Question

Y does temperature increase as we go down d earth

Answer 1

As you move further underground, stuff gets crushed by the weight of everything on top of it (gravity). As it gets crushed we say the pressure increases. Pushing all the molecules closer together and increasing the pressure causes the molecules to move faster, which is what we have defined as being hotter.

Answer 2

when we go inside the Earth temperature increase  because some  radioactive substances inside Earth release energy and this result in increase in temperature.