Time Viewer -

The Time viewer is a fictional device occasionally used in science fiction. It is usually a device which functions along the same lines as a television, except that the picture depicts events in another time, either the past or the future. The device is also often called a chronoscope, but this name has also been used by the Victorian scientist, Charles Wheatstone.

An apocryphal device called a Chronovisor is believed by some to exist already, and features in certain conspiracy theories.

Examples in fiction
In stories where time travel is a major plot element, the ability to view the happenings at another time is simply a side effect of the technology, and is rarely noted. An exception is "Millennium" by John Varley, where the time viewer's behavior (or misbehavior) is an important plot element. For reasons of "temporal censorship" the viewer cannot see into times where the travellers have been or will be, even if the location was far away. Also, the creation of a paradox results in progressive blurring of the image as alternate futures overlap.

Robert A. Heinlein's seminal time-travel story "By His Bootstraps" features a "time portal" with viewing capability, created by a future race of aliens which reduced humans to docile servants, ripe for exploitation by a 20th century go-getter. The protagonist eventually uses the viewer to see the aliens before they left Earth, but the experience almost unhinges his mind. It is while idly viewing his own home time period that he sets into motion the paradoxes that lead to him attaining his new life.

Other stories feature the time viewer, or some similar technology, as the principal plot element. The best known is "The Dead Past", by Isaac Asimov which concerns the clandestine creation of a time viewer when research into the subject is mysteriously suppressed. The reason for this is revealed at the end - the mere existence of a time viewer destroys all notions of privacy, since the device can be used to view events happening only a fraction of a second ago. A similar outcome features in Arthur C. Clarke's "The Light of Other Days". This aspect of the device is almost a "plot killer", because of the profound effects it has. It becomes impossible to use it as a "normal" feature of a society which we can understand.

"Private Eye" by Henry Kuttner writing as Lewis Padgett, dramatized for BBC Television as "The Eye", envisions a murder in a society where time-viewing makes it virtually impossible to commit one and escape punishment, but also which allows pleas of temporary insanity and self-defense. The protagonist instead schemes to get close enough to the victim, who has married the woman he thought he loved, that he can provoke an attack by the victim and kill him in self-defense. The murder weapon is an antique scalpel used as a letter opener, whose presence between them is carefully orchestrated by the murderer.

"E for Effort", a novella by T. L. Sherred, details a time viewer built by a poor genius who cannot get people to take him seriously, so he uses it to create historical movies which he then shows in his decrepit theater. He is discovered by a Hollywood producer, who is able to exploit the viewer to create first movies, then historical reconstructions, and finally political documentaries. The last part is his undoing, as he exposes every crime committed in the name of patriotism and ideology by world leaders, resulting in the collapse of government, and nuclear war.

With time travel

 * "By His Bootstraps" by Robert A. Heinlein.
 * Millennium by John Varley.
 * The End of Eternity by Isaac Asimov.
 * Pastwatch by Orson Scott Card.

Without time travel

 * "The Dead Past" by Isaac Asimov.
 * The Light of Other Days by Arthur C. Clarke.
 * "E for Effort" by T. L. Sherred.
 * "Private Eye" by Lewis Padgett (pseudonym of Henry Kuttner and C.L. Moore)
 * "Paycheck" by Philip K. Dick
 * The Brightonomicon by Robert Rankin (there called the "Chronovision")
 * "I See You" by Damon Knight