The argument goes that if Time Travel were possible, we'd know about it, because we'd always be running into people asking "What Year Is This?". But who says time travel has to be a physical thing? An infrequent but recurring trope is that of Intangible Time Travel, in which people travel through time only as observers — as spirits or projections, but not as physical beings.
Because of the nature of the transport, this tends to happen more through magical means than scientific ones, although both have been used over the years.
This particular method also avoids many issues with paradoxes, as an intangible observer unable to interact with the physical world cannot alter objects or events in the past.
Sometimes, this isn't time travel at all; the "traveler" is having a vision or visiting someone's memory. Other times, the line gets blurred. Functionally, there isn't really a difference.
- In Princess Tutu Rue is able to relive her early memories this way when Uzura turns the gears of the Story backward. It's as weird as it sounds.
- Chrono Crusade: The manga has Rosette taking a Journey to the Center of the Mind in Chrono's soul, allowing her to walk through his memories and see them first-hand.
- In Princess Resurrection Hiro traveled back in time as a spirit thanks to a Back to the Future car
- Mahou Sensei Negima!: Negi uses this to show Asuna, and accidentally all his other students (Nadoka used her book to see what they were talking about and ended up showing everyone else the visions), in order to show her what happened to his village and the reason he became a mage so that he could look for the Thousand Master. It was meant to show how them the kind of world they would end up in if they continued to help him as his contractors, and the very real possibility that any or all of them could end up killed (or some equal fate) by demons, or other mages, or what the hell ever else you could think of, the idea being that if he could scare them away they would be safe. And it does scare them... for all of about six seconds, until the realization of the things hes been through (his village being destroyed and the path hes been pushed into as such a young child, having to basically give up his childhood to find out the truth about himself and his family, and find a way to save the villagers who got turned to stone) makes them all so FURIOUS that they basically vow to be his personal army to help him.
- Future Diary had this when Murumuru showed Yuki the "true" behind Yuno´s secret ...killing her current timeline version in the past and proceeding to impersonating her. However, Yuki´s desire to save this alternative Yuno in this vision was strong enough to defy the trope and make the second world Yuno hear (or at least sense) him in some way and even (in a very sad scene) call him for help by writing with her blood in a wall, but all in vain...
- Mobile Suit Gundam Unicorn:
- In the finale, in what is probably the largest and most awesome Continuity Nod in the franchise, Full Frontal takes Banagher back in time, flashing past Amuro Ray stopping the Axis drop, the fall of A Baoa Qu, Amuro's battles with the Elmeth and the Big Zam, the original colony drop, the destruction of Laplace Station and more, all the while Encounters from the third Mobile Suit Gundam movie plays in the background. They eventually end up going beyond the Big Bang, with Frontal pointing out that no matter what humanity may achieve, the universe will invariably return to the void they're in right now... before a Divine Intervention from Char and Lalah undoes the whole thing. The "Holy Shit!" Quotient is strong with this one...
- In the novels, the two travel forwards in time, with Banagher catching a glimpse of the Turn A.
- In 52, Ralph Dibny is shown his wife's murder through magical means, but is unable to stop it from happening.
- In The Invisibles, the team use the Hand of Glory, a mystical artifact, to fold time down to a point. At that moment, they receive flashbacks and flashforwards of events in their lives and the lives of others. In each instance, they are literally invisible to the people around them. Time travel through psychic projection is pretty commonplace in the series. Compare the "retrieval" of Marquis De Sade and King Mob's adventures in The Roaring '20s.
- The Golden Age and Silver Age comics had instances where Superman went intangible whenever he time-traveled under his own power. Of course, this was only in some issues; the writers changed the rules whenever it was convenient. This eventually calcified into a hard rule of time travel in The Silver Age of Comic Books—travelers heading to a time they already existed in would be reduced to intangibility, but would remain solid and able to interact with others if there was no other copy of themselves around (the idea being that by making it impossible to physically be in two places at once, the universe was preventing paradoxes).
- Whatever Happened to the Man of Tomorrow? by Alan Moore, the last Silver Age Superman story, uses this to heartbreaking effect. The Legion of Superheroes comes to bid Superman farewell, and Supergirl, being a member, comes with them. The story takes place after Supergirl's death, and Supergirl wonders why she didn't turn intangible and asks Superman what she's like when she grows up. Superman tells her that "Supergirl is in the past", assures her that she grows up to be beautiful... and breaks down sobbing when they leave.
- The Books of Magic: Young Tim Hunter, a potentially very powerful human magician, gets taken back in time in this manner by The Phantom Stranger as part of his education on magic. Later, unusually, he physically travels into one possible future (which people generally tend to see as spirits rather than physical beings) with Mister E.
- In Locke & Key, the Timeshift key allows the user to visit the day set on the clock as an invisible observer. It seems to be more like an action replay, as users can't see other people who have visited the same point in time using the key, and presumably certain events in the narrative (!) would draw quite a crowd.
- Fantastic Four: In one Tear Jerker of an issue, a young boy douses himself with fuel and sets himself on fire because he wants to be like the Human Torch. It doesn't help that an adult friend of his warns him to stay away from the fuel, jokingly saying that "it could turn you into another Human Torch". Johnny Storm himself is wracked with guilt over the incident, and then the Beyonder appears out of nowhere, intrigued by his grief. He takes them both back in time in intangible form to show Johnny how much the boy adored him. It doesn't help much.
- Savage introduced the Thousand Year Stare, a technique developed by Volgan scientists in collaboration with Ro-Busters that forces its victims to view millennia over the course of three days. This is used to develop war robots based on the ABC Warriors they see in the future - robots which will eventually develop into those same ABC Warriors.
- Constantine: John Constantine goes back in time and sees several scenes from earlier on in the movie, but remains intangible and invisible.
- Click: The rewind button on the main character's remote allows him to intangibly review earlier parts of his life.
- Déjà Vu: The movie's first half has the characters observing the events of several days earlier through a giant monitor in real-time.
- In Scrooged (as a take off on A Christmas Carol) the characters sees his past and is told it's "like a rerun" and they can't be seen or heard. Too bad because he tries to tell his past self to pick up on the fact that the office slut wants him and to not make the mistakes that caused his girlfriend to leave him.
- In It's a Wonderful Life, after the Senior Angel assigns Clarence to go to Earth and talk George Bailey out of committing suicide, the two travel to various key moments in George's life so Clarence can observe what kind of man he is and how he has come to be in his current situation. For all intents and purposes, they appear to be literally watching the movie along with the viewers at home, MST3K-style, and the Senior Angel can even pause the "footage" to explain certain events in more detail.
- The Ghost Goes West: Murdoch Glourie ghosts around for 200 years into the future (1935 being the future for him, and the present for the other characters), because he has some Unfinished Business.
- In A Christmas Carol and its many adaptations, Ebeneezer Scrooge is usually taken through time to see the errors he has committed in the past, how it affects those in the present, and how they will leave him unmourned in the future. Scrooge is completely invisible, inaudible, and intangible through these scenes to anyone in the time period itself.
- Kind of winked at during "Mr. Magoo's Christmas Carol". When Scrooge and the Ghost of Christmas Present are at the Cratchit house, the Ghost actually opens the door for Bob and Tim, who are coming home from church, and no one mentions or even notices.
- Winked at again in Arthur's send-up of the story. Prunella is in the role of "Scrooge." Her ghostly guide tells her that she can't be seen or heard by anybody while in the past. She's then bonked in the head by a rogue soccer-ball.
- Jacen Solo has this ability, called "flow-walking", in the Star Wars Legends books, in a universe which only rarely features "regular" time travel.
- Pastwatch: The Redemption of Christopher Columbus: At first, a machine called the Tempoview allows researchers to view and record history, supposedly unnoticed. (Turns out this isn't the case, and the technology is developed to allow standard Time Travel.)
- "The Men Who Murdered Muhammed", by Alfred Bester, has a very confusing variant on this. Time travelers can interact normally with the past or future... at first. However, if they cause a Time Paradox, then the universe responds by erasing them from existence. From the time traveler's perspective, they don't literally cease existing — rather, everyone around them spontaneously stops acknowledging their presence (except for other time travelers who've been similarly erased).
- A Handful of Time: An old pocketwatch allows Patricia Potter to observe her mother's unhappy past — from when her mother was her age and lived in the same house Patricia is staying.
- Odd Thomas: The titular character has come to the hypothesis that the insubstantial wraiths that gather when some really bad shit is going to go down are actually dicks from the future who enjoy watching human suffering. They aren't totally intangible, though, as upon knowing your knowing about them, they will rectify the situation by making sure you are no longer around to know.
- Peter F. Hamilton's short story If At First... takes Einstein's theory of not moving one single atom back. Somebody moves his mind back to his childhood years, overwriting the previous personality, and using his knowledge of future events, alters time. One guy uses it to advance the technological level of society, and the other guy uses it to become a rock star, plagiarizing songs not written yet.
- The novel The Light of Other Days, by Arthur C. Clarke and Stephen Baxter, is about the invention of a kind of wormhole technology that allows it's user to view any location, in real-time. Due to it being relatively easy to replicate, the technology soon gets out of the hands of the government and is available to the general public, which immediately has drastic social consequences (since, essentially, the concept of "privacy" no longer has any meaning). Then, it's discovered that the wormholes can also be projected into the past...
- Harry Potter has both "real" time travel, in which Never the Selves Shall Meet (Usually because one self will freak out and kill the other), but it also has Pensieves, which allow characters to jump into others' memories and remain intangible.
- That said, the reason was explicitly that the past self would attack the future self, assuming not without reason that it is a doppelganger of some sort, mostly because the reverse makes no sense. But it is never said that you couldn't carefully set up some stable time loops to exploit time travel. The series does not, nor indeed bring it up again after the one time, but several fanfics have run with the idea.
- The basis of the short story "Nostolgianauts", in which people start freaking out at the "ghosts" appearing everywhere till they realize that they're tourists from the future. People start wondering when this technology will actually be invented, and the main character gets to witness her nerdy best friend's wealthy, future self coming back to gloat at the bullies who were picking on him in school.
- Used in Going Postal when Moist sees the past of the Post Office. However, he's still moving around in the present. The place had fallen apart quite a bit between the two time periods, as two of his deceased predecessors found out when one stepped onto a balcony that wasn't there anymore, and one fell down a flight of stairs that wasn't there in the past.
- Used as the "inspiration for the story" in Last and First Men, as shown by the introduction to the book.
- Isaac Asimov wrote a number of short stories that involved this concept, most notably "The Dead Past", where it turns out that the government has been suppressing chronoscope technology because the ability to look at the recent past anywhere in the world would completely destroy the idea of privacy.
- Another one features a company that traces genealogy using their device, usually telling customers that they're related to someone famous. The inventor goes crazy when he realizes that he is the first person in his family, back to the beginning of the human race, who has ever done anything of note.
- In the book JumpMan, the titular time-travel devices can only travel to certain points in history and leave their users a tiny bit out of sync with their timelines, leaving them invisible and (from what I recall) intangible, in accordance with the First Rule of Time Travel ("Don't Touch Anything"). The plot arises when a contest winner is accidentally given an illegal prototype JumpMan which DOESN'T do this...
- Rock of Warrior Cats can travel through time like this. And he can also interact with time travelers.
- In Incarnations of Immortality, this happens if one time travels to a time period where they never existed.
- Dinoverse seems to set this up, as traveling characters become invisible beings of 'pure thought-energy brainwaves', but they're never like this for long - said characters end up possessing the bodies of dinosaurs, acting through them.
- Daphne du Maurier's novel House on the Strand, which involves several travels from 20th century Cornwall to its counterpart version during The High Middle Ages.
- In How to Live Safely in a Science Fictional Universe, the physics of the universe prevents you from going back to an event you weren't at and changing that event by throwing you into another timeline. A heartbreaking example is of a young woman who uses time travel to get back to the moment when her grandmother died, because she wasn't there the first time. The grandmother can neither see nor hear her; even though they're in the same room, they're actually separated by a universe.
- Fans of sci-fi and/or The Inklings have been looking for a long time for the Time Travel story C. S. Lewis alluded to in the prologue to The Great Divorce (1945), wherein a guy goes into the past, but its immutability means he cannot even eat a sandwich, or keep a raindrop from piercing him clear through.
A likely candidate is the unfinished Lost Road by J. R. R. Tolkien, which he began and abandoned in the late 1930s, re-started as The Notion Club Papers in 1945, and abandoned in 1946 so the author could finish something or other about hobbits. As the story originated from an agreement between Tolkien and Lewis to write companion space-travel and time-travel stories, and JRRT had read bits of his to Lewis, the latter started referring to them in print on the assumption they'd soon be published... What exists of both stories is already as "published" as they're going to get, in The History of Middle-earth vols. V and IX.
Both stories involve a father-son pair in England who experience repeated intangible Time-Travel dreams/visions, taking them back to past father-son pairs with the same names, who experience the same dreams/visions, recursively going back until reaching the original pair in Númenor, and witnessing the destruction of the Atlantean island kingdom. It was going to involve around half-dozen pairs of Englishmen witnessing mythical events or seeing from others' points of view, and much speaking in tongues.
- In Elizabeth C. Mock's The Children of Man series, this is known as "stepping" and is one of the abilities granted by purple magic.
- At one point, the hero tries to use his magic to save the Love Interest's baby boy while in the past. The backlash nearly kills him, and ends up briefly stripping his magic of its colors, causing him to transform into one of the bizarre colorless mages known as Grays.
- The Star Trek EU trilogy The Q Continuum has Q take Picard on a trip through Q's past to show him why he has to abort his current mission. Throughout the trip they remain in "observer mode".
- The Well of Moments is a simple 5th-century stone pot with runes around the rim—except looking into it will show the viewer snippets of the past, their own or someone else's, as if they're really there reliving the experience. Its ringed "lid" is called the Eye of Sorrows, which looks to the future. Putting them together is a very bad idea.
- In Quantum Leap, Al is able to project himself into the past, but he is visible only to Sam and a selected few other characters (e.g. young children, animals, mentally ill). Sam has to do the hard physical work of putting right what once went wrong, and has to partially take the bodyspace of someone already in that time, he can't just appear via a portal.
- In Torchwood a device exists that allows someone to be intangibly transported into scenes of strong emotion from the past. When put together with another identical device, it allows the same thing to happen with the future.
- In Heroes, Peter sort of does this, but not intentionally as he couldn't control his abilities. He travels back in time but turns invisible, only one character knows he's there and his past self isn't aware of him.
- In the Supernatural episode "All Hell Breaks Loose, Part One" (S02, Ep21), the Yellow-Eyed Demon takes Sam back to see what happened on the night of Sam's 6 month birthday in a dream where no one can hear or see them.
- Game of Thrones: During Bran's visions of the past with (and later without) the Three-Eyed Raven, he experiences events this way: he feels as if he were physically present, but other than the Raven, no one else takes notice.
- Daniel Amos's ¡Alarma! has a story in the liner notes where the narrator is transported via a dream into a city and finds he's completely invisible, inaudible, and intangible to everyone there. Which proves frustrating, as the narrator is also the Only Sane Man, and he wants to scream at everyone to stop being such fools.
- The time travel based RTS game Achron has this in the gameplay. The player is able to freely look at any point on the timeline, but if the time you are looking at is too far in the past you will be unable to make any changes to it.
- In Tomb Raider: Anniversary, a few cutscenes show Lara doing this through a magical artifact. Since TRA was a remake of TR 1, it was probably in there, too.
- This is essentially what Ellone does to Squall and company in Final Fantasy VIII, although they're dropped within other people's bodies (which they can't control, but can get the attention of). A powerful enough sorceress can apparently override the "can't control the person you're inhabiting" restriction.
- The final dungeon of Devil Summoner: Raidou Kuzunoha vs. the Soulless Army has the eponymous protagonist literally traveling through time, climbing his way through a dungeon where every floor represents a later decade. Many of the NPCs in this location are ghosts from their respective time periods, but a few are Intangible Time Travelers, and they comment on how dangerous it is to wander through time in corporeal form like Raidou is doing. The villain actually happens to be such a time traveler, having possessed a girl from Raidou's time period in order to change the past so that the events of the original Shin Megami Tensei 1 and 2—which some of the aforementioned ghosts are a Shout-Out to — never happened. More surprisingly, said villain turns out to be Raidou's successor from an unknown number of generations hence.
- Max gains the "future vision" ability in Sam & Max Season Three.
- Played with in Kingdom Hearts 3D: Dream Drop Distance. According to the rules of time travel, to successfully do so, the user must leave their body behind, there must be a version of oneself at the intended destination, and one cannot change the events that are meant to happen. By exploiting these rules, Master Xehanort's Evil Plan has been put in place.
- This happens in the Assassin's Creed franchise by using the Animus to relive the protagonist's ancestors' memories. This is also played with as Those Who Came Before were counting on this and used it to led the protagonist to sacrifice himself to save the planet from a devastating solar eruption.
- Zig-zagged in Ghost Trick: Phantom Detective. One of the protagonist's ghost tricks is to travel back in time, to four minutes before a person's death. Despite being a ghost, he averts this trope; he can still interact with the world through the objects he possesses. However, other ghosts that don't have ghost tricks can tag along with him; they play this trope straight by only being able to speak with the protagonist.
- Used once in Bob and George. Dr. Light makes a time traveling suit of armor that can make the wearer intangible to prevent unnecessary changes to the timeline. It works great, right up until the armor breaks.
- Spes Phthisica uses the 'true-visions of the future' version.
- According to Einstein, this is how real time travel would have to work. He theorized that it could be possible to travel through time, as long as you didn't disturb even a single atom on the way, meaning you would have to be intangible and invisible.
Unfortunately, that also means none of your senses work, since all of them operate via the interaction of molecules: no light particles strike your retinas, no sound waves jiggle your ear drums, no flavors reach your taste buds, no odors waft up your nostrils, and nothing on your skin or in your body could react to the surrounding environment. Also, depending on how space-time is actually connected, your own personal time may also have to be frozen in order to obey the "no disturbance" rule (so you don't, say, asphyxiate shortly after you arrive in the past and fuck things up that way).
Thus, the trope would be inverted: you could be there, but you'd be able to experience or witness precisely nil.