# Hand through table?

1. May 3, 2005

### Mozart

I was watching a show called Daily Planet a while back when some author of a Science book said something like, "There is a probability that my hand will go right through this table."

I started thinking about what he said, and I rememberd hearing one of my Science teachers 2 years ago saying atoms are 99% empty (I don't know if this is true or not I may have rememberd wrong). I was also thinking about how matter isn't continuous and it contains gaps. So what is in my head is the following. Imagine each period is a single atom

Finger----> . . . . . . . . . . . . .
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . .

Table ------> . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . .
. . . . . . . .. . . . ... . . . . . . .

So by looking at that very awkward depiction of atoms it seems that there is a chance that your finger will go through the table. Maybe it will go through until it becomes blocked by other atoms. So is this a proper way to think about the chances of matter going right through matter? Oh, and what about the electrons? Is it because they are bosons that they just pass right through each other without disturbing its orbital path?

2. May 4, 2005

### nmondal

There is a probability and that too is 100% is that, the Guy who said it is MAAD.

:yuck:

People, without appropriate context should not talk like that.
In the mean time the picture you drew is a waste, as that shifting never happens in the solids. Any kind of solids.

Ok...
Here is the case...it CAN NEVER HAPEN.
No SOLID exists in the world for which this can happen, it happens for ice with sharp edged object into it.

Why?
In case of ice, that answer does not require a real innovation.
Why the thing mentioned above never happen?

There exist something called an electron, and something called bonding.
:surprised
So by the property of solids, we just do not have to worrry about the scenario that you mentioned.
If the other thing happens, then do not call the thing a solid.
A table is always solid.

3. May 4, 2005

### inha

yeah that was more likely just an pop-sci analogy for tunneling. maybe mindboggling but also horribly inaccurate.

4. May 5, 2005

### Gokul43201

Staff Emeritus
No, it's not. You can not think of quantum mechanical phenomena classically, especially if one doesn't know the QM involved.

No. Electrons are NOT bosons. They are Fermions and they certainly repel each other through the Coulomb interaction.

5. May 5, 2005

### hexhunter

this might be in reference to branes, in that documentary on the string theory the guy starts talking about how all posibilities have a chances of being the outcome, i'll ahve to watch that bit again... i think it was around the bit where he starts with branes and the 11 dimensions...

6. May 5, 2005

### PIT2

I think thats in the video called 'the quantum cafe' on this site:

http://www.pbs.org/wgbh/nova/elegant/program.html

7. May 5, 2005

### hexhunter

yup, thats it...

8. May 6, 2005

### Spastik_Relativity

mozart,
ive got to say that that is ludacris. the strong nuclear force will repel you if your hand was to have any penetration aanyway

9. May 6, 2005

### LURCH

I am sure that the statement was indeed a reference to tunneling, which is a verified phenomenon, a result of Uncertainty. The statement is correct as stated, "there is a probability...". However, one must understand that in this context the use of the word "probability" merely means that the chances are not mathematically zero. The only questionable turn he uses his the phrase "pass through", since tunneling would be more accurately described as his hand getting from one side of the table to the other without passing through it.

After all, the man's hand is a material object, and matter is made of Quantum articles. The location of any one of these particles as a degree of uncertainty to it. Included within the "possible" locations of each of these particles is a location on the far side of the table. However, the distance from the top of the table to the underside is so great (in Quantum terms) that the probability of anyone particle occupying this location is extremely low. The probability of all of the particles in the man's hand existing on the far side of the table can be found by taking the odds against one particle making such a jump, and multiplying it by the number of Quantum particles in the man's hand. The result is still >0, but a probability so very low that, if the man were to strike the table with his hand five times per second since the beginning of the universe, he would still just be hitting the table and stopping every time.

But, given an infinite number of tries, there would be some occasions on which the hand is found on the far side table, giving the appearance that it had "passed through".

10. May 6, 2005

### Hans de Vries

Since the laws of Quantum mechanics are not infinitely mathematical perfect
one can savely say that the chance is absolutely zero, zero, zero.

Not zero is for instance is the chance that one acquires a genetic disorder,
spontanously grows wings, and then becomes the first man or woman to fly
around the world using them.

Luckely, popular Bio.science programs do not seem to need stuf like this.
For the time being at least...

Regards, Hans

11. May 6, 2005

### learningphysics

If Quantum mechanics were "perfectly true", then would there be a non-zero probability?

12. May 6, 2005

### Hans de Vries

The QM effect in general is about how particles can temporary (for a short
time) have some extra energy to tunnel through a barrier. The longer the
time needed or the higher the energy required the less likely it becomes.

1) A single atom in your hand would need to acquire a large amount of extra
energy for a very long time: very unlikely but maybe not zero.

2) Now all the atoms in your must acquire a huge energy all at the same time:
extremely unlikely. The general result would be that your hand explodes.

3) Now the real miracle must happen: Your hand should not explode but
by sheer chance all atoms should bang in perfect concert through the
table and appear at the other side at exactly identical relative positions.

4) Next miracle is that all the atoms lose the extra energy in perfect
concert to stop as if nothing has happened. Yet another required miracle
is that the table remains unharmed by all of this.

The recipe for mindless extrapolation:

Electron tunnels through barrier => Hand tunnels through barrier
just replace sound "electron" by sound "hand" and make sure not
to think any further.

Regards, Hans.

13. May 6, 2005

### Pengwuino

One of my professors said this was possible though. He's example was his hand passing through a wall and he said that its possible except that you'd ahve to wait a few of the universes current lifespans before it would ever happen but he made it clear that there is a mathematical possibility.

14. May 6, 2005

### ohwilleke

There is a similar hypothetical that involves nothing but classical gas kinetics.

There is some possibility, exceedingly remote to the point of being so unlikely that it will probably never happen, that the molecules of oxygen in your bedroom could all end up in the part of the room where your mouth and nose are not, for some period of time. If that period of time was long enough, you could suffocate and die.

But, the law of averages applies viciously with a large population of gas molecules. There are 6*10^23 molecules of oxygen in 16 grams of the stuff. Air is about 21% oxygen at sea level (the nitrogen and nobel gases that make up most of the rest is essentially inert for breathing purposes). Air weights about 1 gram per liter. Nitrogen is 7/8th the weight of oxygen, so oxygen is about 23% of air by weight. A typical bedroom might have 10,000 liters of volume. This means that there are about 1.4*10^27 oxygen molecules in a typical bedroom.

Normally, 1.4*10^22 oxygen molecules are going to be in the general vincinity of the 1 liter of your bedroom containing your mouth and nose. The odds of most of those oxygen molecules going to some other part of the room for any extended period of time are astronomical.

To apply the law of large numbers rather crudely, and say that each oxygen molecule has a 1/10,000 chance of being in that liter of air and that you apply this 1.4*10^27 times, the number of molecules of air in that liter is going to hover very close to the mean expected number of molecules.

Also, 1/10,000 chance is really something that ought to be applied at a frequently roughly comparable to the time it takes a molecule of air to travel a decimeter (since a liter is a cubic decimeter). Air molecules at room temperature move at 500 m/s on average. http://www.newton.dep.anl.gov/askasci/chem03/chem03448.htm

Thus, you really need to recalculate the the number of air molecules around your head about 5000 times per second.

Since you would have to be deprived of oxygen for perhaps 2 seconds to even notice the effect, this means that you'd basically have to beat the law of large numbers 10,000 times to have even a noticeable effect, and in each case this means that one has to come from applying the 1/10,000 determination about 1.4*10^27 times and come out far from the mean. And, that is just to notice it.

To get a real scare and be without oxygen for say 2 minutes, this deviation has to take place 600,000 times. In other words, an event with a 1/10,000 chance of happening has to happen at a frequency significantly different from the average frequency when repeated an 8.4*10^32 virtually independent occassions. The standard deviation is roughly 10^14 and the mean is roughly 10^22. Thus, 95% of the time (i.e. roughly 2 standard deviations), the number of oxygen molecules in the 1 liter of your bedroom that contains your head will be within 2*10^-6 percent of normal. At 50% reduction in the number of air molecules around your head for two minutes is at z=10^13 or so on the normal distribution curve. Converting that z score into an ordinary probabilty is off the chart of most computer programs designed to do that. A probability of this event happening every two minutes of once or twice in 10^15 would be once in the time period from the Big Bang to now. The probability of something with this z score happening is less than .01^z or on a comparable order of magnitude. In short it is so improbable that it will never happen.

Anyway, the hand through the table quantum mechanics example requires events with probabilities on an order of magnitude less probable. In short, these are events are so rare that they will never happen.

Last edited: May 6, 2005
15. May 6, 2005

### PIT2

Someone should test this in an experiment :rofl:

16. May 6, 2005

### learningphysics

I believe there is a vast difference between saying that something is impossible according to a theory, and something is exceedingly improbable. Practically it may make no difference. But conceptually there is a great difference.

17. May 6, 2005

### ZapperZ

Staff Emeritus
Can you elaborate, or give an example, on how such a knowledge can make a "great" conceptual difference?

Zz.

18. May 6, 2005

### Pengwuino

IMHO, impossible vs. insanely improbable means a physical object can be modeled in 2 different ways. With a hugely improbable situation like this, we might assume that atoms are not full solid components. If it were absolutely impossible, we would have to model atoms in a way that it was physically impossible for something to pass through which would present a different model then the previous one.

19. May 6, 2005

### learningphysics

If it is improbable (if the probability is nonzero), then given an infinite amount of chances the event will happen. However if it is impossible, the event will never happen. So there is a conceptual difference. With one scenario the event happens... with the other it doesn't (not in the real world, but within the conceptual framework)

It would be like saying that tunneling is exceedingly improbable according to classical mechanics as opposed to saying that it is impossible according to classical mechanics.

Let me ask a different question. If a hand were to go through a table, then is QM necessarily violated?

20. May 6, 2005

### ZapperZ

Staff Emeritus
But you stated that there is a great conceptual difference. These are not "conceptual", are they? They are more..... er.... "technical", and honestly, as someone who has done tunneling spectrum AND had to deal with modelling of band structure, I don't see any great technical difference between "infinite barrier" and "very, very, very, large barrier", the same way I don't see any technical difference between "very, very small gravitational field from alpha centauri" with "no gravity from alpha centauri".

Zz.