Carlo Rovelli and Lee Smolin have recently taken diametrically opposed positions on whether time is a basic part of reality or merely an emergent feature----like for example temperature, or the surface of a liquid. The surface of a liquid is well-defined at our macro scale, but if you look closely it does not exist. Likewise the temperature is only meaningful at macroscopic scale, when the system has a lot of degrees of freedom. It is said to be an emergent property of matter, not a fundamental property. By analogy, time might be emergent. It might not exist at a fundamental level. Rovelli thinks that at the fundamental level there are only correlations between observables----several of these observables can be used as alternative clocks, and the others (like position etc.) can be correlated with them. But he questions whether there is a ONE RIGHT CLOCK. Maybe there is no one unique big clock that we can distinguish as the master timekeeper. And so time, in the abstract, does not exist. There are only many more or less good quantum observables that you can use, and correlate other observations to them, to keep track. Rovelli develops this viewpoint in an August 2008 essay that FQXi has put online. "Forget Time" http://fqxi.org/community/forum/topic/237 when you click on PDF you get the full 7 page essay http://fqxi.org/data/essay-contest-files/Rovelli_Time.pdf This idea that time is not fundamental, does not exist at the level of basic description of nature, seems pretty reasonable. But Lee Smolin argues persuasively against it in this video lecture. The Reality of Time and the Evolution of Laws. Here is the main page, with links to the online video lecture and the slides PDF http://pirsa.org/08100049/ Here is just the slides PDF, if you want to read the gist of the talk. http://pirsa.org/index.php?p=media&url=/pdf/files/68863c39-f22d-430f-991d-bb8d224440ad.pdf He agrees that you can get rid of time for describing all subsystems of the universe, but you cannot, he argues, dispense with time in a fundamental description of the universe as a whole. This is a subtle and interesting point. As long as there is an outside observer looking at an isolated subsystem, as if in a laboratory, there is always the observer's clock---the clock on the laboratory wall. But how to deal with the situation where there is no isolated experiment, no outside observer, no setup with initial conditions, no reliable eternal laws but instead the natural history of this one unique world with more or less regular patterns of behavior. If we picture this as resembling the laboratory experiment, which we can repeat with different initial conditions, then (suggests Smolin) we are fooling ourselves. So, he argues, we cannot get rid of time in the way we are used to, as if inside the box of a subsystem.