Collisions

[herme3]

What causes two objects to collide? How come when two objects collide, they apply a force on each other, and either stop or move in opposite directions? Why don't they just go through each other and keep moving? When programming a video game, nothing happens on its own. If you make two objects move, they won't collide unless you write a collision code and put it in the game. Without a collision code, the two objects would go through each other without causing any interference with the movement of the other object. What creates the collision code of the real world?

[Tom Mattson]

What causes two objects to collide?

 

Parts of their surfaces sharing the same spacetime coordinates.

 

How come when two objects collide' date=' they apply a force on each other, and either stop or move in opposite directions? Why don't they just go through each other and keep moving?

[/quote']

 

Same answer to both questions: the electromagnetic interaction. That's the interaction that is at play when chemical bonds are formed. If the collision is not strong enough to break those bonds, then the two objects bounce off each other. If it is strong enough, then there is damage done to one or both objects.

 

What creates the collision code of the real world?

 

1. Objects that meet at the same spacetime point collide.

2. The collision is constrained by the law of conservation of momentum.

3. If the collision is elastic, the it is further constrained by the law of conservation of kinetic energy.

[The Rebel]

In a logic world (i.e. a computer game), the results of a software code may give the same co-ordinates for a sprite, however the and/or logic will allow the result to co-exist. For example, if two seperate software equations asks for red and green pixels to be alight at 253, 450 on the display screen, the logic will simply allow red and green to be displayed.

 

In the real world matter doesn't co-exist in same place, hence a collision occurs.

[swansont]

What causes two objects to collide? How come when two objects collide, they apply a force on each other, and either stop or move in opposite directions?

 

At that level it's the electrostatic force of the orbital electrons.

[J.C.MacSwell]

What causes two objects to collide? How come when two objects collide, they apply a force on each other, and either stop or move in opposite directions? Why don't they just go through each other and keep moving? When programming a video game, nothing happens on its own. If you make two objects move, they won't collide unless you write a collision code and put it in the game. Without a collision code, the two objects would go through each other without causing any interference with the movement of the other object. What creates the collision code of the real world?

 

I would say that the electromagnetic fields of their particles that are sufficiently "in or out of phase" interact after coming "in range".

 

Good question and would find it interesting how others picture this.

 

Two thoughts come to mind:

 

1. Wave interference in a pond where the waves essentially "go through each other and keep moving". I think this is virtually elastic "collisions" of the water molecules (though they are already "in range" prior to the wave). The wave continues but the molecules return to their original positions except for minor (mostly surface) effects.

 

2. Gravity: Any possibility (probably not but why not?) that outside of my "in range" there is a small residual (not quite cancelled out) electromagnetic effect that could be the gravitational field? Any thoughts?

[swansont]

1. Objects that meet at the same spacetime point collide.

 

Not all objects. Photons don't collide, and there is quantum mechanical tunneling.

 

But this does not apply to macroscopic objects.

[J.C.MacSwell]

At that level it's the electrostatic force of the orbital electrons.

 

What about the protons. Obviously they add momentum. Are they sufficiently shielded by their electrons to not play a part in the interaction (more directly than cancelling out part of their electrons fields while transmitting their momentum also through interactions with their electrons)? I'm thinking in the case of elastic collisions.

[herme3]

Ok, what causes the electromagnetic fields and the gravity? Everyone is talking about forces and everything, yet nobody seems to know exactly what causes them. For example, science books say that gravity is an electromagnetic field, however, they never explain what creates it. They just say it is there. Talking about the properties of electrons and other subatomic particles never really answers the question. How can we explain the properties of the universe to understand the properties of matter? Is it something that we as humans just can't understand from a scientific point of view? If you really think about it, can science do anything except create more questions? I can't think of a scientific law that doesn't create more questions that can't be explained.

[J.C.MacSwell]

Ok, what causes the electromagnetic fields and the gravity? Everyone is talking about forces and everything, yet nobody seems to know exactly what causes them. For example, science books say that gravity is an electromagnetic field,[/b'] however, they never explain what creates it. They just say it is there. Talking about the properties of electrons and other subatomic particles never really answers the question. How can we explain the properties of the universe to understand the properties of matter? Is it something that we as humans just can't understand from a scientific point of view? If you really think about it, can science do anything except create more questions? I can't think of a scientific law that doesn't create more questions that can't be explained.

 

Science books don't say that! I know my post raises that as a question but it's not even a half baked idea. Sorry if I didn't make that clear. I try to make it clear when I'm off the beaten path. In fact I suspect it has been ruled out (given certain assumptions), but I've never seen it before.

 

As to the rest of your post no one really knows in non-mathematical terms. I find it interesting how people "picture" subatomic levels.

[herme3]

Oops, I meant to say magnetic field, not electromagnetic field.

[J.C.MacSwell]

Oops, I meant to say magnetic field, not electromagnetic field.

 

Gravitational field?

[herme3]

No, my Physics book said that gravity is like a magnetic field. That's all it said. Then it went on to talk about some mathematical formulas. It never said what creates gravity, or what creates any other forces.

[J.C.MacSwell]

No, my Physics book said that gravity is like[/b'] a magnetic field. That's all it said. Then it went on to talk about some mathematical formulas. It never said what creates gravity, or what creates any other forces.

 

Ahh! As in inverse distance squared.

 

Quantum field theory has some answers, and like you said... more questions.

[swansont]

What about the protons. Obviously they add momentum. Are they sufficiently shielded by their electrons to not play a part in the interaction (more directly than cancelling out part of their electrons fields while transmitting their momentum also through interactions with their electrons)? I'm thinking in the case of elastic collisions.

 

Tthe protons don't really play a direct role - they are effectively screened by the electrons, as you say. Any force that are exerted on the electrons get transferred to the protons by the electrostatic force. The whole atom/molecule is affected.

[swansont]

Ok, what causes the electromagnetic fields and the gravity? Everyone is talking about forces and everything, yet nobody seems to know exactly what causes them. For example, science books say that gravity is an electromagnetic field, however, they never explain what creates it. They just say it is there. Talking about the properties of electrons and other subatomic particles never really answers the question. How can we explain the properties of the universe to understand the properties of matter? Is it something that we as humans just can't understand from a scientific point of view? If you really think about it, can science do anything except create more questions? I can't think of a scientific law that doesn't create more questions that can't be explained.

 

Gravity is caused by mass and energy warping space. Electric fields are cuased by charged particles. Magnetic fields are caused by charged particles in motion.

 

We know what causes them. Science textbooks are pretty good at explaining this. What we don't know, at a fundamental level, is why these things are so. Science is the investigation into how nature behaves, but not necessarily into why it behaves that way.

[J.C.MacSwell]

Tthe protons don't really play a direct role - they are effectively screened by the electrons, as you say. Any force that are exerted on the electrons get transferred to the protons by the electrostatic force. The whole atom/molecule is affected.

 

Not sure how this is related but if you "shake" a proton it should send EM similarly to "shaking" an electron. In what way will that "signal" be different? How will an electron know to be attracted and not repelled.

 

I picture it as a spin "combination" but I have no real idea of the "current" (no pun intended) view.

 

I think I'm somewhat mixing up EM with "pure" E or M signals, but my "picture" is fuzzy.

[swansont]

Not sure how this is related but if you "shake" a proton it should send EM similarly to "shaking" an electron. In what way will that "signal" be different? How will an electron know to be attracted and not repelled.

 

If it's a free proton, yes. But since it's three orders of magnitude more massive than an electron, you won't get the same spectrum out of it for the same force.

 

I'm not sure what you mean by knowing whether to be attracted or repelled.

[J.C.MacSwell]

If it's a free proton' date=' yes. But since it's three orders of magnitude more massive than an electron, you won't get the same spectrum out of it for the same force.

 

I'm not sure what you mean by knowing whether to be attracted or repelled.[/quote']

 

I realize that but you would get the same spectrum for the same "route"?

 

Any measureable differences in the resulting photons? (polarization?)

 

As for attraction/repulsion what mediates the electrostatic force? If it is photons how are they "sent" without accelerations of an electron or free proton? So how would an electron (say) know to be repelled or attracted?

[jdurg]

In my P-Chem class we went over how there is a finite probability that a solid object can pass right through another solid object. So there is a chance that I can run full speed right into a wall and pass right through it. However, that probability is something like 1 in 1x10^(Some insanely large number). For all effects and purposes, it's zero. But mathematically it isn't completely zero.

[J.C.MacSwell]

In my P-Chem class we went over how there is a finite probability that a solid object can pass right through another solid object. So there is a chance that I can run full speed right into a wall and pass right through it. However, that probability is something like 1 in 1x10^(Some insanely large number). For all effects and purposes, it's zero. But mathematically it isn't completely zero.

 

That's correct. One of the infinite monkeys just wrote a paper on that!

[jdurg]

I guess for one atom the probability isn't all that bleak, but when you start mathematically combining the probability for the number of atoms inside a human being, then the probability becomes really bleak.

[swansont]

I realize that but you would get the same spectrum for the same "route"?

 

Any measureable differences in the resulting photons? (polarization?)

 

As for attraction/repulsion what mediates the electrostatic force? If it is photons how are they "sent" without accelerations of an electron or free proton? So how would an electron (say) know to be repelled or attracted?

 

Yes' date=' for the same acceleration, you should get the same radiation for protons and electrons, as far as I know. I don't know if there would be a polarization difference.

 

The photons are virtual so there is no energy or momentum worries unless there is an interaction. The attraction and repulsion is caried in the interaction of the virtual particles.

[J.C.MacSwell]

Yes' date=' for the same acceleration, you should get the same radiation for protons and electrons, as far as I know. I don't know if there would be a polarization difference.

 

The photons are virtual so there is no energy or momentum worries unless there is an interaction. The attraction and repulsion is caried in the interaction of the virtual particles.

 

Thanks, I bookmarked the link.

[Tom Mattson]

Not all objects. Photons don't collide' date='

[/quote']

 

There are, in fact, photon-photon collisions. They take place through intermediary virtual particle-antiparticle creation. There's a nice Feynman diagram of the process in the Introduction to Jackson's Classical Electrodynamics.

 

But that is neither here nor there, because all QED processes fail to meet one of my stated criteria for collisions: two objects must share the same spacetime coordinates. I was hoping it would be clear that this is only for classical dynamics.

 

and there is quantum mechanical tunneling.

 

I wouldn't call a quantum mechanical potential an "object", in the sense that I have been using the term. My usage of it refers to material bodies.

 

But this does not apply to macroscopic objects.

 

Right-O.

[Tom Mattson]

I would say that the electromagnetic fields of their particles that are sufficiently "in or out of phase" interact after coming "in range".

 

EM fields are only said to have a phase when they are EM waves. But we aren't talking waves here.

 

1. Wave interference in a pond where the waves essentially "go through each other and keep moving". I think this is virtually elastic "collisions" of the water molecules (though they are already "in range" prior to the wave). The wave continues but the molecules return to their original positions except for minor (mostly surface) effects.

 

There are no collisions between water molecules in a water wave (excluding breaking waves' date=' of course). Each element of fluid moves up and down [i']only[/i].

 

2. Gravity: Any possibility (probably not but why not?) that outside of my "in range" there is a small residual (not quite cancelled out) electromagnetic effect that could be the gravitational field? Any thoughts?

 

Don't understand this part.