Throwing a tennis ball through a wall

[Haelfix]

As I understand quantum mechanics, my answer would be that indeed it is possible for a book to tunnel through a table. Just that the odds of this happening are like 10^10^10^10^10^10^...^10^-(some large number). So astronomically small relative to the timescales of both the universe and myriad other events from occurring, that its essentially for all physical purposes zero.

When I was taking my competency exam in grad school, one of the past questions was to derive an order of magnitude estimate for a molecule of hydrogen sitting on a table to tunnel through a 1 fm graphene wall with some given density. The accepted answer was ridiculously tiny, but also a notoriously controversial question b/c depending on what effects you take into account (eg what potential wall do you want to ansatz), the answer changes by hundreds of orders of magnitude!

 

[bjacoby]

As I understand quantum mechanics, my answer would be that indeed it is possible for a book to tunnel through a table. Just that the odds of this happening are like 10^10^10^10^10^10^...^10^-(some large number). So astronomically small relative to the timescales of both the universe and myriad other events from occurring, that its essentially for all physical purposes zero.

When I was taking my competency exam in grad school, one of the past questions was to derive an order of magnitude estimate for a molecule of hydrogen sitting on a table to tunnel through a 1 fm graphene wall with some given density. The accepted answer was ridiculously tiny, but also a notoriously controversial question b/c depending on what effects you take into account (eg what potential wall do you want to ansatz), the answer changes by hundreds of orders of magnitude!

Your answer, though reflective of common physics assertions, simply shows how far physics has moved away from science and toward magic and mysticism. Part of the problem is that mathematics has become worshiped as a substitute for science. Mathematics is regarded as more real than reality. Physicists commonly talk about fields and point charges and imaginary numbers as if these things actually has some real meaning in a physical world. Sorry mathematics is abstract. It does not need to agree with experiment. It only needs to be some self-consistent mental concoction.

So given such a mindset, we find hideous statements being passed off as physics. These include the mathematical extensions of QM such as tennis balls tunneling through walls and bowling balls being reflected from a table edge. I happen to know a physicist who actually calculated the bowling ball reflection. Sorry. You can roll them at a table edge FOREVER and they'll never ever come back. Why? Because the REAL ACTUAL energy functions at the edge of the table are not the ideal mathematical "wells" and "steps" that are so mathematically convenient. They turn out to be nice smooth falling off curves that could never produce a minor reflection let alone one on a bowling ball. Doubtless the same is equally true for real tennis balls.

So the bottom line is that all these stories of the "weirdness" of QM when transferred to daily life make great fodder to impress a class full of freshmen, but the truth is that it's nothing but Hollywood and just as much fiction as their latest movies. So the tunneling of a tennis ball may be "impossible" according to QM mathematical models, but a real tennis ball is different.

Now the question as to whether or not a tennis ball actually CAN pass through a wall under the right conditions (not simple QM statistical ones) is anther question all together. We do know that a wall is mostly empty space. There are hints (but nothing more) in stories and myths that saints and others can develop such an ability. Is it true or Memorex? Well who knows? Fact is one has to suggest that in some manner (but not a straight quantum mechanical one) it actually MAY be possible for a tennis ball to go through a wall, or the temperature in a room to be lowered, or a bowling ball to be reflected from a table edge. And the reason we must allow this possibility is the rule that says saying some physical phenomenon is "impossible" is the mathematical equivalent of saying "I'm a moron". Mathematics can express impossibility by definition. Physics has no such luxury.

I will leave the proof of this last theorem as an exercise for the interested student.

 

[DrChinese]

As I understand quantum mechanics, my answer would be that indeed it is possible for a book to tunnel through a table. Just that the odds of this happening are like 10^10^10^10^10^10^...^10^-(some large number).

Paraphrasing from the movie Dumb and Dumber:

So there IS a chance that I will end up married to Angelina Jolie...

 

[Greenman]

Note that this thread was 3 years old...

So does everything ZapperZ said 3 years ago still stand today?

 

[Greenman]

Does this mean that a tennis ball COULD INDEED go through a wall:

http://www.sciencedaily.com/releases/2009/09/090923151730.htm

 

[ZapperZ]

Does this mean that a tennis ball COULD INDEED go through a wall:

http://www.sciencedaily.com/releases/2009/09/090923151730.htm

The fact that these are josephson junctions under superconducting conditions means nothing to you? Notice my earlier argument that a tennis ball must have ALL parts of it in coherence with each other for the WHOLE tennis ball to tunnel through. So why do you think people go through all that trouble to do most of these experiments in the superconducting state?! I mean, look at the Delft/Stony Brook's Schrodinger Cat-state experiments. Why did they go through all that trouble to do their experiments in the superconducting state? Do you think they could maintain 10^11 particles in a coherent state if they don't go through such lengths?

Moral of the story: preservation of coherence is NOT EASY! Even after just ONE single interaction, that has been shown to be https://www.physicsforums.com/showpost.php?p=1498616&postcount=55"!

Zz.

 

[Greenman]

Sorry, I didn't mean to imply it was proof, but rather that *perhaps*? it is a good indication that quantum tunneling on objects such as a tennis ball have a nonzero *possibility*

In other words, that this is a step forward in favor of it being at least possible.

But on another note, I don't know if you got to read my message, but what do you think of Takagi's book on Macroscopic Quantum Tunneling?

 

[ZapperZ]

Sorry, I didn't mean to imply it was proof, but rather that *perhaps*? it is a good indication that quantum tunneling on objects such as a tennis ball have a nonzero *possibility*

In other words, that this is a step forward in favor of it being at least possible.

There is also a non-zero probability mount Everest could spontaneously appear right in front of you, or that a vase broken into a thousand piece could reassemble back into the original vase when you throw the pieces onto the floor. What's your point? When was the last time you saw this happening?

Arguing that something has a "non-zero" probability doesn't mean it will occur.

Zz.

 

[Greenman]

Touché, but I just wonder why so many intellectual people (people who dedicate their life to the respective field) talk about this phenomenon in such depth -

- personally for me what swayed my opinion was Takagi's book, which is why I'm dieing to know what you think of it...I assume you read it?

 

[ZapperZ]

Touché, but I just wonder why so many intellectual people (people who dedicate their life to the respective field) talk about this phenomenon in such depth -

Who?

If anyone tells you that a tennis ball can tunnel through a wall, ask them to show the experimental evidence for it! After all, the Standard Model predicts the existence of the Higgs. We don't just sit here and accept it. We go and hunt for it! This is why this is called physics, and not philosophy! The empirical component of it is necessary.

A tennis ball is a system that is made up of constituents that are not in coherence with each other! Period! Anyone who thinks that such a non-coherent system can actually tunnel together at the same time with equal probability needs to have his/her head examined, or better yet, needs to do some experimental work to have some connection to reality!

- personally for me what swayed my opinion was Takagi's book, which is why I'm dieing to know what you think of it...I assume you read it?

Nope! It would be foolish of me to review something I haven't read. Why do you hold it in such high regards?

Zz.

 

[Greenman]

It's not that they say a tennis ball can tunnel through a wall, but rather that macroscopic quantum tunneling for coherent objects is mathematically possible.

I suggest you read Takagi's book just to see what you think of it. He describes in detail how macroscopic quantum tunneling can be achieved and then provides possible systems for experimental observation of MQT.

He talks about how coherence can be maintained despite environmental factors and measurement issues.

 

[ZapperZ]

It's not that they say a tennis ball can tunnel through a wall, but rather that macroscopic quantum tunneling for coherent objects is mathematically possible.

Coherent object is a different beast. No one is arguing about that. But you are posting in a thread that are asking about a tennis ball! That is what I'm arguing.

The gymnastics that the Delft/Stony Brook experiments had to go through was to get that big, macro particle (10^11 particles) to be in coherence with each other. This is done! One has also done an interference experiments with buckyballs. Again, at very low temperature so that the thermal effects won't destroy the coherence. This is NOT the point of argument.

I suggest you read Takagi's book just to see what you think of it. He describes in detail how macroscopic quantum tunneling can be achieved and then provides possible systems for experimental observation of MQT.

He talks about how coherence can be maintained despite environmental factors and measurement issues.

But why? I mean, if he's saying that coherent object should be able to tunnel as a coherent unit, I'm not contradicting that! What exactly have I posted in this thread that is inconsistent with this?

Zz.

 

[Greenman]

I guess what I was getting at was that if the environment can be altered so as to have cohesion, then a tennis ball *could* go through a wall.

And Takagi describes how such an environment can be achieved and maintained.

Does this make sense?

 

[ZapperZ]

I guess what I was getting at was that if the environment can be altered so as to have cohesion, then a tennis ball *could* go through a wall.

And Takagi describes how such an environment can be achieved and maintained.

Does this make sense?

No.

Zz.

 

[Greenman]

Ok. I'll try to reiterate:

- Takagi describes how to create a cohesive environment.
- Quantum tunneling may occur at the macroscopic scale in a cohesive environment.

Therefore: If the tennis ball and the wall are in this cohesive environment, then quantum tunneling could occur.

Right?

 

[ZapperZ]

Read what I said as being the difference between physics and philosophy. I'm an experimentalist. You'll notice that all of my arguments are based on facts that have been verified experimentally, not just based on theoretical conjecture, or what is "possible".

Zz.

 

[Greenman]

Well, considering this is a theoretical question asking about the theoretical possibility, isn't it valid to answer with a logically-derived theoretical conjecture?

 

[ernestpworrel]

Why would anyone consider the possibility that a tennis ball could tunnel through a wall? QM doesn't even say that. All it says is that there is technically a probabilty of the ball tunneling through the wall, but it also says that there are numerous reasons the ball cannot tunnel through the wall. If you want to break the ball up into individual particles, then each particle has a good chance of tunelling through the wall but there is no real chance that the particles will coalesce into a ball with the same dimensions on the other side of the wall.

 

[ZapperZ]

Well, considering this is a theoretical question asking about the theoretical possibility, isn't it valid to answer with a logically-derived theoretical conjecture?

No, because we will then be back at Mount Everrest being theoretically possible to spontaneously appear in front of your face. After all, one can "logically derive" such a thing as well!

This is why there is such a brouhaha over the LHC and the catastrophic black hole swallowing our universe. People can't put into perspective the SCALE of possibility of things.

Zz.

 

[Greenman]

Yes, but then we go back to the fact that many very very smart people specialized in the subject have written books about the possibility. Books that are used to teach graduate level classes on Quantum Mechanics.

I haven't seen any books describing the math behind or environment needed to see Mount Everest spontaneously imploding on itself.

Surely then, this means there is a clear difference between the two?

 

[ZapperZ]

Yes, but then we go back to the fact that many very very smart people specialized in the subject have written books about the possibility. Books that are used to teach graduate level classes on Quantum Mechanics.

Where in a graduate level QM text does it tell you that a tennis ball call tunnel through a wall?

Zz.

 

[Greenman]

In Takagi's book. He describes how cohesive environments can be achieved and maintained and how macroscopic tunneling can occur in these environments.He actually uses a tennis ball and a wall as an example.

 

[ZapperZ]

In Takagi's book. He describes how cohesive environments can be achieved and maintained and how macroscopic tunneling can occur in these environments.He actually uses a tennis ball and a wall as an example.

And he has how much experimental evidence for this?

Look, I've given you examples of the Higgs, and the Delft/Stony Brook experiments. Especially in the Delft/Stony Brook experiments, they are doing nothing more than "textbook physics". Yet, these are still important experiments to show that, yes, a "macroscopic particle" CAN exhibit quantum properties. All they are doing is show how Leggett's scheme can, in fact, work! It was THE experimental verification. We didn't just sit back and applaud Leggett's cleverness at making such logical derivation out of what is essentially textbook physics!

You've jumped way past that already in your devotion to Takagi's book! This doesn't worry you at all? Forget about tunneling through a wall. Did you ever insisted to be shown this experimental evidence of a tennis ball being in such a coherent state FIRST? If there is one, please give me such a reference. Till then, I'm done with this discussion.

Zz.

 

[imiyakawa]

You can measure very accurately the position of the ball and its momentum simultaneously, and follow the trajectory of the ball every single step of the way. These are physical behavior that you cannot do with a quantum object.

According to professor Brian Greene, you can't. People just think they can because for all practical purposes a macroscopic measurement appears accurate, but it never really is.

 

[ArjenDijksman]

In Takagi's book. He describes how cohesive environments can be achieved and maintained and how macroscopic tunneling can occur in these environments.He actually uses a tennis ball and a wall as an example.

Maybe it would be better if he referred to more easily realizable experiments: http://link.aps.org/doi/10.1103/PhysRevLett.102.240401" by A.Eddi et al.

 

[ZapperZ]

According to professor Brian Greene, you can't. People just think they can because for all practical purposes a macroscopic measurement appears accurate, but it never really is.

It NEVER really is?

A "classical particle", by definition, obeys the standard classical laws. Now we can go on and argue that this is nothing more than a set of quantum laws that have undergone a gazillion decoherence, or we can argue that we are observing it using a "coarse-grained" measurements (do a search on here and you'll see that I've written several posts on this). It still does not detract from the issue that you have two separate domains here. If it is THAT easy to explain away the classical behavior, then someone should tell all those people who are working in the mesoscopic scale physics to stop wasting their time and go do something else!

Zz.

 

[boumbh]

It's just a curiosity and I'm searching for an estimation too... Like this kind of a stupid question:

I'm deliberate to apply Newtonian mechanics in a situation where it doesn't apply. On a flat surface (let's state that the Earth is flat and infinite). One train is traveling at 100km/h. An other is traveling at 100km/h on the top of the first train. The speed of the second train is therefore 200km/h. How many trains must I superpose so the top one reaches the speed of light?

This question has an answer even if it states a lot of aberrant assumptions. The answer is 10,792,529 trains (if I'm correct ). I know that to try out this experiment would require the train at the bottom to be very robust and very long (about one million km long to make it possible for all the trains to reach the speed of 100km/h), and a lot of gasoline. Also, the experiment would disprove this calculation since the principle of relativity should make a difference here.

We could also calculate the answer of this stupid question: assuming that my mother doesn't leave home, how much time must I drive my car at 100km/h, to catchup the age of my mother? (Due to time dilatation in the principle of relativity - which has been verified by experiment, so the result is expected to be a good approximation of the reality.)

I would like to know, for example, if I throw a pure graphite ball of 1/2 centimetre radius through a pure graphite wall of 1 millimetre width with a speed of 1m/s. Let's state the ambient temperature at 300K. We neglect the effect of air molecules, gravity, etc. What is the probability of the ball passing through the wall without damaging itself nor the wall? Is there a formula of the quantum principles that, outrageously applied to this case would give a result? Just to have a wrong approximation of an absurd fact, and then try to represent it.

For example : If an answer is 10^(-10^30), we can illustrate it:

If 6,000,000,000 people begins to write zeros right now with an average of 2 per second and per person, without sleeping, drinking nor eating (yes, they would die within 3 days, but), they would need 176 times the age of the universe to write down all the zeros of the number of time you need to throw a graphite ball etc. This is such an understandable illustration...

 

[pedrapgwilym]

As I see the basic nature of QT; every time you throw a tennis ball against a wall, some of it (a vanishingly small some of it) probably does 'tunnel' through the wall. You would have to keep at it for the remainder of the life of the Universe to accumulate enough of the ball on the other side of the wall to make it an observable quantity.