The First Law of Motion, formulated by Isaac Newton, states that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity unless acted upon by an external force. This principle highlights the concept of inertia, which is the tendency of objects to resist changes in their state of motion. In practical terms, this means that if you slide a book across a table, it will eventually stop due to the friction between the book and the table. Similarly, a ball thrown in space will keep moving indefinitely unless a force, like gravity or collision, alters its path.