Item from Foundation by Isaac Asimov
Handheld device containing the complete equations of the Seldon Plan — only Second Foundationers can read or modify it. A glowing mathematical display that holds the galaxy's future in symbolic notation.
The Prime Radiant is the Seldon Plan in physical form — every equation, every prediction, every branching probability encoded in a device small enough to hide in a pocket. Only the Second Foundation's Speakers can operate it, and only the First Speaker can authorize changes to the plan's core equations. This restriction is not technological but mentalic: the device reads the user's mental patterns and responds only to those trained in the Second Foundation's disciplines. Modifying the plan is the Second Foundation's most solemn responsibility. When the Mule disrupted psychohistory's predictions, the Second Foundationers had to recalculate — adjusting thousands of interlocking equations to account for damage already done and chart a new path to the same destination. The work took years and required intellectual courage: admitting the plan was broken, understanding how, and finding a mathematical path back to viability. The Prime Radiant is also a test of character. Anyone who holds it holds the future — the temptation to adjust the plan for personal benefit, to steer civilizations toward preferred outcomes, to play god with mathematical sanction. The Second Foundation's internal discipline exists primarily to resist this temptation, and the few who succumbed were dealt with by their colleagues with quiet, permanent efficiency.
A small, featureless sphere that fits in one hand — dark metallic surface, warm to the touch, with no visible controls. When activated, it projects a three-dimensional field of glowing equations that fill the surrounding space. The user navigates by mental command — zooming into equation clusters, following causal chains, adjusting variables. The display responds to trained mentalic input; to an untrained mind, the controls are invisible and the equations are meaningless notation. The light it produces is steady, white-gold, and casts no shadows.
Also known as: the Radiant, Seldon's Prime Radiant