Then wouldn’t Relativity tacitly support the notion of contra-gravity where the large mass is perceived to be moving towards the smaller mass? I would expect gravity not to be a quality/dimension of Relativity, but this topic is many decades old in my distant memory. All I recall is man walking inside a train that’s passing a platform — or something like that.
“Then wouldn’t Relativity tacitly support the notion of contra-gravity where the large mass is perceived to be moving towards the smaller mass?”
No, because both masses are still attracting each other, so it’s just gravity, whether you look at it from a reference of you falling towards the earth or the earth falling towards you.
“All I recall is man walking inside a train that’s passing a platform — or something like that.”
The basic idea is that the laws of physics remain the same no matter what frame of reference you choose to view things from. So if there is no anti-gravity in one reference frame, there can’t be anti-gravity simply created as an effect of switching to another reference frame.