Question

When using science to investigate physical phenomena, which characteristic of the event must exist

Answer 1

I think you forgot to give the options along with the question. I am answering the question based on my research and knowledge. "Observable" is the one characteristic of event that must exist when using science to investigate physical phenomena. I hope that this is the answer that has come to your help.

Answer 2

When using science to investigate physical phenomena, the characteristic of the event that must exist is OBSERVABLE.

Scientific investigation is usually initiated when a scientist observed a phenomenon, which he did not have an explanation for. Observation is a very important principle in scientific investigation and usually give birth to hypothesis and experiments. When a scientist observed a phenomenon he does not have an answer to, he formulates a hypothesis about his observation and proceed to carry out experiments in order to determine whether his hypothesis is wrong or right.