Impression materials

Behavioral imprinting is observed in some newborn animals and occurs when they develop strong and specific attachments to another animal (usually a parent) following brief, early-life exposures. Offspring imprint onto parents within a brief period after birth or hatching; this time window is called the critical period. Once imprinting occurs, the bond established between the parents and their offspring is usually long-lasting.

German physicist Wilhelm Röntgen (1845–1923) was experimenting with electrical current when he discovered that a mysterious and invisible "ray" would pass through his flesh but leave an outline of his bones on a screen coated with a metal compound. In 1895, Röntgen made the first durable record of the internal parts of a living human: an "X-ray" image (as it came to be called) of his wife’s hand. Scientists worldwide quickly began their own experiments with X-rays, and by 1900, X-ray was widely...

According to Newton’s second law of motion, the rate of change of the momentum of an object is the net external force acting on it. The total change in momentum between two timepoints thus depends on both the external force acting on it and the time over which it acts. Describing this mathematically, the total change of an object’s motion is proportional to the force vector and the time over which it is applied. This product is called impulse.
Additionally, it can be shown that the total...