I was told that a Jew cannot be a passenger in a car on the Sabbath because s/he adds weight and causes the car to burn more fuel [an infraction of the laws of the Sabbath]. However, most observant people I know will open a refrigerator on the Sabbath without it being unplugged. This lets warm air in, and causes the refrigerator to use more electricity in order to cool down (i.e. it causes more fuel to burn). Can you please shed some light on this discrepancy?
This is actually a very complex question, but I’ll try and shed some light on it (even though it really requires a fuller response).
There is a concept called “grama“, which means “an indirect cause”. For instance, the action of opening the refrigerator is a “grama“, for the eventual response of the thermostat is to cause the motor to turn on. However, it is not an immediate/direct cause, and is, therefore, in this particular case, permissible.
And yet, causing extra fuel consumption by riding in a car is a direct and immediate cause of an action (e.g. the burning of fuel) that is prohibited on the Sabbath. Therefore, it is surely forbidden.