Short answers, pulled from the story.
The 7th-century Indian astronomer Brahmagupta was the first Indian scholar to explicitly describe gravity as an attractive force, writing that it is the nature of the Earth to attract and keep things. The Greek philosopher Plutarch earlier noted that gravitational attraction might not be unique to Earth, suggesting the Sun and Moon also attract the parts that compose them.
The theory of impetus, first proposed by John Philoponus in the 6th century AD, held that a mover imparts a causative force to a moving object that sustains its motion and diminishes over time. It replaced Aristotle's claim that motion requires continuous external force. Ibn Sina refined it in the 11th century, arguing the impetus was persistent rather than temporary, which foreshadowed the modern concept of inertia.
Edmond Halley visited Newton in the summer of 1684 and asked what trajectory an inverse-square force would produce. Newton said an ellipse. By November 1684 Newton sent Halley a paper mathematically deriving Kepler's laws. Halley then supported Newton through the publication process, and the Principia appeared in 1687. The book sold out quickly, leading Newton to publish a second edition in 1713.
Arthur Eddington observed gravitational lensing of starlight around the Sun during a total solar eclipse on the 29th of May 1919. The bending of light matched Einstein's equations, not Newton's predictions. This confirmation was widely reported and established general relativity as the successor to Newtonian physics.
Dark energy is a concept for the negative pressure field thought to drive the accelerating expansion of the universe. Alan Guth and Alexei Starobinsky proposed in 1980 that such a field could have driven cosmic inflation in the early universe. In 2013, measurements found that dark energy composed around 68.3% of the early universe's total energy content.
General relativity is incompatible with quantum mechanics. At short distances on the order of the Planck length, the standard quantum field theory approach to gravity, which models gravitational attraction as exchange of virtual gravitons, breaks down. No fully consistent theory unifying gravity with the other fundamental forces has yet been confirmed.