Question

why is the sun main source of heat and light

Answer 1

Because sun is hot .
Sun have light and heat .
Sun is very hot

Answer 2

The sun is the main source of light and heat for things living on Earth. The sun is the main source of heat and light for living things on earth.The Sun is undergoing nuclear fusion of Hydrogen. The mass loss resulting from this nuclear reaction is energy which is transmitted to us in the form of Photons.