Final answer:
Hadley's S Curve relates to sustainability and energy in AP environmental sciences, referring to a curve with a positive slope and discussions around renewable energy sources and economic behaviors.
Step-by-step explanation:
The concept of Hadley's S Curve appears to relate to a discussion surrounding sustainability and energy sources, particularly in an economics or environmental sciences context within the Advanced Placement (AP) curriculum. When the question refers to a curve being positive, it is likely referencing the positive slope of the curve, indicating an upward trend over time. The question seems to derive from a chapter discussing future energy prospects, with the renewable alternative being an optimistic scenario that maintains a constant energy supply, avoiding a decline in physical sector scale. Further context refers to elements such as energy density and economic behaviors not aligning with U.S. trends, which could influence the shape and trajectory of the curve.
A landmark in this context may refer to a notable point on the curve where significant changes in energy policy or technology occurred. The discussion about something that enabled and then disappeared might relate to a energy source or technology that was initially promising but later became unsustainable or obsolete. It contrasts with the idea of an ideal scenario, suggesting real-world conditions that deviate from theoretical models.
It's important to understand these concepts, especially when discussing sustainable futures and energy transitions, which are significant topics in advanced environmental studies courses.