From the past few nights, the Tribute in Light has been lighting up the lower Manhattan sky for testing. According to the city, the testing will continue through tonight, "On Sept. 11, the lights will be turned on at 6:00 pm and remain on until 8:00 am on the morning of Sept. 12. The lights will point straight up and will remain static." The installation is set up on top of a parking garage on West and Edgar Streets, but can be seen from downtown Manhattan, Brooklyn and NJ.

As for the city's other events commemorating the eighth anniversary of the September 11 attacks, the official ceremony is at Zuccotti Park, where the names of the 2,752 victims will be read by victims' relatives and volunteers. Moments of silence will be held at 8:46 a.m. (observance of time first plane struck North Tower), 9:03 a.m. (when the second plane struck South Tower), 9:59 a.m. (when the South Tower fell) and 10:29 a.m. (when the North Tower fell). Relatives and survivors will also be allowed to descend into the "pit" at Ground Zero to pay their respects and lay flowers.

Tomorrow is also a National Day Service—there are many volunteer opportunities around the city. And the National September 11 Memorial and Museum's preview site is open to visitors.