Where was runner A located at t = 0 s? Which runner was ahead at t = 48.0 s?

When runner A was at 0.0 m, where was runner B?

How far apart were runners A and B at t = 20.0 s?

Independent variable is something that is changed in a experiment. 

Because the sun is the biggest and if the sun orbits the earth we will be dead probably

It maybe because uranus is made of gas but uranus has a solid core in the middle

Answer;

hot magma rises and pushes up toward the lithosphere, and as it cools it cycles back down toward the core to be heated again.

explanation; convection currents are the circular pathways taken by a fluid that enhances heat transfer by the process known as convection which occurs in fluids.convection currents transfer heat from one place to another by mass motion of a fluid. earth mantle is in a semi-liquid state and behaves like any other fluid, rising up from the bottom of the mantle after becoming hotter and less dense from heat of the earth's core, as the rock loses heat into the earth's crust it becomes cooler and more dense, then sinking back down to the core, then repeating the cycle.