The computer trackball was invented 17 years before the computer mouse
In 1946, British engineer Ralph Benjamin invented the trackball for a radar plotting system called DATAR. Using a rubber-coated ball resting against internal rollers, it allowed operators to position a cursor on a radar screen. Douglas Engelbart would not invent the computer mouse until 1963, making the trackball its direct historical predecessor.
Radar Displays and the Birth of Screen Cursors
In the aftermath of the Second World War, military command centers faced an unprecedented data problem. Early radar systems could sweep skies and sea lanes to locate distant targets, but processing that positional data required human operators to manually calculate vectors, mark transparent plotting boards, and relay coordinates over voice channels. As aircraft speeds increased in the late 1940s, manual plotting proved far too slow to track fast-moving threats in real time. Navies and air forces required electronic systems that could present dynamic target data directly on cathode-ray tube displays.
Displaying targets electronically solved only half the challenge; operators still needed an efficient, intuitive way to interact with points of light on a screen. Entering coordinate numbers via keyboards or mechanical dials was clumsy and slow, while analog joysticks presented mechanical spring-resistance issues and struggled with precision. Engineers needed an input device that allowed continuous, omnidirectional movement across two dimensions, translating natural physical gestures directly into precise coordinate shifts on a screen.
Ralph Benjamin and the British Comprehensive Display System
The earliest solution emerged in 1946 within the British Royal Navy Scientific Service. Engineer Ralph Benjamin was developing the Comprehensive Display System (CDS), a naval project designed to automate target tracking. Benjamin realized that an operator needed a smooth, multi-directional controller to steer a target cursor over radar blips. He devised a system he described as a 'roller ball'—a metal or rubber-coated sphere housed in a socket, resting against internal sensing rollers.
Benjamin's design allowed the operator to place their hand over the exposed top of the sphere and spin it freely in any direction. As the ball turned, its surface rotated two orthogonal wheels mounted inside the enclosure at right angles to one another. These wheels drove potentiometers or mechanical contacts that generated electrical signals corresponding to movement along the horizontal X-axis and vertical Y-axis. Benjamin filed a patent application for his roller ball device in 1947, creating the world's first pointing device for electronic computer displays, though the technology remained classified as a military secret for years.
The Canadian DATAR Project and Bowling-Ball Hardware
A few years later, across the Atlantic, an independent trackball invention was created for the Royal Canadian Navy. In 1952, engineers Kenyon Taylor, Tom Cranston, and Fred Longstaff were developing the Digital Automated Tracking and Resolving system, known as DATAR. DATAR was an ambitious tactical network designed to link multiple naval vessels over radio frequencies, allowing ships to share radar tracking data and form a unified battle picture in real time.
To allow operators to designate and select radar targets on cathode-ray tube screens, Kenyon Taylor and his team designed their own trackball mechanism. Rather than manufacturing a specialized spherical component from scratch, the team famously repurposed a standard five-pin Canadian bowling ball made of hard plastic. Mounted within four internal rollers, the smooth bowling ball provided enough weight and inertia to spin smoothly while operators marked target locations. Because DATAR was a classified military project, its trackball design was not patented or commercialized for the civilian world at the time.
Mechanical Mechanics: How a Trackball Senses Space
The underlying mechanics of early trackballs relied on fundamental geometry and mechanical linkage. A sphere can rotate along an infinite number of axes simultaneously, but any arbitrary rotation on a flat surface can be broken down mathematically into two perpendicular vector components: X (horizontal) and Y (vertical). By resting the sphere against two pickup rollers positioned at a ninety-degree angle from each other, the mechanism mechanically decomposes complex, diagonal rolling motions into two separate rotational inputs.
Early implementations connected these pickup rollers to analog potentiometers that modulated electric voltages based on rotational angle. As digital computing advanced, these were replaced by slotted encoder discs coupled to optical sensors or mechanical brushes that generated pulses as the wheel turned. Counting the frequency and sequence of these pulses allowed the host computer to calculate both the speed and direction of the cursor. Because the trackball sat stationary on a console, it bypassed the tracking boundary issues that later plagued moving pointing devices, offering infinite scrolling capability in a fixed physical footprint.
The Inversion: From Stationary Trackball to Desktop Mouse
For nearly two decades, the trackball remained the primary method for two-dimensional screen manipulation in specialized military and industrial environments. It was not until 1963 that Douglas Engelbart and his team at the Stanford Research Institute developed an alternative concept: the computer mouse. Engelbart's original prototype used two perpendicular wooden wheels protruding from the bottom of a handheld block, which tracked movement across a flat desktop rather than having a user manipulate a stationary sphere directly.
Later mouse designs by researchers, including Bill English at Xerox PARC and the German firm Telefunken, effectively inverted the trackball. Instead of keeping the housing stationary and rotating the ball with fingers, they placed a rubber-coated trackball underneath a palm-sized housing so that dragging the device across a desk forced the internal ball to turn against pickup rollers. In this sense, the classic mechanical computer mouse that dominated personal computing throughout the 1980s and 1990s was fundamentally an upside-down trackball adapted for desktop mobility.
Enduring Roles in Arcades, Laptops, and Ergonomics
While the mouse became the standard pointing device for mainstream desktop computers, the trackball carved out durable niches where free desk space was unavailable or extreme precision was required. In the late 1970s and 1980s, trackballs entered consumer culture through popular arcade games such as Atari's Missile Command and Centipede, where the physical inertia of a heavy, freely spinning ball provided high-speed responsiveness that joysticks could not match.
During the early era of portable computing in the 1990s, before smooth capacitive touchpads became widespread, many laptop computers integrated small trackballs next to the keyboard or screen to eliminate the need for an external mouse. Today, trackballs remain widely used in air traffic control centers, naval command consoles, computer-aided design (CAD) workstations, and audio mixing studios. Their stationary nature eliminates repetitive arm motions and wrist strain, preserving the core utility of a device invented decades before the personal computer existed.
Key takeaways
•British engineer Ralph Benjamin invented the trackball in 1946 as a 'roller ball' interface for the Royal Navy's Comprehensive Display System radar project.
•In 1952, Canadian engineers building the DATAR tactical naval system independently constructed a trackball input using a standard five-pin Canadian bowling ball.
•Douglas Engelbart's 1963 computer mouse arrived 17 years later, and later mechanical ball mice were essentially inverted trackballs designed to roll across a desk.
•Trackballs work by resting a free-spinning sphere against two orthogonal internal rollers that mechanically split movement into X and Y coordinate signals.