A STRAIGHT LINE may be the shortest distance between two points, but it is not necessarily the safest. Workers who drive or unload a transport truck or forklift, work around a loading dock on platforms or ladders, or perform any task designed so that it invites an opportunity to jump down may find it expedient, unavoidable or necessary to take that quick route down. Regardless of the task, potential hazards, personal goals or levels of risk tolerance, what goes up does come down with increased risk for injury. Gravity is relentless and it remains unwavering and indifferent to personal well-being. Challenge the laws of gravity and Newtonian mechanics, and the outcome just might be grave. "Gravity is a relentless companion, both friend and foe, always on duty" (Gonzalez, 2004).
Sir Isaac Newton, the brilliant and enigmatic 17th century British scientist who was sometimes slow to learn from his experiences, teaches a valuable hazard-awareness lesson. As the tale goes, he discovered gravity when he observed an apple falling from a tree. That may not have been the whole story, for another---perhaps tall---tale described his flash of insight in a slightly different light. Allegedly, the bystander reconstructed the scene as follows: The way I heard the story, Mr. Newton was riding in a surrey through an apple orchard. Wanting one of those juicy ripe red apples, he glanced around and not spying the landowner, jumped down from the seat, only upon landing to twist his ankle. He then uttered, to my amazement, a few choice English expletives that I theretofore heard only from the whiskey-soaked jowls of Bristol dockworkers. He then hobbled over and sat down against one of those apple trees, only to then again slip afoot, poor chap, and bump his head hard against said tree dislodging a ripened apple that, by Providence no doubt, fell and opportunely hit him squarely on the noggin. Such foul words again poured from the mouth of that respected scientist as he raised high his fist as if to challenge the tree-spirit for that rude and unwelcome thumping. He spoke aloud not aware of my presence, "Any more assaults on my body this day will put me in an early grave!" From that episode, the word gravity entered the English lexicon and Newton went on to explain mathematically why that apple fell and make several other monumental discoveries.
Building on those lingering painful memories, combined with other observations of the natural world, Newton ultimately derived his universally applicable laws of motion (USOE):
First law: A body in motion tends to stay in motion unless acted upon by an unbalanced force (or a body at rest tends to stay at rest).
Inertia is another way to describe this phenomenon. Imagine driving a car and abruptly slamming on the brakes (action). You feel your body continue to move forward (reaction), held in place by the (hopefully) buckled seatbelt's friction between body and car seat, and hands on the steering wheel.