The concave earth or flat to our perception is a created cell of cells, probably among similar cells outside of it.
To us, the earth is our mother cell that houses us as a mass of small cells and everything else inside of it ranging in size.
How it all came about will probably never be known by our primitive minds, as in simply appearing.
Just as the cells that make the sperm that swim through other cells to penetrate a cell containing cells that contain cells which produce an organism made up of all those cells.
We are just a growing egg and we as cells are dying to be replaced just like the cells of our own bodies do.
Edit:
Nothing to do with this thread.
I know that this is a complex subject and is not easy to explain in ordinary language.
If a photon travels from A to B in a straight line, it will take x amount of time. If the same photon travels from the same A to B but in a curve will it take the photon a longer time than the staight x amount of time. Or a massive object slows down time but the photon travels at the same speed.
1. Yes, longer distance = longer time.
2. I'm not sure what you are asking here but massive objects will not slow light, but they will change the wavelength. See gravitational lensing.