Thanks to YouTube suggestions I saw some videos.
- One is about the bright spot in the middle of a coin shadow, which is called the Poisson spot, that is related to light diffraction. (https://youtu.be/y9c8oZ49pFc)
- The other is about Einstein's curvature of space-time and the proof derived from the experiment with bent light from the hidden star. (https://youtu.be/-m3SddsTSAY?t=1m11s or https://youtu.be/nhAUiLLMAsk?t=2m25s)
And I noticed some discrepancy. Since light propagates as waves, the experiment with the hidden star can be explained by light diffraction.
I've tried to google that issue with no luck. So the question is:
Is the effect of the hidden star can be explained by light diffraction?
And what about Space-time curvature then? is it a fake?
I'm neither a mathematician nor physicist. So I do not make statements. But from what I intuitively feel, what Einstein did was the ingenious math trick. He replaced an unknown force, gravity, by some mathematical expression, so that a result of calculation stays correct. And by introducing the concept of space-time curvature he didn't explain the phenomena of the gravity itself. He just swept the issue under the rug. Even if a mass causes space to bend, what force causes the mass to bend space? So we came to where we started. Although this concept is incredible, it's mind-boggling as well. Since human imagination is based on the vision and the vision is three dimensional, hardly anyone can clearly operate this four-dimensional model. So I presume it could be a workaround Einstein devised to avoid gravity :)