A Heisenburp device is an object which can detect the passage of a spaceship without affecting the spaceship's path or timing. The name is a reference to Werner Heisenberg's Uncertainty Principle, a principle in quantum physics which states that it is physically impossible to detect a particle without affecting it in some way; it was coined by Bill Gosper. The first Heisenburp device was constructed by David Bell in December 1992.
Some Heisenburp reactions do affect the spaceship, but only for a few generations, after which it evolves as if it had never been affected. Such reactions have generally been called "pseudo-Heisenburp" reactions, since the discovery of "pure" or "true" Heisenburp reactions where the spaceship is not even temporarily affected.
The first Heisenburp on the left is a glider Heisenburp (for the south-west glider in the glider cluster), reacting with a pi-heptomino, the Heisenburp device. The glider passes the Pi at T=18. The glider is not affected, but the pi's evolution changed to produce an Eater 1. At gen 18, the glider acts as a rock. The glider's spark causes the Eater 1 to be produced.
Heisenburp devices can be used to not just detect gliders, but also other spaceships such as MWSS, HWSS and Sir Robin. The Heisenburp on the right is a combination of an HWSS and glider Heisenburps. The active reaction of the second Heisenburp (right) is a Herschel.
- Top left -- Generation 0: The purple HWSS and glider of the spaceship cluster will be used. The HWSS will convert the green Herschel to a pi-heptomino (with the help of the blue ship catalyst) shown by the house in cyan, then the glider will change the evolution of the house to make an eater 1 and block (which is the same reaction as the first heisenburp device).
- Left -- Generation 21: The purple HWSS gives out its spark, changing the evolution of the Herschel. The image ignores the Herschel's first natural glider, which will escape south-westwards.
- Bottom left -- Generation 108: The HWSS cluster glides off to the north undamaged; the purple HWSS was not even temporarily affected. The blue ship comes into play and will eat the semi-traffic light on the south.
- Top right -- Generation 115: The house (green) has appeared. The purple glider is in the position to be detected. After detection, the house will evolve into the pink eater 1 and block. The blue ship recovers in 6 generations.
- Right -- Generation 130: This is basically the same as T=18 on the first Heisenburp. The glider's spark changes the pi-heptomino's evolution.
- Bottom right -- Generation 165: The process is complete. The eater 1 and block have appeared. The purple glider was not even temporarily affected. The glider cluster drifts off north-eastwards.
Below the image is the LifeViewer version, which uses "ghost" house, "ghost" eater 1 and "ghost" block as markings.