Gravity Timeline - Timeline

Newton Publishes His Book (1687) The book outlines the universal law of gravity, and finally made accurate predictions of planetary motion.

Pseudo-Planet (1859) Urbain Le Verrier observed the strange orbit of Mercury. He proposed that a planet called "Vulcan" must exist, and would account for the oddities of Mercury's orbit. No such planet would ever be observed, but rather Einstein's theories would later explain the observations.

Early Concepts of Gravity (4th Century BCE) Very early Greek/Indian concepts from philosophers such as Aristotle described gravity as some intrinsic property of heavy bodies (Earth) versus light bodies (fire). Heavy objects were also believed to fall faster. These beliefs were held for nearly 2000 years.

Galileo Galilei (1600s) Gelileo found that all objects accelerate equally towards Earth in free fall; regardless of their weight.

Theory of Relativity (1905-1915) Albert Einstein would redefine physics; he proposes mass and energy are equivalent. Gravity is the result of the warping of spacetime, predicts gravitational waves, & black holes. This theory was strengthened when it predicted Mercury's orbit, as previously mentioned.

Gravitational Lensing (1919) Einstein's theory would indicate that large enough bodies would bend light. This was confirmed when in 1919, during the total solar eclipse, stars near the sun were apparently out of position. The sun's large mass would account for the light bending.

Hawking Radiation (1974) Einstein's theory conflicted with quantum physics. The boundary of a black hole couldn't exist in the smooth spacetime, if the black hole is composed of granular energy required by quantum physics. Hawking solved this with Hawking Radiation: black holes are emitting energy. Quantum Gravity is still a working concept.

Gravitational Wave False Alarm (1969) Joseph Weber claimed he had detected gravitational waves. These waves were predicted in Einstein's Theory of General Relativity,but Weber's results could not be reproduced.

Muslim Scientists (1000s) Muslim physicists, mathematicians, & astronomers began advancing parts of physics. Al-Biruni argued that all heavenly bodies have mass & gravity like Earth, criticizing Aristotle and previous Muslim Scholars. Ibn Bajjah proposed a very early version of the third law of motion (every action has an equal & opposite reaction). However, Bajjah, like Galileo, would attempt to explain planetary orbits without gravity. These ideas wouldn't be widely accepted until later.

Gravitational Waves Confirmed (2016) After rigorous checks, the LIGO team confirmed that they had detected gravitational waves.