Since atoms dont touch?

Question

If two objcects never actually touch, what are we feeling when we feel different objcects? I understand the concept of the atoms repelling other atoms, but if all atoms just repel other atoms, why does plastic feel like plastic and wood feel like wood etc. Also whats happening when fingerprints are being left on an objcet? are the atoms of the oil kind of floating above the object?

Answer 1

It all depends on your definition of touch.

Within a piece of metallic iron the nuclei of the various atoms don't touch. Each nuclei is surrounded by an electron cloud and the majority of the electrons around each atom are in an energy level that ensures they are not going to move away from that nucleus. The outermost electrons are shared by the atoms in a conduction band. This is true in all metals which results in them being conductors of electricity. In metals the atoms are packed more tightly together than in other materials yet they are still mostly empty space. The interaction between the electrons and the nuclei, between different nuclei and so on are mostly electrostatic forces.

Now consider two pieces of scotch tape. If you sick a piece of scotch tape onto another piece and then pull them apart there is a resistance to them coming apart. The forces involved are electro static forces. Pulling the two pieces apart will result in one getting a positive charge and the other will get a negative charge. If you hang each piece from a pencil and bring them close together you will see they will attract each other.

If one uses four pieces of tape one can demonstrate electrostatic repulsion. Stick two pieces of tape to a table (a few inches apart and never touching). Place the third piece of tape on the 1st and the 4th on the second. Rip the top pieces off. Hang each from a pencil. As these pieces are brought together one should see they repel each other (they will have the same charge – the tape still on the table will have the opposite charge.

To do the experiment the two pieces of tape must stick together. Electrons get pulled off one piece and attached to the other. From the zoomed in perspective at the atomic level the pieces don’t touch. Even the atoms making up one piece of tape don’t actually touch. From the zoomed out macroscopic point of view the bits of tape not only touched but electrons transferred from one to the other without jumping through the air. It is possible to stick the two pieces of tape together to the point that no air molecules are between them. From a macroscopic perspective this means they are touching.

Getting back to your question the sweat in the finger print adheres to the surface it is on. It certainly is not going to move with air currents and it could not be said to be floating. At the macroscopic level the sweat of the finger print is attached to the surface and they would be understood to be in contact. Also keep in mind that a surface may be quite smooth at a macroscopic level but it is most likely going to be very irregular at the atomic level. The surface will have ridges and valleys many atoms deep so while the atoms may not actually touch they will be somewhat interlocking. This would lead to the interpretation that they are in contact at a macroscopic scale. Keep in mind at the atomic scale observation becomes at best imprecise because of the Uncertainty Principle. http://en.wikipedia.org/wiki/Uncertainty_principle#History_and_interpretations
Also keep in mind that the force between two charges is inversely proportional to the distance between them. At tiny distances the forces become big.
http://en.wikipedia.org/wiki/Coulomb's_law#Scalar_form
Materials in “contact” will be irregular at the atomic level but there can be bonds formed at the points of contact between two materials.

Objects feel as they do to the touch of human finger tips due to the macroscopic texture. We describe the feel to be hard, soft, rough, smooth, slippery or binding. The nerve endings that pick up the sensation are not exposed on the surface of the fingertips but protected in the living skin cells beneath a layer of dead cells. The nerve ending respond to tugs, vibration, temperature and pressure from the overlaying skin so the sensation is only indirectly related to interface between the skin surface and the object “touched”.
http://en.wikipedia.org/wiki/Fingerprint

http://library.thinkquest.org/3750/touch/touch.html

Answer 2

You're right. On the atomic scale, when you touch a table, or a bowling ball, or your spouse, etc., you are not actually touching them!

Instead, you are feeling the Coulombic repulsion of between the atoms on your finger and the atoms in your coffee cup. When you take a sip fo the coffee, the atoms of coffee never actually touch your digestive system either, they simply transfer heat, and thus energy.

The world of touch senses is actually a big illusion. When you feel the soft cottonball you are actually responding to a highly disordered Coulombic repulsion array. When you feel the sharp tip of a knife, you are feeling the highly localised Coloumbic repulsion array. Plastic feels like plastic and wood feels like wood because we have trained ouselves to interpret that particular array of Coulombic repulsion as plastic and wood.

As for the fingerprint, yes the oil is hovering above the object, in balance from the Coulombic repulsion pushing it off, and the dispersion forces that are pulling it in. But again, the oil in the fingerprint never actually touches the object. But then again, nor do any of the atoms in the object -- nor in our bodies -- ever actually touch each other either. They are players in the eternal balance between attraction and repulsion.

This whole concept has always blown me away. When I eat a burrito, I'm not actually eating it, so much as I am letting my body break apart its molecular bonds and absorb its energy.

Answer 3

What you are feeling when you touch a object is a manifestation of the electrostatic forces between the atoms in that object and the ones in your hand. The Resistance you encounter when trying push your hand through a wall or any rigid object is a result of the inter/intra molecular forces within the rigid object.

When we say atoms don't actually touch its because most of an atom is extra space(electron orbitals).

Answer 4

How life began is a complex question with many potential answers and more information is gathered every day. However, the questions of how life began have no bearing on the fact that evolution has occurred/is occurring. The fact that the primordial Earth is completely obliterated may forever prevent us from discovering how life on Earth specifically originated. It does not change the fact that evolution has occurred and can be observed to be occurring wherever there are living organisms. Anyone insisting that evolution is invalid without a valid theory of abiogenesis is simply lying.

Answer 5

Hi. Touch on the atomic level is much different than touch on the human level. We sense texture by nerve conduction. Atoms are responding to different forces. (By the way, they touch in a neutron star!)