That meant that you could just tune in and see any event in history. Barbara:
Do you mean... a sort of... "Time television"? First Doctor:
Yes, that's exactly what this is.
A chronoscope or time viewer is a device that uses images that show past or future events like a television. They can sometimes also cause time travel. They are common in sci-fi, and often take different forms.
Some act like cameras recording past and future events and showing what an object would look like in a different time period. Others are more like TVs and show videos and visions of the past and future. Chronoscopes are often used as plot devices, as they can often reveal various details that are necessary for the plot.
Compare Magic Mirror
or Crystal Ball
, which may have the ability to show these events as well.
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Anime & Manga
- In a Superboy comic story (based on a script from the Superboy live-action TV series that wasn't, apparently) Superboy flies out into space in order to make a home movie to show his friend that the friend's father was a hero during the war. Superboy goes faster than light so he can film the light coming from Earth, which shows what happened in the past.
- Krona uses one to see the beginning of the universe (unknowingly altering it in the process) in the Green Lantern comics.
Films — Live-Action
- The scroll in Tim Burton's Alice in Wonderland that showed the history of Underland and then prophesied Alice's return and her slaying the Jabberwocky.
- In the Denzel Washington movie Déjà Vu, it's claimed that the "Snow White" technology is just an incredible complicated surveillance system. Turns out that its actually a chronoscope. And when pushed, it even works as a limited time machine.
- In Paycheck, the mysterious device employs the curvature of the universe and special lenses to look a short distance into the future, allowing the protagonist to build his escape plan before the beginning of the main action.
- The Dead Past by Isaac Asimov is centered around such a device.
- In a twist, the really important aspect turns out to be something that in practice isn't about looking into the past (or the future, which the device can't do): it can look at any place at any sufficiently recent time... which means there is no privacy, since there are no limitations on how *close* to the present it can look. The government knew about this before (it was their motivation for their draconian rules, the intent being to keep it out of most hands and (per their representative's statements) unused, but once the protagonists invented a cheap and simple way to duplicate the technology and spread it widely...
- of course, Asimov failed to notice that his Strawman Has a Point: the government's power was based on their monopoly on chronoscopy, they blatantly admitted that they had used it specifically to suppress competition, and all scientific research was strangled by the same bureaucracy as chronoscopy, most likely enforced through the same means. The protagonists did not destroy privacy by publishing their findings, merely the government's illusion of it.
- Asimov's idea is further explored by Arthur C. Clarke in The Light Of Other Days. The chronoscope, a machine to create and look through wormholes in this setting, immediately becomes public and the novel explores how society would change as a result of the complete lack of privacy and ability to know the real events that modern myths and religions are based on.
- The first half of Pastwatch: The Redemption of Christopher Columbus is all about this kind of device. Then they figure out how to do actual time travel...
- There are actually two such devices. The first one was of limited use and wasn't precise enough to show people (they were seen as fast-moving shadows), but it did allow the researchers to see architecture and the like. Later, a more focused device was created, allowing very detailed images and sound to be shown. Fashions of the past became all the rage throughout the recovering world. Researchers had to learn ancient languages in order to understand what the people on the screen were saying. One case even had a Poke in the Third Eye moment. When viewing the life of a long-dead tribal woman, the researcher is startled to hear a description of a dream she had about people from afar watching her. The researcher shows it to several colleagues, "rewinding" the event twice before continuing. The tribal woman continues that they watched her three times and even gives the correct number of researchers. The researchers are a little freaked out.
- Additionally, a character reveals the twist similar to Asimov's The Dead Past. While the government has told everyone that the machines can't see anything as recent as 100 years ago, in reality it can see as recently as 15 minutes ago.
- The Time Machine stories by Donald and Keith Monroe. The eponymous time machine had a viewing device that allows its users to see scenes of the future and past before traveling to them.
- On the Discworld, there are the Omni-scopes which have the power to do this, although true to form the wizards spend a great deal of time and effort trying to eliminate that capacity, treating it as a bug instead of a feature. It seems all they wanted was an expensive version of a webcam.
- Also from The Science of Discworld books, Hex is able to treat our entire universe as one of these. Fast fowarding, or rewinding to see specific spots in human history (our universe canonically exists in a snowglobe on a shelf in the Unseen University, a wobbly shelf).
- Such a device is invented in Noon: 22nd Century, but it can only look into the past. The pictures it shows... aren't pretty.
- In the science fiction novella E for Effort, a man invents a time viewer which can see any past occurrence. It doesn't have audio, so they employ lipreaders to find out exactly what people are saying. Initially they use it to make films about the past.
- The Fellowship of the Ring. The Mirror of Galadriel can show visions of the past and the future. Sam sees events that will occur in The Two Towers during his and Frodo's entry into Mordor, as well as events in the Shire after Saruman takes over. Frodo sees the fall of Númenor and the founding of Gondor, which occurred in the distant past.
- Robert A. Heinlein's short story "By His Bootstraps". The Time Gate can be used to look backward and forward in time as well as to travel to the time shown.
- The Pensieve from the Harry Potter novels, which records and plays back memories, is a version of this. (Powerful wizards like Voldemort can falsify memories, but other powerful wizards like Dumbledore can usually tell.)
- Mirrors that work like this are mentioned in Septimus Heap.
- In L. Ron Hubbard's Battlefield Earth, the heroes want to find out what happened to a planet they bombed a year earlier, and so teleport a probe a light year away from the target to effectively look into the past with a ridiculously powerful telescope. They're also somehow able to manipulate the images and zoom in on particular cities after the probe has returned and they're watching the recording.
- In Mission Earth, also by Hubbard, the Voltarian Confederation uses "time-sights" to peer into the future in order to avoid oncoming obstacles when aboard spaceships using time-based "Will-be Was" engines (don't even ask). A character later has the bright idea to make millions on the stock market by looking at tomorrow's figures and investing accordingly.
- Phillip K. Dick's short story, Paycheck, employs one of these as a centerpiece of the conflict.
- The Doctor Who episode "The Chase" (with the first Doctor William Hartnell, and only the third Dalek story ever) features a Time-Space Visualiser which can view any event in history.
- The Atavachron from Star Trek: The Original Series.
- In Star Trek: Enterprise, the time traveller Daniels uses a device like this, while he is congratulating Captain Archer for successfully fixing the time stream.
- The Twilight Zone episode "A Most Unusual Camera" has a camera that can see into the future.
- The Time Tunnel. In addition to sending items and living beings through time, the scientists controlling the eponymous device could also use it as a time viewer to see the past and the future.
- GURPS Ultra-tech describes the "timescanner". It has very limited abilities: it can only display things in a two-yard radius, it needs days to focus on the specified moment in time, and it is only available in soft sci-fi settings anyway. And until a portable version is invented, the timescanner machinery occupies an entire room.
- In The Golden Apple, Mother Hare gives Ulysses and Penelope a glimpse of a verdant valley turned into future wasteland, and presents them with a kaleidoscopic vision, projected in the form of woodcuts and lithographs, of the spectacular scientific achievements forthcoming in the twentieth century.
- The clouds on Skaia in Homestuck are natural versions of this.
- It's heavily implied that a device like this will show up in Girl Genius at some point... though so far we've only seen it from the "other side", as it were. At several points in the comic, strange "windows" suddenly appear hovering in mid-air, with doubles of some of the comic's characters standing on the other side, seemingly discussing what they're seeing as if they were watching events happening in their past.
- Wormholes in theory could be used as this, you could move one exit of a wormhole near to a strong gravitational field, like a black hole, the gravitational effect will cause time to go slower in said wormhole exit than in the other; then when moving the wormhole's exit away from the gravitational field it will retain the "time delay" and effectively become a window/portal to the past, the only caveat being that it cannot show anything before the wormhole's creation.