Me and my grandfather got into a "debate" (more like one-sided argument) on whether objects fall at the same rate on earth independent of air resistance or not. He claims that "If you drop 2 objects from an airplane -- like a car and a marble, both objects would hit the ground at the same time.", I say no, because the car has a larger surface area and the marble would hit first due to less air resistance (Neither of us really know anything about physics [that's why I'm here]). I've sent him tons of links on the subject but he's still determined he's right because "that's the way he was taught in school". There's not many high places here for me to drop 2 objects off of to see the results, so my question is: How high must we be to be able to observe a noticeable difference in when the two objects hit the ground? How do I calculate the approximate difference of objects hitting the ground? For simplicity let's say the 2 objects I am dropping are: a 2kg 1m square, and a 2kg 1m diameter sphere.