Switching a lot of our energy consumption to renewable forms would significantly help the planet because it doesn’t put out pollution or waste, and doesn’t use the resources we are low on like coal or gas. Forms of renewable energy to switch to would be solar energy, wind energy, or hydroelectricity.
Measuring in light-years also allows astronomers to determine how far back in time they are viewing , Because light takes time to travel to our eyes. Everything we view during the dark in night has already been happened.
A. Gravity is the answer I got you!!!