Wormhole

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An illustration of a wormhole in a two-dimensional universe. Both a path along the red and one along the green arrow is a straight line in blue, two-dimensional space .

Wormholes are theoretical structures that result from special solutions ( Kruskal solutions ) of the field equations of general relativity . They were first described in 1935 by Albert Einstein and Nathan Rosen and therefore originally called the Einstein-Rosen Bridge .

The English term wormhole was coined in 1957 by John Archibald Wheeler . The name wormhole comes from the analogy with a worm eating its way through an apple. It connects two sides of the same room (the surface) through a tunnel. This clearly describes the special property of the Kruskal solutions, as they connect two places in the universe with each other.

Theoretical basis

Simulation of a view into a wormhole that connects the paved square in front of a high-rise building in Tübingen with a dune landscape on the English Channel

The general theory of relativity extends the clear Euclidean space of everyday experience to the more general structure of spacetime . Mathematically speaking, spacetime is a four-dimensional, pseudo-Riemannian manifold . Any form of energy, such as mass, light or electrical charge, causes changes in the geometric properties of space-time, which in turn have an influence on the movement of objects in the area. This influence is gravitation and one generally speaks of a curvature of space-time. At this point it should be noted that it is a common mistake to only speak of a curvature of space, since time is also distorted, which results in effects such as gravitational time dilation .

The gravitational field of a specific energy distribution is a solution to the Einstein equations . The best known and simplest is the Schwarzschild solution , which describes the gravitational field of a homogeneous, non-charged and non-rotating sphere. It thus describes, to a good approximation, the gravitational field of the earth or a star in the outer space. If, on the other hand, a star collapses into a black hole , the Schwarzschild coordinates are insufficient to describe the entire structure. At the event horizon of the object there is a coordinate singularity beyond which the Schwarzschild coordinates do not extend. However, it is not a physical singularity, as it can be corrected by choosing new coordinates. This happens with the help of the Kruskal-Szekeres coordinates , which also describe the space-time in the interior of the event horizon. It turns out that in addition to the exterior and interior of the black hole, there are also equivalent, mirrored spaces. Thus, a possible transition to a white hole emerges, from which matter may emerge, but into which it cannot penetrate.

The connection between the two gravitational anomalies is referred to as the Einstein-Rosen bridge and the entire object as a wormhole , especially when a black hole and a white hole are connected as a Schwarzschild wormhole, which can only be crossed in one direction. In principle, it is conceivable that wormholes connect two places of the same spacetime or two different spacetime of a multiverse .

Models

So far, there is no experimental evidence for wormholes. In 1962, Wheeler and Fuller showed that wormholes in general relativity are unstable. Some scientists like Kip Thorne come to the conclusion that an instability of the wormhole connection can only be prevented by so-called exotic matter . Assuming their existence, he constructed models of wormholes that could be traversed in both directions (Morris-Thorne wormhole 1988).

Stephen Hawking did not completely rule out that falling particles of normal matter could nevertheless cause the wormhole to collapse quickly. In his book The Universe in a Nutshell , Hawking gave a lot of thought to the practical implications of utilizing wormholes.

The exotic matter has the property of having an anti-gravitational effect in a certain area of ​​space (where the wormhole is supposed to be) (more precisely, it has a negative mean energy density ). So far there is no known way how to make exotic matter, let alone how to use it to build wormholes. Some estimates suggest that a wormhole one meter in diameter would require exotic matter equivalent to the mass of Jupiter . It is possible that only microscopic wormholes (that is, the size of a few atomic radii ) are possible if exotic matter or negative energy densities are involved. Matt Visser of Victoria University ( Wellington ) assumes, however, that even very small amounts of exotic matter are sufficient to create wormholes. Visser also speculated that variants of cosmic strings may have created wormholes in the early days of the universe that could be observed today through the gravitational lensing effect .

Theoretically, it would be possible to turn a passable wormhole into a time machine by accelerating one end to relativistic speeds, similar to the twin paradox . The discussion about which protective mechanisms (possibly including quantum theory) prevent this here and in other cases (Chronology Protection Hypothesis) is described, for example, in the book by Kip Thorne Black holes and time warps .

In 2016, Ping Gao, Daniel Louis Jafferis and Aron C. Wall found a new type of wormhole that can be traversed in principle and that does without exotic matter of negative energy density. They built on the ER-EPR conjecture by Juan Maldacena and Leonard Susskind , which postulated the equivalence of special wormholes and pairs of quantum entangled particles (EPR pairs) and used them to solve the information paradox of black holes and its intensification in the fire wall. Paradox was used by Joseph Polchinski (in addition, the authors saw a new image of quantum gravity or a stable quantized space-time, the existence of which is ultimately due to quantum entanglement). Dao, Jafferis and Wall found that their scenario is mathematically equivalent to a description of quantum teleportation , which has also been reinterpreted. The information that has disappeared in the black hole reappears at the second black hole, which is causally connected to the first via the wormhole (both are quantum entangled and the information has therefore not disappeared). However, the entanglements do not build up, as in the Feuerwall paradox, since the information in the second hole first has to get back to the first via the usual spacetime. The firewall paradox, which is based on the fact that only two particles can be entangled according to quantum mechanics, but in the case of black holes there are many particles in Hawking radiation, was previously used by Polchinski as an argument against the existence of black interiors Holes have been used. As with quantum teleportation, there can be no time travel over the wormholes. The new interpretation is also an argument for the idea of complementarity between the inside and outside of black holes (Black Hole Complementarity), a solution to the information paradox of black holes proposed by Leonard Susskind and Gerard 't Hooft .

Science fiction

Science fiction that wants to move within the framework of science likes to use wormholes to speed up travel in space. The Deep Space Nine series from the Star Trek series, for example, is about a remote space station that is of great strategic and economic importance due to a wormhole discovered nearby. However, this wormhole is not actually a wormhole, but an artificially created passage. The Stargate series, which has been running for several years, also uses this technology. In the movie Donnie Darko , on the other hand, the existence of a wormhole is used as the starting point for a paradoxical and ambiguous story about time travel, fate and metaphysics. Here, too, the frame of the story is only apparently of a scientific nature and is prepared with numerous elements of fantasy . Furthermore, in the film Déjà Vu - Race against Time, there is a machine that can look into the past through wormholes, smuggle small amounts of matter into the past and even change the past. In the film Contact , an artificially created wormhole is used to contact another civilization. In the Sliders series it is possible to travel to parallel worlds via wormhole. In the comic book version Thor , the gods travel to connected planets also through a wormhole. In the film The One, the main character travels through wormholes to kill his doppelgangers from all other universes. Another reference to wormholes is the main component of the gameplay of Portal , in which the player creates wormhole-like passages through two portals using a device in order to avoid obstacles and solve puzzles. In the third part of the Crysis trilogy , the theory of wormholes is also used.

This representation of wormholes in science fiction has little in common with the theory described above. For example, the wormhole is often depicted as a two-dimensional "hole" that people enter and exit. However, according to wormhole theory, the opening of a wormhole is spherical. Most science fiction writers also ignore the enormous tidal forces predicted by the theory . From a scientific point of view, such fantasies are therefore unrealistic. Representations of wormholes, which correspond more to the current state of knowledge, can be found in The Light of Distant Days by Stephen Baxter and Arthur C. Clarke and - in great detail - both in the books Diaspora by Greg Egan and Contact by Carl Sagan and in the construction of the world - Orion's Arm Internet project .

The science fiction film Interstellar , which was released in 2014 and was made with the advice of the scientist Kip Thorne , also uses the subject of wormholes. In this film, the wormhole, as the theories describe it, is represented as a spherical structure.

literature

  • Stephen Hawking: The Universe in a Nutshell . Deutscher Taschenbuch Verlag, Munich 2004, ISBN 3-423-34089-4 .
  • Rüdiger Vaas : Tunnel through space and time . 7th edition. Franckh-Kosmos, Stuttgart 2015, ISBN 3-440-13431-8 .
  • Kip Thorne: Warped Space and Warped Time . Droemer Knaur, Munich 1996, ISBN 3-426-77240-X .
  • Matt Visser: Lorentzian Wormholes: From Einstein to Hawking . Springer, New York / Berlin / Heidelberg 1996, ISBN 1-56396-653-0 .
  • Sunny Kalara u. a .: Blackholes, membranes, wormholes and superstrings . International Symposium on Black Holes, Membranes, Wormholes and Superstrings, Houston Advanced Research Center, USA, 16. – 18. January 1992. World Scientific, Singapore 1993, ISBN 981-02-1151-1 .
  • Paul Halpern : Holes in Space. Models for journeys through time and space . Rowohlt, Reinbek 1997, ISBN 3-499-60356-X .
  • Jim Al-Khalili : Black Holes, Wormholes and Time Machines . Spektrum Akad. Verl., Heidelberg / Berlin 2001, ISBN 3-8274-1018-5 .
  • Paul Davies : Wormholes and Time Machines . In: Sky & Telescope . tape 83 , January 1992, pp. 20-23 .
  • Michael Morris, Kip Thorne: Wormholes in space-time and their use for interstellar travel: A tool for teaching general relativity . In: Am. J. Phys. tape 56 , no. 5 , May 1988, pp. 395–412 ( physics.uofl.edu ( Memento from July 1, 2011 in the Internet Archive ) [PDF; 1.8 MB ; accessed on November 11, 2014]).
  • Stephen Hawking: Wormholes in spacetime . In: Physical Review D . tape 37 , no. 4 , 1988, pp. 904-910 ( abstract ).

Web links

Wiktionary: wormhole  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Charles W. Misner, John A. Wheeler: Classical physics as geometry . In: Annals of Physics , 2, Issue 6, 12/1957, pp. 525-603, bibcode : 1957AnPhy ... 2..525M .
  2. ^ Robert A. Fuller, John Archibald Wheeler: Causality and Multiply-Connected Space-Time. Physical Review, Volume 128, 1962, 919.
  3. ↑ Michael Morris, Kip Thorne, Ulvi Yurtsever: Wormholes, time machines and the weak energy condition. Phys. Rev. Lett., 61, 1988, 1446-1449, caltech.edu (PDF)
  4. ^ Matt Visser: Traversable worm holes: some simple examples . In: Phys. Rev. D , 39, 1989, pp. 3182-3184, arxiv : 0809.0907 .
  5. Jump up ↑ John G. Cramer, R. Forward, M. Morris, M. Visser, G. Benford, G. Landis: Natural wormholes as gravitational lenses . In: Phys. Rev. D , 51, 1995, 3117-3120, arxiv : astro-ph / 9409051 .
  6. ↑ This has already been mentioned in Morris, Thorne, Yurtsever, loc. cit. 1988, noted.
  7. ↑ First Kurt Gödel constructed cosmological solutions of the general theory of relativity with closed time-like curves (time travel).
  8. ^ Thorne: Black holes and time warps. Norton, 1994.
  9. ^ Matt Visser: The quantum physics of chronology protection. In: Gibbons u. a .: The future of theoretical physics and cosmology. Cambridge University Press, 2003 (Hawking Festschrift), arxiv : gr-qc / 0204022 .
  10. ↑ Ping Dao, Daniel Jafferis, Aron Wall: Traversable wormholes via a double trace deformation . 2016, arxiv : 1608.05687 .
  11. ↑ Natalie Wolchover: Newfound Wormhole Allows Information to Escape Black Holes . Quanta Magazine, October 23, 2017.
  12. ↑ Juan Maldacena, Douglas Stanford, Zhenbin Yang: Diving into transversable wormholes . 2017, arxiv : 1704.05333 .
  13. ↑ Susskind, Ying Zhao: Teleportation through the wormhole . 2017, arxiv : 1707.04354 .