IDEAS FOR THE SRP

Well, I've been looking at ideas for a long time, and I've finally come across a few that I think are pretty interesting. Actually, originally I had a lot of ideas, and they generally fell into the categories of Biology, Chemistry and Engineering. These branched off into various branches, like health science, astronomy, environmental science and so on. I've been having trouble trying to narrow down my list of ideas but these are the ones I'm most interested in:

ENGINEERING:

• How and what materials are the best to make a working telescope
• How to build a sensor to detect the presence of a magnetic field
• How to make a working solar panel
• How to build a working electrochemical battery and how it can be made more efficient, with a highter output

HUMAN BODY:

• How caffeine affects the body - our typing speed and accuracy, body temperature, breathing rate, heart/pulse rate etc.
• Whether the absence or presence of a net affects a free throw in basketball
• Whether energy bars/energy drinks/sports drinks affect performance, and whether or not different energy bars have different levels of efficiency - affect reaction time, energy level etc.

PLANTS AND ENVIRONMENTAL:

• Whether magnetism affects the growth of a plant, and whether the position of the magnet or a magnetic field affects the plant growth or the germination of a plant
• Whether watering a plant with water containing caffeine affects the plant, and whether watering the seed with caffeinated water affects germination
• Whether ash can enhance plant growth and what plants grow best in ash and soil combined
• What chemicals affect algae in what ways, and what is best for algae to grow
• What different factors affect germination of a seed
• How different soils are affected by erosion OR how different erosional techniques affect a certain type of soil
• Whether pH of rain varies according to the season

FOOD:

• Whether different types of mould grow on different kind of bread, and what conditions cause what bacterial growth fastest etc.
• Whether storage temperature, type of storage, and time affect the pH of different kinds of juice
• Test bottled water for impurities and compare the impurities (e.g. lead) between different brands of bottled water, and whether there is evidence of leaching of hazardous chemicals from the plastics of the bottle over time

It's still a lot of ideas, but I am particularly interested in building something, like a telescope or a solar panel, but I'm not sure whether or not it's a good idea to choose something like that. The ideas above are the ones I like the most, but I don't know which to choose. If anyopne has any opinions or advice they can give me on what might be the best idea, I'd really appreciate it.