Because a raindrop is a small, slightly oval glob of water. The vertical streak you see is basically motion blur; it’s small enough and moving fast enough that your eye can’t see the distinct object, just the path it takes.
When you’re driving in a car, you’re moving fast enough forward that the raindrops appear to be moving towards you as they fall. Hence, they appear to be falling diagonally or have a “slanted” shape. But in reality, it’s the same shape as before, and it’s just your eyes tricking you.
Latest Answers