2+1 is not always 3: In the microworld unity is not always strength

In the microscopic world, as long as there are only two particles, things are relatively simple. When other particles are introduced, however, the situation soon becomes more complicated. Imagine there are two people pushing a broken-down car: The total force is the sum of their forces. Similarly, if there are three people, the total force would be the sum of the force of these three people, and so on. Now imagine a colloid, a solid particle of a few thousandths of a millimeter, immersed in flui