The history of the discovery of dark energy

Investigate and describe the history of the discovery of dark energy
Paper details:

Students will investigate and describe the history of the discovery of dark energy and discuss the implications of this force on the “fate of the universe”.

In 400 +/- 50 words (the suggested word limits for each section are only a suggestion), students should consider in a single essay format:

a) Briefly discuss the observations that have led to the conclusion that dark energy exists and what properties it possess.

b) Describe what the existence of dark energy implies to the evolution (fate) of the universe.