How do scientists develop scientific explanation about subjects that are impossible brought controlled experiment?

How was the toster invented? A diver goes down to a depth of 132 feet How many atmospheres of pressure are on the diver? Why do birds and mammals have four chambered heart? What type of fossil is found in a hollow place shaped like an organism? What are the components of an investigatory process? Variables in an experiment whose effect you are testing? What is the first thing you should do when solving a problem in science? What is the most common unit for density? Why does it foam when you add salt to coke? Is centiliter bigger than milliliter? What are example sentences for recycling at school? What do unicellular organisms drink? What is often the next method of characterization that helps add depth to the first method? What is a charged atom? What is a synonym for repellent? If a violent criminal group uses military force to take control of entire regions of a country. Which statement best describes the group in the passage? What did Charles Watson Sr invent? What makes up most of the volume of blood plasma? What is the melting point of distilled water? What is the story of the discovery of Oxygen?

How do scientists develop scientific explanation about subjects that are impossible brought controlled experiment?