# What made Ising propose the nearest-neighbor Ising model?

I get that the spins can interact not just the nearest neighbour in the general sense. But why in Ising's paper when he solves the linear chain model, he consider spins can only interact with nearest neighbour spins? In his paper, he got mention the reasons, but I don't quite understand as I don't understand German. Why did he say that the forces exert by the spins fade with distance?

You can think of each little spin as being a small little magnetic dipole. The magnetic field of a dipole reads: $${\bf B} = \frac{\mu_0}{4\pi}(\frac{3{\bf r}({\bf{m}}\cdot{\bf{r}})}{r^5}-\frac{{\bf m}}{r^3})$$ The first term vanishes in the plane perpendicular to the dipole. You can see that the resulting field drops off in strength cubically with distance. If the spins are arranged at equal intervals, then the interaction energy coming from next to nearest neighbors will be 1/8 of that coming from nearest neighbors. Since this is an order of magnitude smaller, it is reasonable to neglect everything but nearest neighbor interactions.