Hello, I've been watching too much anime. I know that isn't the best way to ask a question scientific in nature, but visualizing bizarre situations is one of the best ways to come up with interesting questions. Anyways, in order to break a rock by compressing it with your hands, you would need to apply force on the rock, right? Force is determined by mass times acceleration, right? I guess I can't change the acceleration of my hand when I try to press down on the rock, so in order to apply more force, I'd need to change the mass, right? (Here a little note: I assume that you can indeed change the acceleration, I can't imagine how I would in this scenario, but I assume you can.) So, back to changing the mass. Mass is defined by volume and density, right? I want to keep my size, so let's say that volume can't change in this equation, so what would need to change would be density, isn't it? But If I increase the density, I also increase the mass. If I increase the mass, I increase the weight (on earth), and if I do that, then my hand, which keeps getting heavier, will be pushed towards the ground or even rip my skin, break my bones and fall to the ground on its own. I would like to avoid that. So, lets say that not only the hand but the whole body gets denser uniformly. Then: 1) Would an denser hand be indeed able to break a rock by applying pressure on it? 2) If the whole body got dense enough to be able to break a rock by trying to compress it, would it be able to keep its structure? I mean, would limbs collapse under their own weight, or would the body keep whole? and 3) If the body got dense enough to break a rock, would it also mean that it'd go through the planet due to it's own weight? Or is the ground able to withstand the weight? (Keep in mind that we would be talking of a human-shaped object that would weight, well....a lot. ( I guess I should be adding numbers to this) Well, that would be what's been bothering me. I know it's a waste of time since matter can't change it's density just like that, but... mmmm.... Can I change the mass of something by changing it's density, but without changing it's volume? I don't think it can be done, right? I mean, the density of something is inherent to it's enviromental conditions and it's state, right? (Whether it's a solid, a liquid, a gas...and conditions such as temperature etc.) Ok, no. It's too complicated now. Simply help me answer the three first questions, and if there is a way in which I can change the density of something without altering it's volume, please let me know.