I can be traced back to 3000bc, often go unnoticed, can be overhead, under feet or somewhere in between, evolution has changed me, am lighter than I used to be, and can protect your investment.
I would ask for another science teacher, this is not science. You deserve a quality education if you are paying for it. Teachers who give these to you as course work are wasting your time, in my opinion.
Helium
Based on the given clues, it sounds like you are talking about a shadow. Shadows can be traced back to around 3000 BC when ancient civilizations began to notice and study them. They often go unnoticed because they are formed when an object blocks light, creating a darker area on the ground or surrounding surfaces. Shadows can be found overhead, under our feet, or anywhere in between depending on the position of the light source and the objects in the environment.
Evolution can change shadows in the sense that as our technology and understanding of light evolved, so did our ability to control and manipulate shadows for various purposes, such as in photography or art. Furthermore, with advancements in modern materials, shadows have indeed become lighter than they used to be. For example, synthetic fabrics and lightweight materials are now used to create thinner and lighter shadows.
The reference to protecting your investment could suggest that shadows can be used as a security measure. For instance, strategically placed lights and shadows can help deter intruders or protect valuable property by creating the illusion of occupancy.
To arrive at this answer, I analyzed the given clues and knowledge about historical discoveries, light, and shadows. By paying attention to the context and combining these pieces of knowledge, I was able to deduce that you were referring to a shadow.