But no one believes that entropy actually works that way. “But if that was all you knew, you’d also say that the entropy of the universe was probably larger yesterday than today - because all the underlying dynamics are completely symmetric with respect to time.” That is, if entropy is ultimately based on the underlying laws of the universe, and those laws are the same going forward and backward, then entropy is just as likely to increase going backward in time. “What Boltzmann truly explained is why the entropy of the universe will be larger tomorrow than it is today,” said Sean Carroll, a physicist at the California Institute of Technology, as we sat in a hotel bar after the second day of presentations. It accounts for the arrow of time.īut things get trickier when we step back and ask why we happen to live in a universe where such a law holds. As the Austrian physicist Ludwig Boltzmann understood in the 19th century, the second law explains why events are more likely to evolve in one direction rather than another. Entropy - a measure of the disorder in a system - always increases, a fact encoded in the second law of thermodynamics. The directionality that we observe in the macroscopic world is very real: Teacups shatter but do not spontaneously reassemble eggs can be scrambled but not unscrambled. There are a few things that everyone agrees on. But for four days, participants listened attentively to the latest proposals for tackling these questions - and, especially, to the ways in which we might reconcile our perception of time’s passage with a static, seemingly timeless universe. Most of those issues, not surprisingly, remained unresolved. Those in attendance wrestled with several questions: the distinction between past, present and future why time appears to move in only one direction and whether time is fundamental or emergent. In the latter work, mirroring Elitzur’s sentiments about the future’s lack of concreteness, Smolin wrote: “The future is not now real and there can be no definite facts of the matter about the future.” What is real is “the process by which future events are generated out of present events,” he said at the conference. His position is spelled out for a lay audience in Time Reborn and in a more technical work, The Singular Universe and the Reality of Time, co-authored with the philosopher Roberto Mangabeira Unger, who was also a co-organizer of the conference. The conference was co-organized by the physicist Lee Smolin, an outspoken critic of the block-universe idea (among other topics). Last month, about 60 physicists, along with a handful of philosophers and researchers from other branches of science, gathered at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, to debate this question at the Time in Cosmology conference. It does not! Ontologically, it’s not there.” “I don’t think that next Thursday has the same footing as this Thursday. “I’m sick and tired of this block universe,” said Avshalom Elitzur, a physicist and philosopher formerly of Bar-Ilan University. Others vehemently disagree, arguing that the task of physics is to explain not just how time appears to pass, but why. To understand the distinction between past, present and future, you have to “plunge into this block universe and ask: ‘How is an observer perceiving time?’” said Andreas Albrecht, a physicist at the University of California, Davis, and one of the founders of the theory of cosmic inflation. Many physicists have made peace with the idea of a block universe, arguing that the task of the physicist is to describe how the universe appears from the point of view of individual observers. The resulting timeless cosmos is sometimes called a “block universe” - a static block of space-time in which any flow of time, or passage through it, must presumably be a mental construct or other illusion. Moreover, they say nothing at all about the point we call “now” - a special moment (or so it appears) for us, but seemingly undefined when we talk about the universe at large. The laws that underlie these theories are time-symmetric - that is, the physics they describe is the same, regardless of whether the variable called “time” increases or decreases. Many physicists argue that Einstein’s position is implied by the two pillars of modern physics: Einstein’s masterpiece, the general theory of relativity, and the Standard Model of particle physics. Einstein’s statement was not merely an attempt at consolation.
0 kommentar(er)
