it were possible to entangle one of the particles of the golfer's body with one of the particles of the golf ball, then the golfer's contortions would have an instant effect on the flight of the ball.

The body English would work!
No, it would not. Whenever people are using quantum entanglement, they often overlook one extremely important aspect of this phenomenon - the preservation of coherence of all the entangled particles! This is extremely important because in the destruction of the original entanglement is EXTREMELY EASY. In fact, even a single interaction has been shown to destroy the original piece of information! We only need to look at the gymnastics that we had to put a system through to preserve such entanglement and made such measurement - it isn't easy! We have had success with entanglement phenomenon with photons over long distances, because they weakly interact in air, but we certainly do not have a lot of success so far with  particle entanglements over long distances because they tend to interact very, very easily with their environment. So golf ball and golfer being entangled? I don't think so!

In quantum physics there's a phenomenon known as tunneling. An electron, for example, can run into a solid wall and come out the other side, seemingly without drilling its way through the wall or leaving a hole in the wall behind it.

Imagine a situation on a golf course where the golfer's ball had landed in the deep weeds or behind a rock or some trees. It might take several shots to maneuver the ball around such an obstacle and get back onto the fairway.

But if the ball could somehow be made to tunnel the way electrons do, the golfer could aim his shot at the pin and blast away. The ball would approach the obstacle, be it weeds or rock or tree, and come out the other side, free to sail unimpeded toward the green.

It sounds like magic, but that's the way electrons can be made to behave. Would it be impossible to make golf balls tunnel the way electrons do? It could take strokes off the golfer's score.
First, let's call on the inconsistencies in this scenario. If the golf ball can "tunnel" through the weeds or the rock, what is to stop it from tunneling through the ground as well and miss the hole completely? If it goes through things unimpeded, why would the ground be any different? So already he is expecting a law of physics that turns itself on and off on a whim. As someone once said "God is subtle, but not malicious".

The problem with the application of tunneling of macroscopic object is the same as in the previous point. For the entire macroscopic object to tunnel through a barrier, it must be in completely coherence with each other. If not, the probability of one part of the object tunneling through will be different than other parts of the object. An electron, or a quantum particle does not have that problem. We describe the electron using one coherent wavefunction. We can't do that for a golf ball.

We note that in experiments that showed how particles such as buckyballs can undergo quantum interferences, the experiments were done under extreme conditions such as very low temperature. This is to ensure that the entire buckyball are in coherence with each. Introduce thermal effects, and there goes your interference pattern!

An atom can gain energy by absorbing a photon, the basic particle of light. Or the atom can lose energy by emitting a photon.

Now picture a golfer faced with a long putt. If the ball is hit too slowly it won't make it to the cup. If hit too hard, it will go past the cup. Perhaps the ball might skim the rim of the cup and zip away instead of plopping in.

If the golfer could somehow induce the ball to gain energy or lose energy, depending on how the putt's going, the ball could be guided right into the cup every time. All you have to do is figure out how to make the ball gain or lose energy at your command.
This is where one thing does not have anything to do with the other. Induce the ball to gain and lose energy? How is this related to an atom absorbing and losing energy? It seems that this person seems to think he can violate conservation of energy with the golf ball. Unfortunately, even if he could do this, his ball is already busy tunneling its way to the other side of the earth.

Zz.

20 comments:

Ciaran said...

The last point seems to boil down to blowing on the ball to speed it up/slow it down!

ZapperZ said...

Yeah but from a hundred feet away?

Zz.

motaro2022 said...

Hello ZapperZ. I'm a layman but very interested in some particular aspects around quantum mechanics, namely: quantum tunnelling and the reductionist-vs-emergency debate. So, I was really excited to find your blog after I read some of your posts in Physicsforum and I am glad to have the opportunity to ask you personally. OK, object such as a ball cannot be described by wave function. But some of my opponents claim tha ball is alternatively by density matrix.. so, they claim that the ball CAN actually tunnel but the probability for such event is non-zero (fantastically, vanishingly small). Also, they point iut that NOBODY has a proof that the ball cannot be mathematically described by wave function. Could you help me with counter-arguments against their two arguments? I can't calm down my mind. They want from me to tell about the exact point (in terms of size/degree of freedom etc.) where tunnelling becomes forbidden/completely impossible due to emergent properties. Help please. I need your opinion about these questions!

ZapperZ said...

Hello motaro2022.

My reply would be that just because one can write a wave function for something, it doesn't mean that it is correct.

I can write a wavefunction for a gazillion particles, but it doesn't mean that it is correct. Instead, I have to use that wavefunction and apply it to various situations that have been verified experimentally. If the result matches these observations, then I have some claim that my wavefunction is valid. This is why, for example, the Landau's Fermi liquid theory is a valid starting point to describe metals, because it matches many of the characteristics of various properties of metals, such as its resistivity as a function of temperature.

The problem with large, macroscopic object is that its various parts are not coherent with one another. That is why a REAL cat is never both dead and alive. The cat cannot be easily described with one, coherent wavefunction because it isn't coherent! So how do you write such a wavefunction?

Once again, just because one can write a wavefunction for something, it doesn't mean it is valid. Benchmark it against observed phenomena and show that they match. Otherwise, what one has is an ornament.

Zz.

motaro2022 said...

Thank you a lot for the reply! Please, allow me some follow-up questions. 1) The probability for quantum tunneling of a real-life "macroscopic" object (e.g. a sand grain) is completely (not just effectively) zero? 2) At what size/degree of freedom/scale the quantum tunneling of an object become forbidden? (Obviously, electrons CAN tunnel; what about atoms, molecules and so on?)

motaro2022 said...

Quantum tunnelling (of subatomic particles) is empirically confirmed phenomenon. Since these are building blocks of the so-called “macroscopic” objects (e.g. sand grains, balls, stones and so on), one can easily hold that “macroscopic” object can quantum tunnel, although the probability for such an event is non-zero (insanely, ultra, mega, fantastically, astonishingly, unimaginably, etc. small). This viewpoint uses a kind of extrapolation and this is perfectly valid line of thought.

However, there is another line of thought (opinion): subatomic particle can quantum tunnel, but the so-called “macroscopic” objects cannot quantum tunnel (emergent property). This view could be perfectly valid, too. At least, how can one disprove it explicitly and beyond any doubt?

It seems to me that nowadays most of the physicists rule out that second line of thought. But what is the empirical evidence for their claim?

Of course, that second line of thought suggests that there is a kind of mysterious transition between "quantum" and "classical". However, Nature is not under an obligation to give us clear and definite answers, which satisfy our endless hunger for knowledge and explanations. Nature is not under an obligation to work in accordance with the principle of “economy of concepts”.

Regarding the question in the title, we end up before the following difficulty: the predictions of the both viewpoints are effectively identical. Let me illustrate it:

If you calculate that you have a chance of 10^(-23451234) to 1 to have a ball tunnel through the wall, and you say that you've never seen it happening (and you've tried maybe, 10^(12345) times only), then there is PERFECT AGREEMENT between prediction and experiment so far. So the first viewpoint is experimentally verified.

If you take the second viewpoint and you say that, given that the ball is a macroscopic, and hence, classical object, it CANNOT tunnel through the wall, and you've tested that 10^(12345) times, then you ALSO conclude, that this is experimentally verified.

ZapperZ said...

Let me ask you this. Take a vase that has been smashed into thousand of pieces. Now throw those pieces onto the floor. What are the odds that it will fall just right that it reassemble itself back into the original vase?

No one in his/her right mind would consider this as a reasonable possibility. In fact, most rational people will say that this does not happen, and history has shown us that it HASN'T been shown to have happened. But yet, statistically, it isn't zero! But does that mean that it can and will happen?

What is the gravitational force from Alpha Centauri? For every practical measurement that we make here on Earth, the gravitational force from Alpha Centauri has NEVER been considered, nor is it a fact in anything that we do. Yet, it is still non-zero! But is it rational to keep harping that just because physics says that it is non-zero that it must be considered in every single calculations that we make?

I will once again reiterate that just because someone can come up with a theoretical description, it doesn't make it correct. Without experimental evidence, it is simply a belief. And the one who is proposing it is the person responsible for providing the evidence, not the other way around, i.e. it is not the responsibility of other people to prove that idea wrong.

Zz.

motaro2022 said...

I really appreciate your further explanations and details. As I said, I am completely layman in the topic, so I cannot give relevant scientific argumentation. However, I believe that atoms, molecules and macroscopic objects are fundamentally incapable of tunnelling. So, it is fundamentally meaningless to even calculate and mathematically speculate about the non-zero probability. We have never observed an atom to quantum tunnel. Only subatomic particles: electrons and protons. Yet, quantum fundamentalists claim that I am wrong because I cannot prove that macroscopic objects have emergent property which COMPLETELY prevents them from tunnelling. So, they are insisting again and again on the mathematically derived non-zero probability. However, I think that they cannot prove their belief, just like I cannot prove my opinion. It's just that their astronomically small probability is untrstable. So, it is Belief vs Belief. A matter of opinion. Do you agree?

ZapperZ said...

But what about experimental evidence?

It seems that the people you are in contact with don't seem to think that validating their ideas with experimental observation is necessary. Have you ever asked this to them? Because if this is their take on how we do science, then the conversation should stop right there! They are not doing science, but practicing some form of a religion.

I did my PhD in tunneling spectroscopy in high-Tc superconductors. I do mainly single-electron tunneling. In a few cases, I did what is called Josephson tunneling, in which two electrons that make up a Cooper pair tunneling across the barrier.

However, here's the caveat - the two electrons that tunneled across are in a COHERENT STATE with one another!

This is related to what I said earlier about macroscopic object, i.e. the inability for the the entire object to be in a single, coherent state. It is not the size, but rather the ability to get the entire object to be coherent. I don't see how this can be done. It is already difficult enough to do this with two electrons, i.e. they have to be in a superconducting state before this would even occur!

I wish people who would claim such a thing would get out of their houses and go do a few experiments already.

Zz.

motaro2022 said...

The experimental observations actually are in accordance their claim: in the "wings", the probability is so astonishingly small that it will never happen in the age of the Universe. Is their claim effectively untestable? For sure! Is their claim correct or not? We don't know! Personally, I don't like tge concept of "effectively zero". I don't find it rigourously scientific: at WHAT point we consider a certain probability as "effectively zero"? Obviously, it is not well defined concept. On the other hand, I strongly appreciate your insisting on empirical confirmation. Quantum tunneling of subatomic particles happens on a daily basis in the cores of the stars (of course, under very extreme conditions, high temperatures). It happens also in the SSD devices (under not so extreme conditions). Also, you are not claiming that tunnelling of macroscopic objects is forbidden by quantum mechanics.. at least, it seems to me so, as far as I can understand. By the way, could you please point out for me physicists (even if not mainstream) who actually claim that quantum tunneling if macroscopic objects is forbidden (completely zero, impossible)? I will be very interested to read such papers, if they exist in the scientific world....

ZapperZ said...

I don't know of any such papers or physicists.

On the other hand, you might want to ask the same thing of "them", i.e. if the experimental evidence are in the "wings", then there should have already be theoretical development to show that such a thing can be reasonably measured (notice I wrote "reasonably"). Ask them for such a publication.

Other than that, I consider this to be a waste of time.

Zz.

motaro2022 said...

However, let's consider a solid. A piece of metal or a piece of wood - it doesn't really matter, just a regular solid at room temperature. Some people are telling me that there's non-zero probbaility (very small) for a subatomic particle in the solid to completely "escape" from the solid due to quantum tunnelling. Can really the particle escape the binding forces of the solid? In my humble opinion, this is completely impossible because tunnelling is only between states with the same energy. The final state of the particle outside of the solid would have very high energy and that is violation of the conservation of energy. Or maybe my argumentation is wrong? Could you please elaborate a little but your opinion about the given scenario...

ZapperZ said...

Look up "field emission". This is a common phenomenon due to tunneling.

Z.

motaro2022 said...

ZapperZ, theoretically, does a "macroscopic" object (prepared in coherent state) have the same probability for quantum tunnelling (through a given potential barrier) as an electron?

ZapperZ said...

The tunneling probability depends on mass. In fact, it decreases with increasing mass. A macroscopic object is definitely more massive than an electron.

Another factor to consider. A potential barrier for an electron looks like a potential well for a proton, and vice versa. Already the tunneling probability for, say, a neutral atom is not going to be the same for each component that makes up the atom.

Z.

motaro2022 said...

Zapperz, the debate about quantum tunnelling of "macroscopic" objects (in which I am involved) is getting really heated. There's a guy against me who gave the following argumentation: "A macroscopic object doesn't have to be in coherent state in order to quantum tunnel. The probability for such event is ASTRONOMICALLY small. However, each particle of the object is subject to a tunneling probability and you can certainly calculate the probability of all of them doing it at once. In similar vein, we have NEVER ever observed getting a "6" 10^43 times in a row when rolling a dice, but it doesn't mean it is physically impossible and we can calculate the probability for such event."... So, it seems to me that I am loosing the debate.: it seems that quantum tunneling of "macroscopic" objects IS NOT forbidden by the fundamental laws but just the probability is fantastically small. Please, share your thoughts about the subject one more time.. i really need some arguments on my side. I can't get along with the idea that quantum tunneling of macroscopic objects is possible (although improbable)...

ZapperZ said...

Each particle has a tunneling probability, but their tunneling probability is DIFFERENT from one another.

A potential barrier for an electron looks like a potential WELL for a proton! Same barrier, different probability of tunneling for each of the particle. So how does a hydrogen atom tunnel through the SAME barrier with the SAME probability for each of its constituent?

Zz.

motaro2022 said...

ZapperZ, it seems that not only atom can tunnel through the same barrier, but even a whole trifluoromethyl group. I was brutally tackled with the following article: https://www.chemistryworld.com/news/huge-molecular-fragment-quantum-tunnels-in-everyday-lab-reaction/3008209.article

motaro2022 said...

ZapperZ, quantum tunnelling (of electrons) is often given as an explanation for the leakage current in the p-n junction. Could you, please, help me with a physical explanation for the leakage current without the tunnelling concept? How can it be explained without QM (if that is possible)? Thank you very much!!

ZapperZ said...

Why should it be explained without using tunneling concept when it is a tunneling phenomenon?

Z.