Proof that Objects Fall at the Same Rate

Salv. But, even without further experiment, it is possible to prove clearly, by means of a short and conclusive argument, that a heavier body does not move more rapidly than a lighter one provided both bodies are of the same material and in short such as those mentioned by Aristotle. But tell me, Simplicio, whether you admit that each falling body acquires a definite speed fixed by nature, a velocity which cannot be increased or diminished except by the use of force [violenza] or resistance....

 Science Manipulates Language to Make it More Precise

Let us consider two spheres moving in different di- rections on a smooth table. So as to have a definite picture, we may assume the two directions perpendicu- lar to each other. Since there are no external forces acting, the motions are perfectly uniform. Suppose, further, that the speeds are equal, that is, both cover the same distance in the same interval of time. But is it correct to say that the two spheres have the same velocity? The answer can be yes or no ! If the speedo- mete...

 Big Whorls, Little Whorls

Big whorls have little whorls Which feed on their velocity And little whorls have lesser whorls, And so on to viscosity.

 The Enterprise's Impulse Drive

Moving back to the sub-light-speed world: We are not through with Einstein yet. His famous relation between mass and energy, E=mc 2 , which is a consequence of special relativity, presents a further challenge to space travel at impulse speeds. As I have described it in chapter 1, a rocket is a device that propels material backward in order to move forward. As you might imagine, the faster the material is propelled backward, the larger will be the forward impulse the rocket will receive. Mater...