It's the difference between knowing you're hungry and knowing you will be hungry. I can tell you that if I drive a car far enough it will eventually run out of

It's the difference between knowing you're hungry and knowing you will be hungry. I can tell you that if I drive a car far enough it will eventually run out of gas, so I should probably go to the gas station before a big trip. But that's a very different problem from having a gas gauge that's broken entirely.