In an experiment a couple of plates separated by 10^-6 metres yielded a casimir force of 10^-7 Newtons / m^2 So, 10^ - 7 = constant x 1 square metre / (10^ -6 ) ^ 4 constant = 10 ^ -31. If a quark is a sphere of partial electric charges it has a radius of 10^ -18 metres at most because particle accelerators have not yet found structure at their current resolving power. Assuming the two halves of the sphere are like casimir plates, they have an area of 10^-36 square metres and a radius of 10^-18 metres. This yields a casimir force of 10 ^ 5 Newtons pushing the spheres together. This force is generated by vaccum particles. The hydrogen atom consists of 3 quarks orbited by one electron. We will represent the quarks by one large spherical quark with a radius of around 10^-18 metres. The electron orbits at 10^ - 10 metres. If vacuum particles push the electron towards the quarks and keep it in orbit around them then they must generate a force given by k q1 q2 / r ^ 2 which is 10 ^ - 8 Newtons. This must be the case at every point on the electron’s orbit. So if the electron is a sphere like a quark how big is this sphere. The casimir force on the quarks is 10 ^ 5 Newtons . This can be generated by 10 ^ 13 vacuum particles x 10 ^ - 8 Newtons – at least one particle for each position on the electron’s orbit. This means that an electron has a maximum radius of 10 ^ - 10 / 10 ^ 13 m that is to say 10 ^ -23 metres. The electron is at least one hundred thousand times smaller than the quarks! It will take particle accelerators some time before they can find the structure of the electron.