Hi Kevin,

This is a good question. Some of the energy does dissipate, but it is a very small part of the process. There are very few particles in a given region in space. This is the same as saying the density is small. In fact there is about 1 particle in most any cubic centimeter out in the solar system. A cubic centimeter means a region in space with height, width, and length all equal to 1 centimeter. So the particles practically never collide with each other and dissipation, like with fluids or gases, doesn't happen within the solar system.

However, the small dissipation I mentioned above, does occur but it is related to the fact that these solar particles are charged and they can "sense" each other from far distances. So some dissipation can occur but over long distances and not enough to stop the particles from reaching Saturn or Uranus.

Laura