No two objects can touch?

[starfire09]

Hey! I've been lurking around these boards for a long time, just reading stuff, but haven't posted anything since I know so little compared to all of you guys @_@. So for my first post, I thought I'd ask a question that had been bugging me for a while. So one of my high school friends is in an AP Physics class, and he was describing to me a lecture that his teacher gave about how no two solid objects can actually come in contact with each other because of the atomic particles' repulsion. Now, I'm a chemistry guy, so I can kind of appreciate what he was talking about, but am unsure to the forces involved. First of all, is it true what he said, that no two objects can touch one another? And if it is, what causes this? Is it that once the distance gets so small, the intermolecular forces are so intense that they repel extremely "hard?" If that's the case, what is our perception of "touch?" Say I touch my finger to my face, is it the strong forces between positive nucleus to positive nucleus that makes me "feel" my cheek flexing in? Then what happens when somebody is, say, shot with a gun? Does the bullet just repel the electrons in somebody's chest so fast that it causes tearing, thus a hole?

 

Ugh, all these questions I have makes me so glad that I chose to pursue chemistry as a major instead of theoretical physics. (-.-')

[max.yevs]

i suppose he meant it like between atoms, and their nuclei,

since nuclei of atoms are positive they repel each other

 

until they are close enough that gravitaional forces take effect;

then the nuclei might fuse, as in nuclear fusion

[Norman Albers]

Nature gives us levels of organization. Rock, paper, scissors. We experience structure mostly on the molecular level, and that is so complex. . .

[iPeppers]

Hey! I've been lurking around these boards for a long time, just reading stuff, but haven't posted anything since I know so little compared to all of you guys @_@. So for my first post, I thought I'd ask a question that had been bugging me for a while. So one of my high school friends is in an AP Physics class, and he was describing to me a lecture that his teacher gave about how no two solid objects can actually come in contact with each other because of the atomic particles' repulsion. Now, I'm a chemistry guy, so I can kind of appreciate what he was talking about, but am unsure to the forces involved. First of all, is it true what he said, that no two objects can touch one another? And if it is, what causes this? Is it that once the distance gets so small, the intermolecular forces are so intense that they repel extremely "hard?" If that's the case, what is our perception of "touch?" Say I touch my finger to my face, is it the strong forces between positive nucleus to positive nucleus that makes me "feel" my cheek flexing in? Then what happens when somebody is, say, shot with a gun? Does the bullet just repel the electrons in somebody's chest so fast that it causes tearing, thus a hole?

 

Ugh, all these questions I have makes me so glad that I chose to pursue chemistry as a major instead of theoretical physics. (-.-')

 

This is true. When I press my hand against a wall, the only thing stopping my hand going right through it is the atoms and molecules of the wall repulsing the atoms and molecules in my hand, and vice versa.

 

You would think that since atoms are made up of mostly empty space (and thus all matter is as well), that I should be able to walk through a wall. But the electrons and protons that make up the atoms are charged and will repel each other. So technically the basic building blocks of matter in my hand don't necessarily physically touch the matter in the wall, but what I feel is the repulsion between them.

 

Of course atoms are always moving and we are constantly swapping atoms and their electrons with everything we touch and even the air around us. The earth is just one big moving soup of matter.

[cameron marical]

sweet. so if you say ionize something to a great degree, say a wall, so there is little or no electrons around that wall, could we essentially walk through it? would it just dissentegrate?

[Norman Albers]

Where it gets hairy is when you look at small entities. There, things do go through walls. Quantum tunneling is the term for it.

[iPeppers]

sweet. so if you say ionize something to a great degree, say a wall, so there is little or no electrons around that wall, could we essentially walk through it? would it just dissentegrate?

 

Well if you took away all the electrons in a wall, it would quickly grab more from the air around, or from you trying to walk through it. And also if it had no electrons, then it's molecules would break apart and it would probably be more like a gas or plasma if it was contained.

[cameron marical]

so why dont photons just keep going through anything? they have no mass, so they arent changed or directed by electrons or protons, are they?

[Norman Albers]

They sure are. Unless they are ripping high energy then maybe not. Then again, ranges of absorbing and transmitting are all over the map and this is a good study. Like, the radio device can still receive signals from a tower even after going through your head, if that's how you're facing, right?

[max.yevs]

sweet. so if you say ionize something to a great degree, say a wall, so there is little or no electrons around that wall, could we essentially walk through it? would it just dissentegrate?

 

you know a way to strip off all the electrons from a compound, right?

 

heat it into a plasma ....

 

with enough energy, electrons dont want to stay tied so close to their nuclei, they'd much rather fly around randomly!

[Norman Albers]

Dang, sounded like a possibility for a joke. We'll work on that. You are describing the toasting of molecular forms.

[swansont]

i suppose he meant it like between atoms, and their nuclei,

since nuclei of atoms are positive they repel each other

 

until they are close enough that gravitaional forces take effect;

then the nuclei might fuse, as in nuclear fusion

 

Gravity isn't a noticeable effect in fusion, The nuclear force is much, much, much, much, much, much, much, much, much, much, much, much, much larger.

 

——

 

Even though atoms are neutral, atomic repulsion occurs because when they get close enough, the screening of the charges isn't as strong. There's no net charge, but you see effects from charge distributions (e.g. dipoles), and these induce charge distributions in nearby atoms and molecules. Dipole forces, for instance, drop off as 1/r^3, and induced dipoles drop off as 1/r^6, and there are even higher-order effects, so these forces aren't noticeable until the atoms/molecules get really close to each other.

[Norman Albers]

Dipole forces, for instance, drop off as 1/r^3, and induced dipoles drop off as 1/r^6, and there are even higher-order effects, so these forces aren't noticeable until the atoms/molecules get really close to each other.

 

Thanks for that; I have wondered about figuring Casimir effect as mutual dipole induction.

[swansont]

Thanks for that; I have wondered about figuring Casimir effect as mutual dipole induction.

 

That's related to what it is. You have a dipole, which induces a mirror-image dipole in the conducting surface. What I've wondered is, if you could get the original dipole to oscillate, but have the mirror be pi out of phase (because of the time lag from the distance to the conductor), could you turn this into a repulsive force? Then do the experiment vertically, so the repulsive force balances gravity, and the atom sits just above the surface.

[Norman Albers]

I figure the polarization as a fluctuation field... hmmm.

[iNow]

HI thought I'd ask a question that had been bugging me for a while.

 

I always liked the way this IMAX presentation puts it all together. Good learning aid from the very large to the very small:

 

http://video.google.com/videoplay?docid=5757507304603419799&ei=N6PLSdC6C5KWrALF8pX1Bw&q=cosmic+voyage

[YT2095]

so why dont photons just keep going through anything? they have no mass, so they arent changed or directed by electrons or protons, are they?

 

they do, x-ray pictures exploit this, or the wi-fi in your computer, or mobile phone etc....

[Kaeroll]

In response to the OP... I've always felt this is something of a fallacy. The sensation of touch is a product of the electron repulsion described- since when does 'touching' an object require nuclear fusion?

[insane_alien]

its more of trying to apply a classical concept at the quantum level. of course it fails because you are trying to mix and match from two different regimes.

[Norman Albers]

Responses are entirely distinct in different energy regimes.

[Patrick Henry]

they do, x-ray pictures exploit this, or the wi-fi in your computer, or mobile phone etc....

 

But eventually they will be refracted, correct?