Occasionally, scientists are forced to use a to represent the actual phenomenon, usually for ethical, financial, or logistical limitations.

What would happen to the tides if there was no moon and no sun in the sky?

Why did the athenians choose officials by lottery? would there be drawbacks to this method? explain.

Atraffic cop has pulled over a speeder, only to discover that he has stopped a close friend. the police officer is torn, because his professional obligations demand that he punish the speeder, but his personal obligations suggest that he should give a friend a break. what is this called?