Why is making observations difficult?

Who started the 9 day fortnight? What is the normal temperature for 10 year old boy? What is the feet equivalent of 3 meters? What happens when you rub ebonite silk with a wool cloth? What are the 5 right and wrong application of science? What are all of the inventions that Chester Greenwood made? Why is it important to remain calm and in control at the work place? Why is habituation and dishabuation important to understand? Fluids exert pressure because they are made up of tiny? Is extra a common noun? How do you convert metric to standard? When a gas turns into a liquid it is? What climate do tornadoes usually occur in? Who first used observation as a way to understand the world? Why should the microscope be calibrated for each objectiveand prior to each use? Is chores a abstract noun? Who are some famous Native American scientists? What are the three types of motivation? When do you repeat an experiment? How much zeros are in a millimeter?