Time machine (device)

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A time machine is a fictional or hypothetical device that allows time travel.

Contents

Concept

A time machine is a device which brings about closed timelike curves—and thus enables time travel—where none would have existed otherwise.

Stanford Encyclopedia of Philosophy (2024) [1]

A time machine is a device that makes time travel possible. [1] [2] [3] : 137 

The Stanford Encyclopedia of Philosophy distinguishes between two different types of time machines: a science fiction variety that is not bound by the laws of physics and a hypothetical variety discussed in theoretical physics that relies on the creation of closed timelike curves (CTCs). [1] Paul J. Nahin distinguishes between "weak" time machines that exploit existing CTCs and "strong" time machines that are themselves responsible for the creation of the CTCs. [4] : xxxiii  [5] : 555 

Brave New Words: The Oxford Dictionary of Science Fiction and The Encyclopedia of Science Fiction distinguish between this and time slip, where the time travel occurs without technological aid. [6] [7] : 230 The Encyclopedia of Science Fiction additionally distinguishes the concept of an immobile time gate or portal [8] .

The Encyclopedia of Science Fiction lists a number of related concepts that allow for more limited interactions with other points in time, but not transportation: a time viewer allows for observation, while a time radio enables communication. [2]

In fiction

Time travel has appeared in fiction since at least the 1700s, but the first instance of a machine being used for the purpose was Edward Page Mitchell's 1881 short story "The Clock that Went Backward". [2] [3] : 137  [9] The term "time machine" itself was coined by H. G. Wells in the 1895 novel The Time Machine . [2] [3] : 137  Later in the history of science fiction, time machines have often been wearable. [2]

In physics

The first theoretical basis for a time machine based on our scientific understanding of the universe came in 1949, when Kurt Gödel demonstrated that CTCs are in principle consistent with Albert Einstein's theory of general relativity—although the so-called Gödel solution to the Einstein field equations requires a universe with properties different than ours (in particular, it would have to be rotating). Nahin comments that since travel along the CTCs in Gödel's scenario requires some form of accelerating force (as opposed to being a free-fall path, or geodesic) it is an example of a proper time machine, although since it does not create the CTCs but rather uses CTCs inherent in the structure of the universe it is only a time machine in the weaker sense. [4] : xxxiii–xxxiv  [5] : 18–19  [10] : 10  Several different theoretically possible—even if impracticable—time machine variants have been conceived of and described since. [11] : 149  One of these is the Tipler cylinder, first described as a source of CTCs by Frank J. Tipler in 1974. [4] : 38–40  [11] : 149  [12] : 140–141  Time machines that create CTCs by way of wormholes were described in theoretical research by Michael S. Morris, Kip Thorne, and Ulvi Yurtsever  [ Wikidata ] that was published in 1988. [1]

See also

References

  1. 1 2 3 4 Earman, John; Wüthrich, Christian; Manchak, JB (2024), "Time Machines", in Zalta, Edward N.; Nodelman, Uri (eds.), Stanford Encyclopedia of Philosophy (Summer 2024 ed.), Metaphysics Research Lab, Stanford University, retrieved 2025-03-06
  2. 1 2 3 4 5 Nicholls, Peter; Langford, David (2017). "Time Machine". In Clute, John; Langford, David; Sleight, Graham (eds.). The Encyclopedia of Science Fiction (4th ed.). Retrieved 2025-03-13.
  3. 1 2 3 Pilkington, Ace G. (2017). "Time Machine". Science Fiction and Futurism: Their Terms and Ideas. Critical Explorations in Science Fiction and Fantasy. Vol. 58. McFarland. pp. 137–139. ISBN   978-0-7864-9856-7.
  4. 1 2 3 Nahin, Paul J. (2016). Time Machine Tales: The Science Fiction Adventures and Philosophical Puzzles of Time Travel. Springer. ISBN   978-3-319-48864-6.
  5. 1 2 Nahin, Paul J. (1999) [1993]. Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction. Foreword by Kip S. Thorne (Second ed.). Springer. ISBN   978-0-387-98571-8.
  6. ↑ Prucher, Jeff (ed.). "Time Travel". Brave New Words: The Oxford Dictionary of Science Fiction . with an introduction by Gene Wolfe. p. 230. ISBN   978-0-19-530567-8.
  7. ↑ David, Langford; Clements, Jonathan (2018). "Timeslip". In Clute, John; Langford, David; Sleight, Graham (eds.). The Encyclopedia of Science Fiction (4th ed.). Retrieved 2025-03-06.
  8. ↑ Langford, David (2018). "Time Gate". In Clute, John; Langford, David; Sleight, Graham (eds.). The Encyclopedia of Science Fiction (4th ed.). Retrieved 2025-03-06.
  9. ↑ Edwards, Malcolm; Stableford, Brian; Langford, David (2024). "Time Travel". In Clute, John; Langford, David; Sleight, Graham (eds.). The Encyclopedia of Science Fiction (4th ed.). Retrieved 2025-03-13.
  10. ↑ Broderick, Damien (2019). The Time Machine Hypothesis: Extreme Science Meets Science Fiction. Science and Fiction. Springer. ISBN   978-3-030-16178-1.
  11. 1 2 Nahin, Paul J. (2014). "Time Travel: Fact or Fantasy?". Holy Sci-Fi!. Science and Fiction. Springer Science & Business Media. p. 149. doi:10.1007/978-1-4939-0618-5_7. ISBN   978-1-4939-0618-5.
  12. ↑ Webb, Stephen (2017). "Closed Timelike Curves". All the Wonder that Would Be: Exploring Past Notions of the Future. Science and Fiction. Springer. pp. 139–146. doi:10.1007/978-3-319-51759-9_5. ISBN   978-3-319-51759-9.
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