Scientists discovered this new optical illusion. Try focusing on the red cross while the dots move. The are moving all around isn't it? Except they aren't. All of them are moving "in straight trajectories and random directions without colliding."
In this paper, we report on a novel visual motion illusion. When hundreds of dots move in straight trajectories and random directions without colliding, the trajectories are perceived as wriggling rather than straight (bottom). We examined the nature of this "wriggling motion trajectory illusion" via six separate experiments. The illusion was most pronounced when there were a large number of dots (top). The illusion was independent of both the distance covered (Experiment 3) and the observer's eye movements (Experiment 4) as well as the dot types (Experiment 5). We also showed that the proximity among the moving dots plays a role in the illusion (Experiment 6).
Focus on one dot and you will see it going on a straight line. Take a look at the cross and you'll see the dots moving all over the place.