Albert Einstein's Special Theory of Relativity was initially ridiculed or ignored when he first published it in 1905.
The theory only applied to observers moving in a straight line at a constant speed and was not applicable if gravity was present or the observer was accelerating.
Einstein's famous window washer thought experiment led him to realize that gravity and acceleration were two different ways to describe the same thing.
He hypothesized that light must bend in the presence of a gravitational field, and in space, a straight line may not be the shortest path between two points.
Einstein's curved space theory became the basis of General Relativity, where gravity is not a force between massive objects but an interaction that emerges from the interaction of space and massive objects.
His theory was confirmed in 1919 when a team led by English astronomer Arthur Eddington photographed stars near the sun during a total solar eclipse and found that the theory was correct.
Albert Einstein's Special Theory of Relativity was initially ignored or ridiculed.
Gravity and acceleration were two different ways to describe the same thing.
Einstein hypothesized that light must bend in the presence of a gravitational field.
Einstein's curved space theory became the basis of General relativity.
Einstein's theory was confirmed by a team led by Arthur Eddington in 1919.
Mercury's unusual orbit was explained by Einstein's theory.
Einstein thought about what would happen if he took a flashlight or laser beam and pointed it from one side of the room to other, as the spaceship was accelerating upwards.
If he had a sensitive measuring device, he could measure the height of light on the other side of the room.
He realized that the height he would find on the other side of the room would be slightly lower than the source of light.
Einstein thought it can't be because it violates the principle of equivalence.
Acceleration of the room on a space should be no different than under the influence of gravity on earth.
He realized that this meant light must bend in the presence of a gravitational field.
But how could this be, because light always takes the shortest path between two points?
Then he realized that maybe the light IS taking the shortest path between two points, and maybe the shortest path is not a straight line.
He hypothesized that in space, perhaps a straight line is NOT the shortest path between two points, and that in the presence of mass and energy, space somehow becomes curved, so that the shortest path that light can take is a curved path.
This was the key insight that Einstein had about gravity.