Question

Why radiant energy from the sun can heat objects and when the sun is not present heat may be lost.

Answer 1

http://openstudy.com/study#/updates/4f93682ee4b000ae9eca0912

Answer 2

this onef one stands near a fire without changing position, soon their clothes and skin will begin to become hot due to the RADIATION of infra-red energy from the fire source. This energy form travels in a straight line [unless reflected] from the source in all directions. When it comes in contact with an object which absorbs [does not reflect] it, in the process of absorbtion, the infra-red energy is converted to heat.
In the case of the Earth's loss of heat, it simply radiates into space where it continues to travel [like a ray of light, except invisible to the human eye] until it contacts some object.