we can physically observe it in all and every planetary and galactic motion in the Universe, every star and every black hole
Really? How you could phisically observe all that? As far as I know, you read lectures of gases, expectrum of light and things like that, you do not actually see any of this stuff, phisically talking (with your eyes), btw I could argue that "gravity force" is just a difference in density but ...
Of the four fundamental forces, this is the only force without an opposite
If you want to go against the 3rd law of Newton that say for any action will be a reaction with the same force maybe ...
Also I can ask about the artifcial horizont in planes, how ships navegate, or the point of view of the plane pilots, how limited our vision works, and some others thing ... honestly I do not care if the earth is flat, or round or a disc, it does not make any difference to my life actually but I preffer to believe in my senses and not in what someone with a paper who say he is scientist tell me I have to believe withou questioning ... looks a lot to religion in that way and I am not a religiuos man
Btw, sorry for may bad writted english
Pd: any time I see people loosing time with this kind of theme that does not bring anything to humanity, just division ... I have to intervine, sorry about that.