First of all, let me start by saying that I am quite uneducated when it comes to physics (not even as much as a high school physics course), so please be gentle with me. I wouldn't even be at your lovely forum, but this question has been driving me nuts, and no one else seems to answer it to my satisfaction. Thanks in advance for any help you provide. ------------------------------------------- Do all objects fall at the same speed or not? I've been deeply confused over this issue for some time. The conventional answer is that, yes indeed, all objects do fall at the same speed. The acceleration of an object depends upon the force of gravity and the mass of an object. A more massive object will require more force to accelerate at the same speed as a less massive object, and gravity will act with greater force upon a more massive object. The conflicting points exactly cancel each other out, such that all object accelerate at the same speed. But if I accept this, I am confronted with a wide range of paradoxes I can't explain. I'll list three of them: 1) If I were to drop a bowling ball toward the Earth, it would fall at a certain rate. If I were to drop the same ball toward the Moon, it would fall at a slower rate. Correct? The more massive the object (Earth vs. Moon), the greater the force of gravity and the greater the rate an object will accelerate tworads it due to gravity. Correct? But why should I use the Earth or the Moon as my frame of reference? Why can't I use the bowling ball as my frame of reference, and drop the Earth and the Moon towards the surface? In that case, we already know the Earth would fall faster twoard the bowling ball, and we know this is *because* of the greater mass of the Earth. So "heavier" or more massive objects do fall faster, don't they? 2) I saw on a physics website an equation that is used to determine the mass of a planet by setting an object in orbit around it. The speed with which this object orbits the planet determines the mass of the planet, but cannot (according to the site) determine the mass of the orbiting body- to do that you would have to set some other object in orbit around the first object. Why? Because, says the site, all objects, no matter the mass, will orbit at the same speed. So let's assume that we are sitting on an object in a universe devoid of anything other than the object we are sitting on and a body orbiting us/our object. We can use this body to determine the mass of the object we are on (pretending we are devoid of mass ourselves). Correct? So what if I said the object we are on is a satalite used by NASA and the orbiting body is a planet? Again, what object is orbiting what is simply an arbitrary frame of reference. I can just as easily choose the satalite as the object being orbited as I can the planet! And in doing so, I would come to the exact conclusion that the site says I can't- determine the weight of the object doing the orbiting. What has gone wrong here? 3) There was a debate for a long time regarding whether or not the universe would continue to expand forever or would collapse back in on itself. It was argued that if there was enough mass in the universe, it would collapse, and otherwise it would continue to expand. If mass is not important to the acceleration of two objects towards each other, why would it matter how much mass is in the universe at all? It seems the argument requires that more massive objects accelerate faster than less massive objects. Is the whole idea of "all objects fall at the same speed" just bogus? Are the intro physics books simply wrong or oversimplifying the issue? What am I missing here?