The quote states that we should be using solar energy before our limited amount of naturally occurring oil and coal runs out. Meaning; we should be proactively working towards solar power rather than to wait for our resource to run out to start.
Answer: It is used to show the force between two objects caused by gravity.
Explanation: The gravitational constant appears in Isaac Newton's universal law of gravitation.
{\displaystyle G}{\displaystyle G} is about 6.67430×10−11 N⋅m2/kg2,[1] and is denoted by letter G