There are also cultural and economic reasons for concern about excessive light at night. Skyglow prevents large fractions of the Earth's population from viewing the Milky Way,[6] which drove the development of much of ancient science, mythology, and religion. In the US, the cost of generating wasted light is estimated to be 7 billion US dollars per year;[7] the production of the electricity for this wasted light also results in the release of chemical pollution and greenhouse gases.