Of the many forms of pollution caused by humans, none is more obvious than the misuse of lighting. Unwanted and unwelcome light trespass began with the invention of the electric light and has expanded in proportion to the electrification of the planet (see Physics Today, June 2005, page 24). The major sources of light pollution include street lighting, outdoor sports arenas, the promotional lighting of buildings and monuments, and car sales lots.Simply put, light pollution is blinding ground-based astronomy. Extensive light pollution is gradually and inexorably reducing the quality and utility of astronomical observations made from major observatories all over the planet. To add insult to injury, more recently a number of medical researchers have discovered a correlation between extensive light pollution and an emerging number of serious human disorders. 1 1. See, for example, B. Harder, Science News 169, 8 (2006) https://doi.org/10.2307/3982282. The International Dark-Sky Association (IDA) was founded by Kitt Peak astronomer David Crawford more than 18 years ago, and is made up of concerned astronomers and others who are accepting the challenge to slow down the continually advancing march toward brighter and brighter night skies. The IDA has taken the unusual stance of enlisting the major utilities, lighting manufacturers’ associations, professional lighting engineering societies, and municipalities in finding better ways to achieve the objectives of lighting for safety and commerce without denigrating the natural dark sky environment. Organizations that have joined in supporting the IDA include the Illuminating Engineering Society of North America, the International Association of Lighting Designers, the Illuminating Engineering Society of Australia and New Zealand, and the Vienna-based International Commission on Illumination. Although adopting coherent and effective lighting ordinances can provide immediate gains—including less energy consumption, improved security, and reductions in glare and light trespass—the improvement in preserving our dark skies for astronomical research is insufficient. The institution that has the responsibility to advance astronomical sciences in the US is the venerable American Astronomical Society. However, that organization is failing to address the problem. Although AAS has always agreed with the goals of the IDA and has written numerous papers and articles in support of the IDA’s efforts to reduce light pollution, it has failed to aggressively encourage its members to join and support the IDA. Of all the members of the physics community, AAS has the most to lose by not directly supporting the IDA.I call on the US physics community and all readers of Physics Today to support the IDA, with your time and treasury, and to actively engage in any of the IDA’s many sections throughout the world. Failure to act today will doom future generations from ever experiencing the wonder of seeing the stars from a dark and natural site and will ensure that the dark skies can only be experienced through planetariums and other artificial media. Astronomers of the future will only speculate on why this generation did not take the lead in protecting our dark skies when the opportunity was so clearly and readily available. [Editor’s note: We invited a response from Craig Wheeler, president of the American Astronomical Association, and Kevin Marvel, AAS’s executive officer.] REFERENCESection:ChooseTop of pageREFERENCE <<1. See, for example, B. Harder, Science News 169, 8 (2006) https://doi.org/10.2307/3982282. Google ScholarCrossref© 2006 American Institute of Physics.