Provoked by a comment by Steve Mangiameli.

In my short story series, Penniless Joe is a down on his luck archaeologist/(al?)chemist that is struggling to get employment.

One day he goes to a pawn shop sell some stuff. The pawn shop owner convinces him to buy some weird liquor bottle he found. Joe is intrigued by the ceramic vial, with some uncommon characters he barely recognizes. He buys it for $1.99 and takes it home to decipher it.

He finds out that it is a "Groundhog day potion" that supposedly allows one to re-live one single day.

Joe decides to use the potion to get out of his wealth predicament. His choice is to win the state lottery.

Unknown to him, he made a mistake translating the inscriptions on the potion, and become a permanent "groundhogger".

The rules so far are:

  • A groundhogger re-lives each day from 3 to 5 times before moving on to the next day. The amount of repetitions is random and cannot be predicted.
    • A "repeat day" is day that will be erased and repeated. Days 1 and 2 of a cycle are always a "repeat day", day 3 is a repeat day ~33% of the time, and so on.
    • The "last day" or "real day" is the day where "tomorrow" is "calendar tomorrow".
  • If a groundhogger stays awake until midnight of a repeat day, everything goes black exactly at midnight, and the day begins anew at his first conscious moment of that day.
  • If a groundhogger stays awake until midnight of a last day, he does not black out, and tomorrow's repeat days begin exactly at midnight.
  • Anything that happens on a repeat day has no permanent effect. He just wakes up again next(this) morning. Just like Bill Murray's, even death is not permanent. He just awakes again this morning (to his subjective perception, immediately after losing consciousness and dying).
    • That includes internal body changes, like catching a disease or impregnation (for a female groundhogger).
    • Physical fatigue/wounds are completely erased. Mental fatigue is relieved completely if he wakes up from sleep. but only partially if he stays awake overnight. For that reason, they prefer to sleep.
    • Since days 1 and 2 are always repeat, they are more daring on these days.
  • He probably becomes permanently dead if he dies on a "last day". But he did not try that so it is unknown.
  • He is not bound to a specific location. So he can travel to Vegas on a "last day" and wake up in Vegas tomorrow.
  • He retains full knowledge/memories of what happened in the repeat days, to the limit of his own cognitive capabilities. No physical objects (paper notes, files on a USB drive, etc) are retained or changed on a repeat day.

Later on he finds other groundhoggers. It is dead easy to spot one when you meet him, because it is the only thing that changes on repeat days.

So on the interaction between groundhoggers:

  • Both groundhoggers freely and independently retain memories of repeat days.
  • Both of them can act on their own free will and do whatever they want on repeat days. Even avoid/escape meeting the other guy again.
  • If a groundhogger is killed by another groundhogger on a repeat daynote1, the dead one awakes next morning (to his subjective perception, immediately).
  • If a groundhogger kills another one in a last day, the effect is unknown. Probably permanent, but nobody tried.
  • There is no compulsion over groundhoggers (no, there can be more than one) to act or interact with each other. There may be curiosity or kinship, but most avoid each other out of fear.
  • Even on repeat days, the actions of one groundhogger can cause changes on the environment of another (thus causing the repeat days not to be equal). This (things not happening exactly the same way) is usually the tip to the presence of another groundhogger.
  • It is unknown if all of them experience the same amount of repeat days for each day.

Given the rules above that already fleshed out on the written stories (and considered canon), what is the best explanation to how it works? I thought of some:

  • Physical Time travel: groundhoggers do travel back in time. This does not explain how their bodies are repaired/recovered.
  • Subjective space/precognition: they aren't actually repeating the days. They gain a very precise precognition ability, and are only mentally re-living that in their minds. This does little to explain how groundhoggers can interact with each other independently.
  • Mental Time travel: groundhoggers send their consciousness back in time. This has the problem of explaining how their consciounsness are replaced.
  • Alternate dimensions: each repeat day happens in an alternate dimension. This burns even more handwavium than the first one, above.

The list above is not meant to be exhaustive. Other explanations might exist.

So, what explanation to the effect described above requires the least handwaving, what its pros and cons, and where does it fall short?

  1. They know days 1 and 2 are always repeat. So they can be rather daring and open to experiments on these days.
  • $\begingroup$ Are you feeling very strongly regarding the potion aspect? What if it's a more meta-physical explanation and the groundhogger has a little more control of the day(s) to be relived? You could do this with a talisman or device (alien?) that has the ability to anchor consciousness to a particular space/time plane, lasting 24 hours before reset. Whether you do this with the potion or device, I'm having trouble reconciling the rule regarding location - how does everything else reset except for the location? $\endgroup$ May 25, 2016 at 18:54
  • $\begingroup$ The talisman option could add to the story and why there is an organization hunting down groundhoggers, collecting the finite number of available (not able to be duplicated/synthesized) devices in order to shape history as they see fit or some other such end. $\endgroup$ May 25, 2016 at 18:57
  • $\begingroup$ @Steve: I believe that the OP is saying that location isn't an exception — on a "repeat day", everything resets (including location); on a "last day", nothing resets (not even location). $\endgroup$ May 26, 2016 at 1:21
  • $\begingroup$ Why not just have the main character be insane. $\endgroup$ Jun 22, 2016 at 19:42

4 Answers 4


Since travelling back in time, swapping consciousness, etc. are all pretty "magical" explanations and you're looking for some realism, I'd like to propose an unpleasant possibility:

These groundhoggers are not human beings with amazing capabilities. Instead, they are aspects of a Virtual Reality which are bugging out.

Terminally Ill

Joe is a terminally ill patient hooked up to a Virtual Reality machine - his body is broken beyond repair, but his family is paying for him to live out his days in a fantastical VM universe where he can enjoy his last few days.

The scenario for which they paid is one in which Joe gets to use his business knowledge to manipulate the world in a setting where the day repeats, but he's the only one who realizes it - they know it would be a fun challenge for him!

Economic Sim

This was actually the subject of a sci-fi book from the 80's which I read about a decade ago:

An accident at a nearby chemical plant releases a toxin into a small town which puts all of the inhabitants in a coma - they will soon die. The government seizes the opportunity! They go in and copy each person's consciousness, then makes a miniature reproduction of their city, and tiny robots that look like the people, etc. (ridiculous, I know), then uploads their memories, and use that setup to run social experiments on them. They reset the robots at the end of each experiment, but one day they miss one. He begins to relive the same day over and over again, with no explanation of what the heck is going on. He also witnesses the others being reset, etc.

You could explain your story in a similar sense, but in a virtual world, not using tiny robots. Joe is an uploaded consciousness, or even an AI which is bugging out, and thinks the VM is real. He is not being properly reset when the VM reloads.

  • $\begingroup$ The VR option reminds me too much of Vanilla Sky... I really like (and it surprised me) the lateral thinking you showed us. Thanks for your feedback. $\endgroup$ May 25, 2016 at 19:19

You're not going back in time, you're going forward

Scientifically, it's hard to argue you can go back in time and everything resets (except your memory). It's a lot easier to suggest your mind explores the day before it actually happens (and that it can do so a couple of times before the actual day).

So let's say some scientific phenomenon says that there's a kind of pseudo-quark potential energy (PQSE) that radiates off all matter in anticipation of how it will act and interact with the rest of the universe.

When groundhoggers sleep their consciousness begins to read this PQSE and experience living in the day that hasn't happened yet. Time, the length of their "day", the mental state of the groundhogger etc. could determine how many times they can repeat before the actual day dawns and they wake up, this time to actually live the day.

Since all groundhoggers tap into the same PQSE, their actions effect what each other see, so they can interact with each other.

To the groundhogger, the real days wouldn't seem much different to the PQSE day, the only difference is that the changes of this day carry on into the future days.


The best explanation, I think, would be to give no explanation at all. You are making up a set of rules about time travel that does not work in reality and as you said, any explanation would be a hand wave. Just having the potion work with no explanation to its origins is a valid strategy. This is what the groundhog day movie did - they used to have scenes showing that the looping was caused by a curse by the main characters' ex-girlfriend, but the movie worked better with those scenes removed.

That said, if you do want to have an explanation here is my ideas. Two thing you wrote stick out to me. One are some of the rules: the reset is always at midnight, and the number of repeats of each day number from 2-4 with an even distribution. This sounds like rules that are purposefully designed by a human to be useful and intuitive but not too exploitable, and not what you'd do if you wanted to use the potion yourself if you could help it. The other is that you mentioned that Joe is an alchemist, meaning there is already magic in the setting (or at least alchemy). The most believable explanation is the one that requires the fewest new assumptions, so the explanation would preferably be magical as well.

Looping explanation: the potion loosens the grip your soul has on your body, making it detach and attach again at certain times. Your soul holds your memories, but you body is what grounds you in reality - including time. When you've experienced a repeat day, your soul is pulled back and merges with the previous version of you, giving him the memories. This functions even if you died, since the soul still hangs around after death.

Potion explanation (less necessary to include, but the reason for its existence): A whole bunch of these was made by a powerful wizard/alchemist/genie/god/other that wanted entertainment. Such a potion is complicated and expensive to make, but he/she/it made and distributed several all over the world to be sold cheap to observe what fun things those who drank it would get up to and interact with each other - while being able to observe everything from some cosy pocket dimension or other space outside of time.


The problem with a potion is it is ingested and wears off in time as the body metabolizes the potion. The strength of the potion and the speed of an individual's metabolism would effect the duration differently, dose to dose and person to person. But eventually it would stop working. You see this in many other story lines and makes a lot of sense. As such, your protagonist would need to constantly be ingesting the potion with no way of knowing how long it will last, but somewhere between 3 - 5 days.

The potion doesn't turn back time, per se, but causes the user's consciousness to "anchor" to a point in time. When the consciousness gets 24 hours out from the anchor, the user is yanked back to the anchor point. It is only when the potion wears off that the anchor is released and the consciousness is allowed to continue down the linear path of time and space as we know it.

This mechanic allows for a little more reality in that it isn't a "forever" effect and can be controlled, to a point, by the user. Additionally, the user is bound by the 24 hour rule for 3 - 5 days, but not by an arbitrary, already done, midnight. This would give the user a great deal more flexibility in the usage of the potion.

Taking the potion allows the user, known as a Groundhogger, to learn "quicker", be extremely "lucky", and the "ability" to predict future events. These are the tell tale signs other Groundhoggers use to spot each other, of which, there are few others.

Joe, a brilliant, young chemist, has trouble holding a job due to his intellect and intuition when it comes to chemical bonding. His superiors are threatened and his peers think he's just weird. Joe happened on the potion at a science expo, perusing the latest advancements. He runs into a frightened, desperate man who identifies, begging for help from unknown pursuers. Before Joe can respond, the man bolts off again, leaving behind several vials of potion in Joe's coat pocket. Joe finds these later and reverse engineers them - finding all of the ingredients odd, but safe for consumption.

The potion isn't really a potion, but rather a by-product of time travel research. The researchers aren't part of any government agency and their exact existence and purpose are a mystery. Suffice it to say, there is a lot of power and wealth that comes with the ability to know the future, even if it is only 24 hours out. This agency will stop at nothing to protect their research and get back what was taken.

Some unknowns at this point that may need to be fleshed out and could come in handy as plot twists or guides:

  • How exotic are the ingredients? While known and consumable, maybe one or two are difficult to come by
  • Does the Groundhogger continue to age while looping? A 30 year old that looks 60 could be another "indicator" of a Groundhogger. Of course a billionaire 20 something with the wisdom of a century could be as well. Just depends on whether or not they age normally
  • Are there any after effects of the taking the potion? Beside possible aging effects, does taking the potion constrict blood vessels or put undue stress on the heart, or over time cause consciousness hold in time/space to be lost

Lots of questions! But this sounds like a really fun project. Best of luck!

  • $\begingroup$ Welcome to the site Steve. If you have questions on the site check out the help center and feel free to visit us in Worldbuilding Chat $\endgroup$
    – James
    May 26, 2016 at 14:06

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