Tonight at 6 p.m. the Guggenheim presents a marathon symposium titled "24-Hour Program on the Concept of Time." The museum's chief curator Nancy Spector organized the event in the mold of Hans Ulrich Obrist, who has presided over similar symposia in other cities, most recently a "mini-marathon" in Beijing on New Year's Eve that lasted a measly 12 hours. Like its predecessors, the 24-Hour Program is presented in an art-world context but brings together thinkers across many disciplines. Tonight's (and tomorrow's) lineup of speakers includes Ronald Mallett, a physicist who has devoted his life to building a time machine, and Joseph LeSauteur, an expert in the psychology of circadian rhythms. Also slated to participate are Philippe Parreno, Angela Bulloch, and Liam Gillick, artists featured in the exhibition upstairs whose run will end when the symposium does. "theanyspacewhatever" is about ten artists who emerged in the 1990s, but it doesn't show any 1990s art. Instead, it comprises new installations conceived specifically for the Guggenheim's rotunda. That should give a clue about these artists' attitude toward temporality. Over their careers they have avoided producing static, stand-alone objects, which are doomed to become relics or fetishes over time, while proposing that art lies in the viewer's reception of a proposition made by the artist at a specific place and time. Obrist conceived his experimental symposia with a similar sensibility -- which makes sense, since he is of the same generation and matured in the same intellectual milieu -- but when "theanyspacewhatever" turned out to be so undemanding that it was largely written off by many as a bore, one wonders what the artists will have to say about the marathon's punishing spatial and temporal parameters -- respectively, a darkened theater and a full rotation of the Earth. This Rhizome correspondent will attend and report back in the near future. - Brian Droitcour