Question: Quantum electrodynamics is confusing me. How can there be virtual photons to make positive and negative attract? How can these photons exist if they're not technically there?

Alessandro Guazzi answered on 13 Mar 2013:

You’re really probing at the heart of physics and the way we understand the world! Quantum electrodynamics is one of the last things they teach you in Physics at university, no wonder you’re a little confused! 😉

The thing is, the photons are called virtual because they only exist for a very limited period of time. But that’s beyond the point – the key thing I think confuses people is that, because you learn in Physics that stuff is made a certain way, people think that stuff like electrons, photons, or virtual photons actually exist. In reality, we don’t know if they do or they do not, they’re just useful concepts to help explain the world around us. Your example of the positive and negative attracting is very good at showing that:

To begin with, we noticed that we could charge materials so that some would become more positive and others more negative, and we noticed that opposite charges would attract. We measured the force of the attraction (which we called the Coulomb force) and said that each charge has a field around it, and that the attraction between opposite charges is due to the interaction of the fields. These concepts, which were those of classical physics, were useful, because they allowed us to predict stuff, but they weren’t necessarily true!

Now we’re trying to explain things in terms of quantum physics, and according to quantum physics there are four fundamental forces, and electromagnetism is one of them. Each of the forces is due to an exchange of a particular type of particles. For electromagnetism, photons are the exchange particles. So in quantum physics we like to explain everything in terms of charged particles such as electrons or protons exchanging these photons between them and feeling a force as a result. But again, this is only a nice, useful concept that helps us make predictions and understand what’s going on better!!! As we measure stuff that’s getting smaller and smaller, our experience as humans and on a large scale can no longer help us explain what is going on, and we cannot ever hope to understand or “see” it – we can only try to explain it using concepts such as “fields” or “virtual photons”.

I hope that answered that question and didn’t confuse you even more! If you want to read up on the quantum physics theories (quantum electrodynamics is just the quantum theory of electromagnetism) then this site is very good:

Go here for QED:
http://hyperphysics.phy-astr.gsu.edu/hbase/forces/qed.html

And here it has an overview of all the theories of physics (QED is in the fundamental forces branch of the quantum physics):
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html