sentence: Gravity gets stronger as something gets bigger or more massive.
sentences_before: In 1783, an English geologist named John Mitchell wrote that it might be possible for something to be so big and heavy that the escape speed from its gravity is equal to the speed of light.
sentences_after: For a small thing, like a rocket, to escape from a larger thing, like Earth, it has to escape the pull of our gravity or it will fall back. The speed that it must travel upward to get away from Earth's gravity is called escape velocity. John Mitchell thought it was possible for something to be so big that the escape velocity would be faster than the speed of light, so even light could not escape.
concept_name: gravity
headings: Black hole History
categories: Stars Astrophysics