Posts tagged time travel
“It’s slippery in here”
“The Future was better protected than the Past” —La Jetée (1962)
“The Future was better protected than the Past”
worst TARDIS ever!
“We’re still trying to figure out what time is,” Gleick said. Time travel stories apparently help us. The inventor of the time machine in Wells’s book explains archly that time is merely a fourth dimension. Ten years later in 1905 Albert Einstein made that statement real. In 1941 Jorge Luis Borges wrote the celebrated short story, “The Garden of Forking Paths.” In 1955 physicist Hugh Everett introduced the quantum-based idea of forking universes, which itself has become a staple of science fiction.
“Time,” Richard Feynman once joked, “is what happens when nothing else happens.” Gleick suggests, “Things change, and time is how we keep track.” Virginia Woolf wrote, “What more terrifying revelation can there be than that it is the present moment? That we survive the shock at all is only possible because the past shelters us on one side, the future on another.”
“Enjoy the present. Don’t waste your brain cells agonizing about lost opportunities or worrying about what the future will bring. As I was working on the book I suddenly realized that that’s terrible advice. A potted plant lives in the now. The idea of the ‘long now’ embraces the past and the future and asks us to think about the whole stretch of time. That’s what I think time travel is good for. That’s what makes us human — the ability to live in the past and live in the future at the same time.”
The ability to remember the past and imagine the future can significantly affect a person’s decisions in life. Scientists refer to the brain’s ability to think about the past, present, and future as “chronesthesia,” or mental time travel, although little is known about which parts of the brain are responsible for these conscious experiences. In a new study, researchers have used functional magnetic resonance imaging (fMRI) to investigate the neural correlates of mental time travel and better understand the nature of the mental time in which the metaphorical “travel” occurs.
Closed timelike curves are among the most controversial features of modern physics. As legitimate solutions to Einstein’s field equations, they allow for time travel, which instinctively seems paradoxical. However, in the quantum regime these paradoxes can be resolved leaving closed timelike curves consistent with relativity. The study of these systems therefore provides valuable insight into non-linearities and the emergence of causal structures in quantum mechanics-essential for any formulation of a quantum theory of gravity. Here we experimentally simulate the non-linear behaviour of a qubit interacting unitarily with an older version of itself, addressing some of the fascinating effects that arise in systems traversing a closed timelike curve. These include perfect discrimination of non-orthogonal states and, most intriguingly, the ability to distinguish nominally equivalent ways of preparing pure quantum states. Finally, we examine the dependence of these effects on the initial qubit state, the form of the unitary interaction, and the influence of decoherence.
Time travel has captured the public imagination for much of the past century, but little has been done to actually search for time travelers. Here, three implementations of Internet searches for time travelers are described, all seeking a prescient mention of information not previously available. The first search covered prescient content placed on the Internet, highlighted by a comprehensive search for specific terms in tweets on Twitter. The second search examined prescient inquiries submitted to a search engine, highlighted by a comprehensive search for specific search terms submitted to a popular astronomy web site. The third search involved a request for a direct Internet communication, either by email or tweet, pre-dating to the time of the inquiry. Given practical verifiability concerns, only time travelers from the future were investigated. No time travelers were discovered. Although these negative results do not disprove time travel, given the great reach of the Internet, this search is perhaps the most comprehensive to date.