Overlyshastighed

Der mangler kildehenvisninger i teksten

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Overlyshastighed (også benævnt superluminal eller FTL; forkortelse for faster than light^[1]) er hastighed højere end lysets hastighed i vakuum – f.eks. subatomare partikler eller information.

Det er et teoretisk begreb, da det med den pt. (2006) kendte fysiks modeller og teorier ikke er muligt at accelerere legemer op over lysets hastighed. Grænsen skyldes Albert Einsteins relativitetsteori, som siger, at et legeme kun kan bevæge sig med lysets hastighed, hvis det ikke har nogen masse.

Partikler uden hvilemasse som f.eks. fotoner (dvs. lys) kan kun bevæge sig med præcis lysets hastighed i lufttomt rum. (Sender man fotoner ind i f.eks. glas bremses de ned).

Lys bevæger sig med samme hastighed i vakuum (uafhængigt af observatør). Ting med masse kan ikke nå op på lysets hastighed selv om visse partikler kan komme tæt på. Når hastigheden på en partikel nærmer sig lysets hastighed, bliver partiklen tungere. Når man forsøger at øge hastigheden, bliver mere og mere af den tilførte energi omsat til masse. Dette er en konsekvens af Albert Einsteins relativitetsteori.

Herudover har man til dato ikke kunnet lave reproducerbare og dermed videnskabelige eksperimenter, som fænomenologisk viser overlyshastighed, som overfører information eller fysiske objekter.

Tachyoner

Uddybende artikel: Tachyon

Som et tankeeksperiment har Gerald Feinberg teoretisk antydet, at tachyoner kan eksistere. Tachyoner er teoretiske "kvasipartikler", der bevæger sig hurtigere end lysets hastighed. De kan teoretisk eksistere, hvis de er skabt med en hastighed over lysets. De kan så bare ikke decelereres ned under lyshastigheden. Tachyoners eksistens er dog stadig en videnskabelig hypotese og er aldrig blevet observeret.^[2]

Kvantemekanik

Nogle fænomener i kvantemekanik, som f.eks. kvantefysisk sammenfiltring og kvanteteleportation, ser ud som om det overfører kvanteinformation hurtigere end lysets hastighed i vakuum. Disse fænomener tillader ikke ægte kommunikation, men de tillader dog kun at 2 observatører 2 forskellige steder i universet, ser den samme hændelse samtidigt, men uden at nogle af de 2 kan påvirke, hvad den anden ser med overlyshastighed.^[3]

Der har også været rapporteret forskellige såkaldte overlyseksperimenter baseret på kvantemekanisk tunnelering.^[4]^[5] Men de handler om måling af fasehastigheden og gruppeløbstiden, som ikke med garanti er informationshastigheden.^{[kilde mangler]}

Ormehul, rumtidstunnel

Uddybende artikel: Ormehul

Et ormehul, rumtidstunnel^[6] eller Einstein-Rosen bro er en hypotetisk egenskab af rumtiden. Hermann Weyl opstillede i 1928 en hypotese om et fænomen, som er en slags tunnel, hvor det er muligt at rejse gennem rum og tid.^[7]^[1]

Alcubierre-drev

Alcubierre drivets koncept, som viser de to rumtidsområder foran og bagved det centrale område.

Uddybende artikel: Alcubierre-drev

Et Alcubierre-drev eller Warp-drev er et science fiction-udtryk for en modificering af rumtiden om f.eks. et rumskib, så det kan flytte sig gennem rumtiden med hastigheder større end lysets (dog ikke lokalt) samtidig med at det overholder Einsteins relativitetsteori.^[1]

Se også

Kilder/referencer

^ ^a ^b ^c Defense Intelligence Reference Document. Acquisition Threat Support: 2 April 2010, Warp Drive, Dark Energy, and the Manipulation of Extra Dimensions Citat: "...In recent years, however physicists have discovered two loopholes to Einstein's ultimate speed limit: the Einstein-Rosen bridge (commonly referred to as "wormhole") and the warp drive. Fundamentally, both ideas involve manipulation of spacetime itself in some exotic way that allows for faster-than-light (FTL) travel...Essentially, the wormhole involves connecting two potentially distant regions of space by a topological shortcut. Theoretically, one would would enter the wormhole and instantaneously be transported to the exit located in a distant region of space. Although no observational evidence of wormholes exists, theoretically they can exist as a valid solution to general relativity...", backup
^ October 21, 1999, scientificamerican.com: What is known about tachyons, theoretical particles that travel faster than light and move backward in time? Is there scientific reason to think they really exist? Citat: "..."Briefly, tachyons are theoretically postulated particles that travel faster than light and have 'imaginary' masses...Tachyons have never been found in experiments as real particles traveling through the vacuum, but we predict theoretically that tachyon-like objects exist as faster-than-light 'quasiparticles' moving through laser-like media. (That is, they exist as particle-like excitations, similar to other quasiparticles called phonons and polaritons that are found in solids. 'Laser-like media' is a technical term referring to those media that have inverted atomic populations, the conditions prevailing inside a laser.)...[]..."We are beginning an experiment at Berkeley to detect tachyon-like quasiparticles. There are strong scientific reasons to believe that such quasiparticles really exist, because Maxwell's equations, when coupled to inverted atomic media, lead inexorably to tachyon-like solutions...", backup
^ December 5, 2013, news.mit.edu: You can’t get entangled without a wormhole. MIT physicist finds the creation of entanglement simultaneously gives rise to a wormhole Citat: "...Essentially, entanglement involves two particles, each occupying multiple states at once — a condition referred to as superposition. For example, both particles may simultaneously spin clockwise and counterclockwise. But neither has a definite state until one is measured, causing the other particle to **instantly** assume a corresponding state. The resulting correlations between the particles are preserved, even if they reside on opposite ends of the universe...But what enables particles to communicate instantaneously — and seemingly faster than the speed of light — over such vast distances? Earlier this year, physicists proposed an answer in the form of “wormholes,” or gravitational tunnels. The group showed that by creating two entangled black holes, then pulling them apart, they formed a wormhole — essentially a “shortcut” through the universe — connecting the distant black holes...“There are some hard questions of quantum gravity we still don’t understand, and we’ve been banging our heads against these problems for a long time,” Sonner says. “We need to find the right inroads to understanding these questions.”...This is where quantum entanglement could play a role. It might appear that the concept of entanglement — one of the most fundamental in quantum mechanics — is in direct conflict with general relativity: Two entangled particles, “communicating” across vast distances, would have to do so at speeds faster than that of light — a violation of the laws of physics, according to Einstein...", backup
^ Web archive backup: July 22, 1997, The New York Times Company: Signal Travels Farther and Faster Than Light Citat: "..."We find," Chiao Arkiveret 14. april 2005 hos Wayback Machine said, "that a barrier placed in the path of a tunneling particle does not slow it down. In fact, we detect particles on the other side of the barrier that have made the trip in less time than it would take the particle to traverse an equal distance without a barrier -- in other words, the tunneling speed apparently greatly exceeds the speed of light. Moreover, if you increase the thickness of the barrier the tunneling speed increases, as high as you please..."
^ Markus Pössel: Faster-than-light (FTL) speeds in tunneling experiments: an annotated bibliography Citat: "...An experiment of theirs, where a single photon tunnelled through a barrier and its tunneling speed (not a signal speed!) was 1.7 times light speed, is described in Steinberg, A.M., Kwiat, P.G. & R.Y. Chiao 1993: "Measurement of the Single-Photon Tunneling Time" in Physical Review Letter 71, S. 708--711..."
^ 22. februar 2015, videnskab.dk: Mælkevejen rummer muligvis tunnel til en anden verden.
^ NOVA #2612: Time Travel, Kip Thorne, Time Travel på Curlie (som bygger videre på Open Directory Project)

Eksterne henvisninger

Relativity and FTL (=Superluminal motion) Travel Homepage
Web archive backup: The Warp Drive: Hyper-Fast Travel Within General Relativity, Miguel Alcubierre Class. Quantum Grav. 11 (1994), L73-L77 Citat: "...It is shown how, within the framework of general relativity and without the introduction of wormholes, it is possible to modify a spacetime in a way that allows a spaceship to travel with an arbitrarily large speed..."
NASA: Status of "Warp Drive" Maturity – speculation Arkiveret 8. februar 2007 hos Wayback Machine

[DIA-1] Defense Intelligence Reference Document. Acquisition Threat Support: 2 April 2010, Warp Drive, Dark Energy, and the Manipulation of Extra Dimensions Citat: "...In recent years, however physicists have discovered two loopholes to Einstein's ultimate speed limit: the Einstein-Rosen bridge (commonly referred to as "wormhole") and the warp drive. Fundamentally, both ideas involve manipulation of spacetime itself in some exotic way that allows for faster-than-light (FTL) travel...Essentially, the wormhole involves connecting two potentially distant regions of space by a topological shortcut. Theoretically, one would would enter the wormhole and instantaneously be transported to the exit located in a distant region of space. Although no observational evidence of wormholes exists, theoretically they can exist as a valid solution to general relativity...", backup

[2] October 21, 1999, scientificamerican.com: What is known about tachyons, theoretical particles that travel faster than light and move backward in time? Is there scientific reason to think they really exist? Citat: "..."Briefly, tachyons are theoretically postulated particles that travel faster than light and have 'imaginary' masses...Tachyons have never been found in experiments as real particles traveling through the vacuum, but we predict theoretically that tachyon-like objects exist as faster-than-light 'quasiparticles' moving through laser-like media. (That is, they exist as particle-like excitations, similar to other quasiparticles called phonons and polaritons that are found in solids. 'Laser-like media' is a technical term referring to those media that have inverted atomic populations, the conditions prevailing inside a laser.)...[]..."We are beginning an experiment at Berkeley to detect tachyon-like quasiparticles. There are strong scientific reasons to believe that such quasiparticles really exist, because Maxwell's equations, when coupled to inverted atomic media, lead inexorably to tachyon-like solutions...", backup

[3] December 5, 2013, news.mit.edu: You can’t get entangled without a wormhole. MIT physicist finds the creation of entanglement simultaneously gives rise to a wormhole Citat: "...Essentially, entanglement involves two particles, each occupying multiple states at once — a condition referred to as superposition. For example, both particles may simultaneously spin clockwise and counterclockwise. But neither has a definite state until one is measured, causing the other particle to **instantly** assume a corresponding state. The resulting correlations between the particles are preserved, even if they reside on opposite ends of the universe...But what enables particles to communicate instantaneously — and seemingly faster than the speed of light — over such vast distances? Earlier this year, physicists proposed an answer in the form of “wormholes,” or gravitational tunnels. The group showed that by creating two entangled black holes, then pulling them apart, they formed a wormhole — essentially a “shortcut” through the universe — connecting the distant black holes...“There are some hard questions of quantum gravity we still don’t understand, and we’ve been banging our heads against these problems for a long time,” Sonner says. “We need to find the right inroads to understanding these questions.”...This is where quantum entanglement could play a role. It might appear that the concept of entanglement — one of the most fundamental in quantum mechanics — is in direct conflict with general relativity: Two entangled particles, “communicating” across vast distances, would have to do so at speeds faster than that of light — a violation of the laws of physics, according to Einstein...", backup

[4] Web archive backup: July 22, 1997, The New York Times Company: Signal Travels Farther and Faster Than Light Citat: "..."We find," Chiao Arkiveret 14. april 2005 hos Wayback Machine said, "that a barrier placed in the path of a tunneling particle does not slow it down. In fact, we detect particles on the other side of the barrier that have made the trip in less time than it would take the particle to traverse an equal distance without a barrier -- in other words, the tunneling speed apparently greatly exceeds the speed of light. Moreover, if you increase the thickness of the barrier the tunneling speed increases, as high as you please..."

[5] Markus Pössel: Faster-than-light (FTL) speeds in tunneling experiments: an annotated bibliography Citat: "...An experiment of theirs, where a single photon tunnelled through a barrier and its tunneling speed (not a signal speed!) was 1.7 times light speed, is described in Steinberg, A.M., Kwiat, P.G. & R.Y. Chiao 1993: "Measurement of the Single-Photon Tunneling Time" in Physical Review Letter 71, S. 708--711..."

[6] 22. februar 2015, videnskab.dk: Mælkevejen rummer muligvis tunnel til en anden verden.

[7] NOVA #2612: Time Travel, Kip Thorne, Time Travel på Curlie (som bygger videre på Open Directory Project)

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