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Measure Gravity.

Drop a ball from different heights - see how long it takes to hit the ground from each.

Cut vitamins out of your diet and measure how long it takes to get scurvy

Coorilate the relationship between the amount of protein you eat and how fast your fingernails grow.

tape a cat's feet and see how long it takes it to adapt.

See how long it takes a nail to rust in a glass of water vs a glass of coke vs a glass of milk vs a glass of oil vs a glass of windex vs a glass of piss

test young people's hearing vs old peoples hearing. -my hearing cuts out at about 17000hz. god damn ipod.

Sound waves, the effect of sound waves on plants. Get some plants and have a radio playing at one for a est and another in quiet and see if it affects growth. You will want a fast growing plant for this. I would skip evolution, takes way too long for a noticeable change if any.