Fermilab

Hello,
I am fascinated by the universe of physics, and I have a few questions. Actually, I was wondering about photons. I have come to understand that photons are the force carrying particles for the electromagnetic force. I also understand that they have no mass and can therefore travel at the speed of light.

What I was wondering was this: When two electrons come near, why are real photons said to be emitted, but virtual photons are said to be the actual carriers of the electromagnetic force? What is the difference between the two, virtual and real?

Also, I want to pose another question. When static electricity is created, are the electrons stripped away from the compound being charged? If so, wouldn't this change molecular, metallic, or ionic bonds and cause a new compound entirely to be created? Basically, I am wondering how and why objects gain a charge. Thanks a lot.

Hi Ben,

great, we are on the same wavelength when you say you are "fascinated by the universe of physics". That is a great start.

You asked:

When two electrons come near,why are real photons said to be emitted, but virtual photons are said to be the actual carriers of the electromagnetic force? What is the difference between the two, virtual and real?

I am not sure what exactly you mean when you say "real photons said to be emitted". There are many processes where charged particles are involved and real, detectable photons are emitted or absorbed. I think the closest to your question might be the fact, that any charged particle which undergoes acceleration EMITS REAL PHOTONS!!

This fact comes as a direct consequence of Einstein special relativity. In fact, this is precisely the mechanism, how the electromagnetic signals of TV broadcasting, or cell phones, or radio broadcasting are created. They take a bunch of electrons, they have them moving periodically up and down in the emitter antenna ( note, when electrons move periodically up and down, they have a non-zero acceleration) and therefore they shine photons ( electromagnetic waves) which are the waves you receive at home. To read more about this, you can check out our web sites dedicated to light on:
http://www.fnal.gov/pub/light/

In your particular case, I think the trick with the emitted real photons is the following: when two charged objects are near by, they act with a force on each of other, therefore they undergo acceleration, therefore they shine out real, detectable photons. So much about real photons.

As far as the VIRTUAL photons are concerned, I would not like to repeat myself here. I rather give you a link to answers I/we gave in the recent past to a similar question as yours.

So, would you please first check out the following two answers by selecting:

1) Antimatter and Virtual Photons or
2) Virtual Photon Question

If you still have questions, please ask.

Your next question was:

When static electricity is created, are the electrons stripped away from the compound being charged? If so, wouldn't this change molecular, metallic, or ionic bonds and cause a new compound entirely to be created? Basically, I am wondering how and why objects gain a charge.

Yes, when a positive static electricity is created, it really happens that electrons are taken away from atoms/objects. Then of course, this process changes the physical properties of atoms or the material the electrons were taken from. Sometimes it makes a drastic change ( if you "shave" a hydrogen atom, you got a proton), sometimes it is hardly noticeable ( if you charge a hair comb, when you comb your hair, you do not see any difference at first. The comb is still a comb, even if you took some of its electrons from it!)

So, my point is, that YES, by charging objects by taking or adding electrons you change their properties. However, it depends on the particular situation how drastic influence this stealing or adding of electrons will cause.

Wait a minute, it just came across my mind. There is another way how to change the charge of objects. By taking or adding protons to neutral atoms!!! If this is the case, then YES, this is a VERY VERY DRASTIC CHANGE!!!

Why?

The number of protons in the nucleus decides what kind of matter one has. For example, if you have an atom with 7 protons in its nucleus, it is called nitrogen. If you take this atom, and you take an electron away from it, you still have a nitrogen atom, but is positively charged. However, if you take a PROTON away, it will be a NEGATIVELY charged CARBON atom ( which has 6 protons ). So, you see that by changing the charge of an atom by taking or adding protons has a huge impact on the atomic structure. It needs to be added that to change the charge of objects by taking or adding electrons is very very easy. To change the charge of atoms by taking or adding protons is extremely difficult, because protons are tight down very strongly in the nucleus.

There are many ways objects can be charged. Mechanically ( comb will be charged when you comb your hair), electromagnetically by running electric current to objects ( current is a bunch of electrons moving in a wire), by shooting particles on matter, by creating very strong electric fields ( like clouds build up charge by moving in the air, and then they discharge by a lightning to the Earth) ... .

I hope I answered your questions. If not, please let us know.

Bye, Arnold Pompos
Graduate Student at Fermilab

Back to Questions About Physics Main Page