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"OH WATERS, TEEM WITH MEDICINE TO KEEP MY BODY SAFE FROM HARM, SO THAT I MAY LONG SEE THE SUN." - Rig Veda
não é um filme. É um livro com imagens.
tempo que não via um filme que gostasse tanto.
Just last year, physicist John Howell and his team from the University of Rochester . In the Rochester setup, laser light was measured and then shunted through a beam splitter. Part of the beam passed right through the mechanism, and part bounced off a mirror that moved ever so slightly, due to a motor to which it was attached. The team used weak measurements to detect the deflection of the reflected laser light and thus to determine how much the motorized mirror had moved.
That is the straightforward part. Searching for backward causality required looking at the impact of the final measurement and adding the time twist. In the Rochester experiment, after the laser beams left the mirrors, they passed through one of two gates, where they could be measured again—or not. If the experimenters chose not to carry out that final measurement, then the deflected angles measured in the intermediate phase were boringly tiny. But if they performed the final, postselection step, the results were dramatically different. When the physicists chose to record the laser light emerging from one of the gates, then the light traversing that route, alone, ended up with deflection angles amplified by a factor of more than 100 in the intermediate measurement step. Somehow the later decision appeared to affect the outcome of the weak, intermediate measurements, even though they were made at an earlier time.
This amazing result confirmed a similar finding by physicists Onur Hosten and Paul Kwiat at the University of Illinois at Urbana-Champaign. They had achieved an even larger laser amplification, by a factor of 10,000, when using weak measurements to detect a shift in a beam of polarized light moving between air and glass.
For Aharonov, who has been pushing the idea of backward causality for four decades, the experimental vindication might seem like a time to pop champagne corks, but that is not his style. “I wasn’t surprised; it was what I expected,” he says.
Tollaksen sums up this confounding argument with one of his favorite quotes, from the ancient Jewish sage Rabbi Akiva: “All is foreseen; but freedom of choice is given.” Or as Tollaksen puts it, “I can have my cake and eat it too.” He laughs.
Is feedback from the future guiding the development of life, the universe, and, well, everything? Paul Davies at Arizona State University in Tempe and his colleagues are investigating whether the universe has a destiny—and if so, whether there is a way to detect its eerie influence.
Cosmologists have long been puzzled about why the conditions of our universe—for example, its rate of expansion—provide the ideal breeding ground for galaxies, stars, and planets. If you rolled the dice to create a universe, odds are that you would not get one as handily conducive to life as ours is. Even if you could take life for granted, it’s not clear that 14 billion years is enough time for it to evolve by chance. But if the final state of the universe is set and is reaching back in time to influence the early universe, it could amplify the chances of life’s emergence.
With Alonso Botero at the University of the Andes in Colombia, Davies has used mathematical modeling to show that bookending the universe with particular initial and final states affects the types of particles created in between. “We’ve done this for a simplified, one-dimensional universe, and now we plan to move up to three dimensions,” Davies says. He and Botero are also searching for signatures that the final state of the universe could retroactively leave on the relic radiation of the Big Bang, which could be picked up by the Planck satellite launched last year.