A changeable factor in an experiment is referred to as a

the animal that would be cutest if scaled down to the size of a cat? elephant

for example, no new evidence will demonstrate that the earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the earth is not divided into solid plates that have moved over geological timescales .