How we know that Einstein's General Relativity can't be quite right

Einstein's theory of General Relativity tells us that gravity is caused by the curvature of space and time. It is a remarkable theory that has been confirmed by countless observations, such as gravitational lensing, light deflection on the sun, redshift in the gravitational potential, black holes and their shadows, and gravitational waves. However, we already know that General Relativity cannot be quite right because it does not fit together with another well-confirmed theory that is quantum mechanics. To resolve this tension, physicists think that we need a theory of quantum gravity. In this video I explain the three key reasons why physicists think that we need a theory of quantum gravity.

https://youtu.be/Ov98y_DCvRY

A new way to visualize General Relativity

How to faithfully represent general relativity ? Is the image of the rubber sheet accurate ? What is the curvature of time ? All these answers in 11 minutes !
https://youtu.be/wrwgIjBUYVc

A star orbiting the Milky Way's black hole validates Einstein | Science News

The first sign that Albert Einstein’s theory of gravity was correct has made a repeat appearance, this time near a supermassive black hole.....
https://www.sciencenews.org/article/star-orbiting-milky-way-giant-black-hole-confirms-einstein-was-right

It turns out Albert Einstein was pretty smart after all - CNN

While general relativity has been accepted as a theory that applies to our solar system, the scope of its effect on a larger scale has until now been a mystery, writes Don Lincoln ....
https://www.cnn.com/2018/06/26/opinions/einstein-ring-opinion-lincoln/index.html