Why is the big bang a theory and not a fact?

Theories are well-founded explanations for describing events that occur in nature. They involve thoroughly tested hypotheses, facts and laws.

A theory may sound like a definitive explanation, but it may be overturned over the years.

In science, Fact typically refers to an observation, measurement, or other form of evidence that may repeat the same under different circumstances. However, scientists also use the term to refer to a scientific explanation that has been so tested and confirmed that there is often by far no convincing reason to continue testing or looking at additional examples.

Like all scientific theories, the theory of the Big Bang is subject to refinement as new areas of science emerge or new technologies emerge that allow observations and experiments previously impossible.

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.