Answer:Artificial light from cities has created a permanent "skyglow" at night, obscuring our view of the stars. Here's their map of artificial sky brightness in North America, represented as a ratio of "natural" nighttime sky brightness. In the black areas, the natural night sky is still (mostly) visible.
Explanation:
With a pH of five, it would mean that this substance is a weak acid one would also it expect it would be sour.
Remember pH=-log(H ions). So it would be pH=-log(10^-7).
