The classical mechanics described by Sir Isaac Newton begins to break down at very high velocities, i.e. at velocities near the speed of light \(c=299,792.458 \mathrm{~km} / \mathrm{s}\). For bodies m...The classical mechanics described by Sir Isaac Newton begins to break down at very high velocities, i.e. at velocities near the speed of light \(c=299,792.458 \mathrm{~km} / \mathrm{s}\). For bodies moving at a significant fraction of the speed of light, Newton's mechanics needs to be modified. The necessary modifications were developed by physicist Albert Einstein in the early 20th century, in a theory now called the special theory of relativity.
