For a brief, (literally) shining moment yesterday, the first functioning half of Michael Arad’s “Reflecting Absence” memorial at the World Trade Center site was tested. That meant running some 26,000 gallons of water a minute over the 30-foot-deep black granite walls that outline the footprint of the lost North Tower. The test of the one-acre fountain went off without a hitch, according to the Post, and even the volume of the splashing water (initially a concern of designers) turned out to be at a soothing — rather than deafening — level. Eventually a second, twin, acre-sized fountain will be completed in the footprint of the South Tower, and trees will be planted surrounding them. Also, a bronze placard including all the names of those who died in the 9/11 attacks will be constructed and backlit so the names can be read at night.