In science fiction, a time viewer, temporal viewer, or chronoscope is a device that allows another point in time to be observed.[1] The concept has appeared since the late 19th century, constituting a significant yet relatively obscure subgenre of time travel fiction and appearing in various media including literature, cinema, and television. Stories usually explain the technology by referencing cutting-edge science, though sometimes invoking the supernatural instead. Most commonly only the past can be observed, though occasionally time viewers capable of showing the future appear; these devices are sometimes limited in terms of what information about the future can be obtained. Other variations on the concept include being able to listen to the past but not view it.
One reason authors may choose to write about time viewers rather than time machines is to circumvent the issue of temporal paradoxes. Recurring applications include studying history, solving crimes, and entertainment in the form of displaying historic events to an audience. Because the past includes events as recently as the previous second, privacy may be compromised by such devices; several stories explore the implications thereof. Other stories examine the effects of being observed by onlookers further into the future. An unanticipated influence on past events is a common motif in stories about time viewers, and exploiting this side-effect appears in some stories.
Concept
In its most basic form, a time viewer is a device that only allows the observation of the past.[2]: 97 Unlike with a time machine, the user is not transported from one moment in time to another.[3][4] Under the strictest definition it cannot alter the past;[2]: 97 [3] however, the unexpected discovery that the device does indeed affect the past is a common motif.[2]: 99 [3] Variations on the concept where the future rather than the past is observed are more uncommon but nevertheless appear in multiple works.[3][5]: 128 Another variation involves listening to the past rather than viewing it.[2]: 97–98 [3]
The earliest known example of a fully fledged time viewer in fiction appears in the 1883 short story "L'historioscope" by Eugène Mouton in the form of an electrical telescope, though it was prefigured by a couple of proto-variations on the concept;[3][8][9] in the 1872 work Recits de l'infini (which later turned into the 1887 novel Lumen) by Camille Flammarion a spirit accomplishes the same effect by travelling faster than light, and the titular device in the 1873 short story "The Automaton Ear" by Florence McLandburgh enables listening to the past.[3][8][10]: 251 In film, the first time viewer appeared in the 1918 film The Ghost of Slumber Mountain.[3] The concept has appeared regularly in works of fiction ever since, creating a sub-genre within time travel fiction, but remained comparatively obscure.[2]: 97 [6]: 57–58 [7]: 71 [11]: 532–533
Narrative function
Science fiction author Stephen Baxter identifies several different ways time viewers are used in fiction. The most basic premise is of the time viewer as simply a "neat gadget", with a common variation being something going wrong, typically the past being unintentionally altered. Changing the past on purpose is another recurring application. According to Baxter, the wider implications of the existence of time viewers are sometimes explored in hard science fiction by performing what's known as a PEST (Political, Economic, Social, and Technical) analysis.[2]: 98–99, 101
Several authors consider time viewers to be inherently more plausible than time machines. Science fiction author Damien Broderick says that "using a time viewer is in essence no more absurd than watching a movie made 50 years ago" since the past cannot be affected by it.[7]: 71 Baxter similarly says that time viewers are more extrapolation than fantasy, comparing them to archaeological research.[2]: 97 For this reason, science writer Paul J. Nahin and physicist Stephen Webb say that a benefit for writers is being able to write time travel stories without needing to consider the possibility of time paradoxes;[5]: 128 [6]: 57–58 Nahin nevertheless notes that interacting with the past via a time machine, or even affecting it, does not necessarily cause paradoxes.[6]: 57
Themes
Studying history
Time viewers are sometimes used to observe moments in history that are similarly popular destinations for time travel in fiction, one example being the crucifixion of Jesus in the 1904 novel Around a Distant Star by Jean Delaire [Wikidata].[11]: 534 [12] In the 1956 short story "The Dead Past" by Isaac Asimov, a historian is excited to use a time viewer to study ancient Carthage, only to find out that the device is limited to viewing the most recent 120 years,[5]: 127 and a historian uses a time viewer to read the contents of the Library of Alexandria in the 1980 short story "One Time in Alexandria" by Donald Franson.[13]: 283
An early instance of a time viewer being used to solve crimes is the 1926 novel The Vicarion by Gardner Hunting, as events leading up to a crime can be uncovered in reverse after the fact.[2]: 101–102 [3] Later examples include the 1948 short story "Private Eye" by Henry Kuttner and C. L. Moore (writing jointly as "Lewis Padgett"), which revolves around a man planning a murder in such a way that the use of a time viewer by the authorities would not reveal his guilt,[2]: 103–104 and the 2006 film Déjà Vu, where the device shows events with a four-day delay which cannot be adjusted and there is consequently only one opportunity to view any given event.[3][15]
Entertainment
The 1926 novel The Vicarion by Gardner Hunting is an early example of time viewers being used for entertainment;[3] in the story, moments from history are shown in movie theaters to great public interest. Baxter compares the in-story effects on society, where "mass addiction to this vibrant spectacle quickly overtakes the public", to the later real-world advent of the television.[2]: 101–102 This theme recurs in the 1947 novelette "E for Effort" by T. L. Sherred, though in that story the public is unaware that the films are not conventional movie productions.[5]: 127
Privacy and espionage
A number of works explore the implications of being capable of remotely viewing the recent past—potentially as recent as less than a second ago—on privacy.[2]: 101–102, 104–105 [3][5]: 127–128 [16]: 266 In the 1956 short story "The Dead Past" by Isaac Asimov, its use is suppressed by the government for this reason.[2]: 104–105 [5]: 127 In the 1972 fix-up novel Other Days, Other Eyes by Bob Shaw, particles of the slow glass that captures images are spread all over to enable mass surveillance.[3] The 1976 short story "I See You" by Damon Knight posits that the complete loss of privacy resulting from universal access to a time viewer would usher in a utopia free from deceit and embarrassment.[2]: 104 [3]
Espionage applications appeared early; in the 1926 short story "The Time Eliminator" by pseudonymous author "Kaw", the United States government uses a time viewer to spy on a meeting of foreign leaders.[2]: 101 [3] The realization that it can be put to this use triggers war to ensure that it does not in the 1947 novelette "E for Effort" by T. L. Sherred.[2]: 103 [3]
The implication that just as we are watching the past, people in the future are surely watching us is explored in the 1951 short story "Operation Peep" by John Wyndham. In order to regain privacy, people eventually resort to shining bright lights to effectively blind the future onlookers.[2]: 102 In the 1953 short story "The Parasite" by Arthur C. Clarke, the realization that he is constantly being watched by a future being eventually drives a man to suicide.[2]: 102 The intensity of observation from the future is measured in the 1981 short story "The Final Days" by David Langford to gauge an individual's importance to the world of the future.[3]
Altering the past
Several stories reveal that the time viewer can not only observe the past but influence it.[2]: 99 In the 1951 short story "The Biography Project" by H. L. Gold, being constantly watched drives Isaac Newton insane.[2]: 99 In the satirical 1948 short story "The Brooklyn Project" by William Tenn, the scientists in charge insist that the past is immutable even as they and their surroundings undergo drastic changes, because from their new perspective those alterations have always been in place.[2]: 99 [17]: 205 [18]
Future-viewing devices are occasionally limited in what they are able to show rather than being general-purpose.[3] One example is the device in the 1939 short story "Life-Line" by Robert A. Heinlein which can determine an individual's moment of death by measuring the reflection from the future end of that person's world line; a similar device that reveals the manner but not time of death appears in the 2010 anthology Machine of Death: A Collection of Stories About People Who Know How They Will Die by Ryan North, Matthew Bennardo, and David Malki.[3][5]: 128 Another is the instantaneous "Dirac communicator" introduced in the 1954 short story "Beep" by James Blish which due to the lack of a speed-of-light delay can send messages to the past.[3][25]: 148–150 [26]
^D'Ammassa, Don. "William Tenn". www.dondammassa.com. Retrieved 2022-07-29. "The Brooklyn Project" however is one of my favorite time travel stories. Despite warnings that changes wrought in the past would be undetectable because people in the present would assume they had always been the case, an experiment leads to the replacement of humanity by intelligent amoebas.