Does the plants think the light bulb is the Sun?? how does the HPS light make the plant grow??? (yes i know its a grow light but what is the process) what exactly is going on when the light is off (am pretty sure they still growing)??? for example:- i only have baby plants, when i switch my HPS 400w light on then after 8 hrs i notice a change in the plants appearance then when i switch it off then go back to it again a few hours later the plant seems taller i thought plants didnt grow in the dark so id love to know whats going on there???