Some good ideas for science fair projects include recording the effects of different foods on the human heart rate, observing the influence of phrasing questions differently on the answers they elicit, paper airplane engineering, coin toss probabilities and an investigation of platonic solids. Science fair projects can be conducted within virtually any branch of science, including biology, chemistry, physics, mathematics, engineering and the behavioral sciences, such as psychology or sociology.
Astronomy is often a popular area to focus on. There are project ideas in this field ranging in difficulty level and time required. An example of a relatively easy astronomical science fair project could be to investigate the origin and nature of Saturn's rings using a record turntable to simulate the conditions of their formation. This experiment is neither expensive nor time consuming and has no associated safety issues.
A more challenging approach to an astronomy science fair project could involve the recreation of early stargazing and mapping techniques.
Some projects might straddle scientific disciplines rather than fall neatly into a single one like astronomy. Science fair projects involving the creation of electrical circuits, for example, often incorporate elements of mathematics, logic and physics. Similarly, creating an optimal paper airplane by trial and error engages skills and knowledge of geometry and physics.