Can a Message Come Back From the Past? What We Have Checked

"The book examines the problem of storing, reading and using digital documents for periods longer than 50 years."

"Die Wahrscheinlichkeit, dass es in einigen Jahren noch Systeme und Programme gibt, die solche Daten lesen können, ist somit deutlich höher."

"garantiert das richtige Erscheinungsbild des Dokuments für eine Langzeitarchivierung."

"While we are rapidly advancing from vulnerable physical solutions to superior, digital media, preserving and using data over the long term involves complicated research challenges and organization efforts."

"Die hohen Kosten, die durch diese Pflege der Datenbestände entstehen, haben allerdings zur Folge, dass nur die wichtigsten Daten derart konserviert werden können."

"Nicht erlaubt sind Referenzen auf Ressourcen, die nicht in der Datei enthalten sind. Alle verwendeten Bilder und Schriftarten (die Begrenzung auf die verwendeten Zeichen ist erlaubt) müssen in der PDF-Datei enthalten sein."

"Die Vermutung zum Schutz der Zeitordnung bzw. der Zeitfolge (engl. chronology protection conjecture bzw. CPC) wurde von Stephen Hawking formuliert, da in einigen Lösungen für die Gleichungen der Allgemeinen Relativitätstheorie geschlossene zeitartige Kurven (engl. closed timelike curves bzw. CTC) auftauchen und diese die Möglichkeit von Zeitreisen auf der Zeitachse rückwärts beinhalten."

"2009 zeigten dieselben Autoren zusammen mit James Dent, dass solche Raumzeit -Szenarien im Prinzip geschlossene zeitartige Kurven ( Zeitreisen ) ermöglichen könnten."

""At last a way to test time travel" , New Scientist 2552 p. 34, 20. Mai 2006 von Marcus Chown"

"As a model of physical reality it can therefore be dismissed because it is unlike the universe we live in."

"2005 diskutierte er zusammen mit Thomas Weiler und Sandip Pakvasa die Möglichkeit, dass sterile Neutrinos Abkürzungen in Extra-Dimensionen nehmen könnten."

"Another simple space-time containingCTCs is that of van Stockum [2] which representsa cylinder of rigidly rotating dust; however, the cylinder is of infinite length so it could not be realised in practice."

"Nearly all of these have been regarded as of merely theoretical interest because of some non-physi"

"in default of a reasonable interpretation of CTC, general relativity does not give a satisfactory account of all phenomenawithin its terms of reference."

"Bereits 1862 wurde im Johannisturm in Aschersleben eine Zeitkapsel in Form einer Blechbüchse mit sechs verschiedenen Urkunden gefunden, wovon die älteste auf 1599 datiert wurde und diverse Informationen zur Geschichte der Stadt enthalten waren."

"Ein Schriftstück vom 12. Juli 1652 beschrieb beispielsweise die Leiden durch den Dreißigjährigen Krieg in Aschersleben, in anderen Schriften wird vom Auftreten der Pest berichtet."

"die im Jahr 1940 in einem aufgelassenen Schwimmbad an der Oglethorpe University verschlossen wurde und erst im Jahr 8113 geöffnet werden soll."

"Capello said that nearly every item inside had been affected by water, mold, and mildew."

"Moisture that seeped through the Public Square capsule's rusted steel container damaged a stack of documents about 10 inches high. Those papers were stuck together and moldy, so they were not salvageable, but at least 200 documents were saved."

"When the capsule was finally opened, much of what had been placed inside 50 years ago was wet, stained, stuck together or destroyed."

"The plan has now been scrapped after the city discovered earlier this month that water and mold had damaged nearly all of the objects inside the capsule."

""It was heartbreaking," she said."

"Both had been dug up and opened before the events so staff could check the condition of the capsules and their contents."

"“Boy, everything is sure water damaged,” Krueger said. “Really disappointed in this.”"

"When the capsule lid was removed the next day, they saw that more than half of the vessel was filled with water, Kolb recounted. Even the plastic bags inside the capsule were breached, he said."

""That's a very sturdy time capsule, and we had no idea that it would leak or have any kind of a failure," he said."

"The other, buried outside the Washington County Museum of Fine Arts, was opened Tuesday ."

"“I am crying. I’m not sure what to say. I’m heartbroken.”"

"According to a news article at the time, the vault was “water-proofed.” However, that turned out not to be the case – a fact that the city only discovered earlier this month."

"Historical Society archivist Shane Keenan said the artifacts were preserved better than most were expecting with the water damage."

"The vault is currently being drained,” the city shared in a social media post."

"“There was a little water that ran out, about a gallon or so, so I don’t know if there’s any damage in there or not,” she said."

"“We were all really disappointed there wasn’t more material that was recoverable,” said Bill Kolb, Mountain View’s assistant library director."

""We'll probably put a plaque out at the Liberty Pole at Coleman Memorial Park saying it's because of damage it's been moved to City Hall," she said."

"On the outside, it is a small, metal box, corroded and dented."

"Workers used X-rays to locate the copper box inside the concrete cornerstone without damaging the exterior marker, then jackhammered it out approximately four weeks prior to the opening."

"The copper box, originally placed during a hospital expansion cornerstone ceremony on September 10, 1952, contained, blueprints, a Bible, historical pictures, photographs and additional legal and historical documents from the era."

"The causal relations between points in the manifold are interpreted as describing which events in spacetime can influence which other events."

"Sending a qubit into the past by a P-CTC is somewhat like teleporting the qubit’s state"

"A closed timelike curve is a closed curve which is everywhere future-directed timelike (or everywhere past-directed timelike)."

"describes a worldline in spacetime looping back on itself, allowing a particle to return to and interact with its own past"

"Bennett and Schumacher’s postselected quantum teleportation is a model of closed timelike curves (CTCs) that leads to results physically different from Deutsch’s model."

"A closed null curve is a closed curve which is everywhere future-directed null (or everywhere past-directed null)."

"existence of closed timelike curves (CTCs) [1–4]"

"in which the future existence of a P-CTC might affect the present outcome of an experiment."

"because then the future events must produce the past events but also the past events must produce the future events"

"Unconditionallysecurebitcommitmentisforbiddenbyquantummechanics."

"Alice locks a secret bit into a safe that"

"‘immutable timeline retrocausality,’ where an event in the present having a retrocausal influence on the past can’t change anything about the present because its retrocausal influence has already been exerted"

"Now as explored by Price in ref [15], it transpires that the kind of retrocausality needed to explain the Bell correlations actually can’t be used to create causal paradoxes of this kind"

"The possibility that the laws of physics might allow for the existence of closed time-like curves (CTCs) inside our universe has been a long time conjecture [1], which has been more recently revived by a series of papers [2–15]."

"Wormhole simulations revealed that stability is highly dependent on negative energy densities, aligning with theoretical predictions but constrained by the absence of observable exotic matter."

"One of the main ideas being studied is the “closed timelike curve,” a theoretical loop in spacetime predicted by Albert Einstein’s theory of relativity. According to scientists, such loops could potentially allow information to return to an earlier point in time without violating known physical laws."

"Provided the matter density in some regions of our universe satisfies certain properties (i.e. it violates the so-called ‘averaged weak energy conditions,’ see, e.g., Refs. [3–6]), these 4-d Lorentzian wormhole geometries could, in principle, exist (at least they can be exact solutions of the Einstein equations)."

"In some studies, photons appeared to exchange information in ways that seemed retroactive, though researchers emphasised that no actual human or object travelled through time."

"It states that the only solutions to the laws of physics that can occur in spacetimes containing closed timelike curves are those that are globally self-consistent"

"if the wormhole is traversed from mouth to mouth, it acts as a ‘time machine’ allowing one to travel into the past or into the future."

"and no locally initiated event can create a contradiction."

"This requirement has been explicitly formulated as the ‘Principle of self-consistency,’ according to which the only solutions to the laws of physics that can occur locally in the real universe are those which are globally self-consistent [7, 9, 13–15]."

"the only possible trajectories (for a particle with fixed initial and final positions and which traverses the wormhole once) minimizing the classical action are those which are globally self-consistent, and that the ‘Principle of self-consistency’ (originally introduced by Novikov) is thus a natural consequence of the ‘Principle of minimal action.’"

"The canonical example: a traveller acquires a document at time t₂, travels to t₁ < t₂, and delivers that document to an agent who publishes it, so that the traveller can read it at t₂."

"Crucially, Novikov and colleagues observe that self-consistent solutions to such loops arise naturally from the imposition of fixed-point boundary conditions [1]."

"The central idea of the emulation strategy is to emulate obsolete systems on future, unknown systems, so that a digital document's original software can be run in the future despite being obsolete."

"There is as yet no viable long-term strategy to ensure that digital information will be readable in the future."

"The view path model requires extensions of the metadata sets of the primary object as well as additionally stored secondary objects resulting in a reproduction of the object's environment, e.g. applications or operating systems."

"Format registries such as PRONOM and the Library of Congress's Sustainability of Digital Formats initiative provide guidance on which formats are most likely to remain accessible and which require active management."

"It can act as a complement to the otherwise dominant digital preservation strategies of migration and has convincing advantages, especially for dynamic digital objects."

"Checksum verification, in which a mathematical fingerprint is calculated for each file and periodically rechecked, allows institutions to detect silent corruption, known as bit rot, before it spreads."

"redundancy and geographic distribution, which ensure that multiple copies of digital objects exist in different locations and on different media, reducing the risk of loss from disaster or media failure."

"The idea goes back at least to the 1960s, when physicist Gerald Feinberg tried to give faster-than-light particles a formal place in theory."

"If a tachyon could outrun light, then under some circumstances different observers could disagree about the order of events. A particle emitted in one frame of reference could look, in another, like it was absorbed before it was ever sent."

"That kind of reversal fed the old fear that tachyons would demolish causality itself."

"The causal self-consistency condition for closed timelike curves can give rise to nonlinear interactions on chronology-respecting qubits."

"Gott spacetime has closed timelike curves, but no locally anomalous stress-energy."

"by switching on his detector at latter times he will still be able to access information that is kept encoded in the field."

"In principle, he can transmit an arbitrarily large amount of classical information with a quantum system of fixed size."

"The resultant interacting quantum field theory is not unitary because the field operators can create real, on-shell, particles in the acausal region."

"As a result, the effective potential within the acausal region is complex, and probability is not conserved."

"Closed timelike curves (CTCs) are trajectories in spacetime that effectively travel backwards in time: a test particle following a CTC can in principle interact with its former self in the past."

"CTCs appear in many solutions of Einstein’s field equations and any future quantum version of general relativity will have to reconcile them with the requirements of quantum mechanics and of quantumfieldtheory."