In general relativity, a Roman ring (proposed by Matt Visser in 1997[1] and named after the Roman arch, a concept proposed by Mike Morris and Kip Thorne in 1988 and named after physicist Tom Roman)[2] is a configuration of wormholes where no subset of wormholes is near to chronology violation, though the combined system can be arbitrarily close to chronology violation.
Examples
[edit]For example, an Earth–Moon wormhole whose far end is 0.5 seconds in the "past" will not violate causality, since information sent to the far end via the wormhole and back through normal space will still arrive back on Earth (-0.5 + 1) = 0.5 seconds after it was transmitted; but an additional wormhole in the other direction will allow information to arrive back on Earth 1 second before it was transmitted (time travel). However, it is believed that relative time between the transmission of the information in one wormhole throat and out of the other end in a ring structure will remain the same, because light wouldn't have violated local proper time, because the distance traveled by the information would take time, either by going the long way or through the wormhole.
Chronology protection
[edit]Semiclassical approaches to incorporating quantum effects into general relativity seem to show that the chronology protection conjecture postulated by physicist Stephen Hawking fails to prevent the formation of such rings, although Matt Visser feels that there are reasons to think the semiclassical approach is unreliable here, and that a full theory of quantum gravity will likely uphold chronology protection.
Gallery
[edit]![](https://upload.wikimedia.org/wikipedia/commons/0/0e/Roman_ring_with_one_wormhole.png)
![](https://upload.wikimedia.org/wikipedia/commons/0/00/Roman_ring_with_two_wormholes.png)
![](https://upload.wikimedia.org/wikipedia/commons/c/c1/Roman_ring_with_four_wormholes.png)
Notes
[edit]- ^ Visser, Matt (1997). "Traversable wormholes: the Roman ring". Physical Review D. 55 (8): 5212–5214. arXiv:gr-qc/9702043. Bibcode:1997PhRvD..55.5212V. doi:10.1103/PhysRevD.55.5212. S2CID 2869291.
- ^ Morris M. S., Thorne K. S. (1988). "Wormholes in spacetime and their use for interstellar travel: A tool for teaching general relativity". Am. J. Phys. 56 (5): 395. Bibcode:1988AmJPh..56..395M. doi:10.1119/1.15620.
References
[edit]- Visser, Matt (1994). "van Vleck determinants: traversable wormhole spacetimes". Physical Review D. 49 (8): 3963–3980. arXiv:gr-qc/9311026. Bibcode:1994PhRvD..49.3963V. doi:10.1103/PhysRevD.49.3963. PMID 10017400. S2CID 38145051.
Well, that’s interesting to know that Psilotum nudum are known as whisk ferns. Psilotum nudum is the commoner species of the two. While the P. flaccidum is a rare species and is found in the tropical islands. Both the species are usually epiphytic in habit and grow upon tree ferns. These species may also be terrestrial and grow in humus or in the crevices of the rocks.
View the detailed Guide of Psilotum nudum: Detailed Study Of Psilotum Nudum (Whisk Fern), Classification, Anatomy, Reproduction