LEDs and light pollution
In 1962, Nick Holonyak, Jr. invented the first visible light LED (see US Patent No. 4,270,094). Fast forward to today and incandescent lights are being replaced with LEDs because LEDs are energy efficient (and as a bonus they save money over their liftetime).
However, as with everything good, there is a downside. Because people are saving money, they are not replacing lights on a 1-1 basis. Rather, they are adding more LEDs. This is causing a worsening light pollution problem (see link 1, link 2).
As an aside, the change to LED lights also affects movie making (see link).
Photo by Marc Mueller licensed under CC0 (link).