The bootstrap paradox, or ontological paradox, is a paradox of time travel in which information or objects can exist without having been created. After information or an object is sent back in time, it is recovered in the present and becomes the very object or information that was initially brought back in time in the first place. Numerous science fiction stories are based on this paradox, which has also been the subject of serious physics articles.
The term "bootstrap paradox" refers to the expression "pulling yourself up by your bootstraps"; the use of the term for the time-travel paradox was popularized by Robert A. Heinlein's story By His Bootstraps.
The term "bootstrap paradox" refers to the expression "pulling yourself up by your bootstraps"; the use of the term for the time-travel paradox was popularized by Robert A. Heinlein's story By His Bootstraps.
- A professor travels forward in time, and reads in a physics journal about a new equation that was recently derived. The professor travels back a few seconds after the journey was made, and relates it to one of the students who writes it up, and the article is published in the same journal which the professor reads in the future.
- A person builds a time machine. This person goes into the future and steals a valuable gadget. This person then returns and reveals the gadget to the world, claiming it as their own. Eventually, a copy of the device ends up being the item the person originally steals. In other words, the device is a copy of itself and it is not possible to state where the original idea for the device came from.
- A young physicist receives an old, disintegrating notebook containing information about future events sent by this person's future self via a time machine; before the book deteriorates so badly as to be unusable, the person copies the information in it into a new notebook. Over the years the predictions of the notebook come true, allowing this person to become wealthy enough to fund their own research, which results in the development of a time machine, which is used to send the now old, tattered, disintegrating notebook back to the former self. The notebook is not a paradox (it has an end and a beginning; the beginning where it is received and the end where it is disposed of after the information is copied out), but the information is: It's impossible to state where it came from. The professor has transferred the information that was written out by oneself, so there was no original information.