Galileo’s classic thought experiment, in which he envisions a cannonball falling through the Earth, has been doable as a scaled-down real experiment for decades. Yet it remains undone. The reasons for not filling this gap in our empirical knowledge of gravity have little to do with physics and a lot to do with sociology. The influences go back to humans’ primitive concepts of an unmoving Earth, whose modern incarnations are embodied by Albert Einstein’s “relativistic” principles. An imaginary alien (Rotonian) perspective is adopted, whereby these ancient Earthian predilections are all questioned. Even the (3 + 1)-dimensionality of space is questioned. When Rotonians visit an astronomical body for the first time, their instinctive belief in accelerometer readings leads them to a gravitational hypothesis (Space Generation Model) according to which matter is the source of space. They conceive the essence of gravity as the process whereby matter regenerates itself and creates new space. They conceive the process as the outward motion OF space into a fourth spatial dimension; matter is thus seen as an inexhaustible source of perpetual propulsion. It is this stationary motion that causes the curvature of spacetime. The hypothesis is developed in detail with respect to local physics and a chart is plotted for a more in depth application to cosmological issues, as promised for Part 2. It is repeatedly urged that, of much greater importance than discussing these issues, is the need to at last do Galileo’s experiment.