Many physicists argue that Einstein\u2019s position is implied by the two pillars of modern physics: Einstein\u2019s masterpiece, the general theory of relativity, and the Standard Model of particle physics. The laws that underlie these theories are time-symmetric \u2014 that is, the physics they describe is the same, regardless of whether the variable called \u201ctime\u201d increases or decreases. Moreover, they say nothing at all about the point we call \u201cnow\u201d \u2014 a special moment (or so it appears) for us, but seemingly undefined when we talk about the universe at large. The resulting timeless cosmos is sometimes called a \u201cblock universe\u201d \u2014 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.<\/p>\n
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. To understand the distinction between past, present and future, you have to \u201cplunge into this block universe and ask: \u2018How is an observer perceiving time?\u2019\u201d said <\/span>Andreas Albrecht<\/a>, a physicist at the University of California, Davis, and one of the founders of the theory of <\/span>cosmic inflation<\/a>.<\/p>\n Others vehemently disagree, arguing that the task of physics is to explain not just how time appears to pass, but why. For them, the universe is not static. The passage of time is physical. \u201cI\u2019m sick and tired of this block universe,\u201d said <\/span>Avshalom Elitzur<\/a>, a physicist and philosopher formerly of Bar-Ilan University. \u201cI don\u2019t think that next Thursday has the same footing as this Thursday. The future does not exist. It does not! Ontologically, it\u2019s not there.\u201d<\/p>\n Last month, about 60 physicists, along with a handful of philosophers and researchers from other branches of science, gathered at the <\/span>Perimeter Institute for Theoretical Physics<\/a> <\/span>in Waterloo, Canada, to debate this question at the <\/span>Time in Cosmology<\/a> <\/span>conference. The conference was co-organized by the physicist <\/span>Lee Smolin<\/a>, an outspoken critic of the block-universe idea (among <\/span>other topics<\/a>). His position is spelled out for a lay audience in <\/span>Time Reborn<\/a><\/i> <\/span>and in a more technical work, <\/span>The Singular Universe and the Reality of Time<\/i><\/a>, co-authored with the philosopher <\/span>Roberto Mangabeira Unger<\/a>, who was also a co-organizer of the conference. In the latter work, mirroring Elitzur\u2019s sentiments about the future\u2019s lack of concreteness, Smolin wrote: \u201cThe future is not now real and there can be no definite facts of the matter about the future.\u201d What is real is \u201cthe process by which future events are generated out of present events,\u201d he said at the conference.<\/p>\n