Why does water ripple when you throw in a stone?

Question

Why does water ripple when you throw in a stone?

Answer 1

Displacement

Answer 2

When the stone hits the water some energy is transferred to the water.  Also a volume of water  equal to the size of the stone is displaced.  Water can not be compressed so the displaced water is forced up, this is the ripple above the level of the water.  The energy of the moving stone determines the size.  The secondary ripples are a result of the water rushing back in to fill the hole in the water to stone and outward moving ripples left behind.  Often you can see a drop of water be ejected when the water rushing in collides. When it falls it will start a new wave train, much smaller then the original.  The ripples then are a result of dissipating energy and displaced water.

Answer 3

The energy of impact is dispersed as waves.

Answer 4

Because if it didn't it would be ice

Answer 5

Ripples are certainly not zoological! The surface of a liquid is not a fixed sheet, but can be deformed. The deformations can be described by mathematical equations which are actually quite complex. Fortunately, for relatively small deformations, the equations give a solution in terms of well-behaved waves, and these are what are commonly called ripples. When you throw in a stone, you suddenly change the configuration of the surface, and setting this as an initial boundary condition leads to a solution of the equations which describes ripples travelling outward.

For your interest, some of the other possible solutions of the equations when the disturbances are not small include the breaking waves that you get in severe storms, and the tsunami or "tidal waves" due to earthquakes. It's an interesting branch of physics!