We came to conclusion, in
chapter 4.9, that the mass of the mass particle is proportional
to the flow of space into it. Admitting the existence of the flow of the
space into a singularity, we can explain the gravitational acceleration by means of this
flow, being accelerated on its way to the mass particle.

Travelling in a reference frame X together with its spacetime structure into the mass
particle M, situated in a reference frame M, the observer can detect the speed v_{m/x
} (or v_{xm
}, emphasizing that it is the galileian projection of the speed v_{x/m
}) of the mass particle M moving in a direction opposite to the speed
v_{x/m} of the frame X(or to the flow of the space) moving with reference to the mass
particle.

Fig.8 The spaceflow speed in a gravitational field

The spacetime density of the own frame (or, the frame intrinsic spacetime density) must be
detected the same in all reference frames, as discussed in
chapter 2.
Travelling together with the flow of space, the observer in frame X
detects the spaceflow as

(101)

(102)

where r_{x} stands for the
distance MX (between the gravitational singularity point M and the falling orbital area X), in units of the X frame,
as if the globe defined by
the centre point M and radius r_{x} was filled in by the space of constant space
density, the same as on the spherical area of the radius r_{x} ,
and Q stands for the flow of the space into a singularity M.

Fig.9 The spacetime structure falling into a singularity

Evidently must be Q = const, defined by a quantity of the mass in the mass point, if we
take spaceflow as the flow of the basic (preferred) reference frame spacetime structure,
because there is no reason to expect that the flow of the spacetime structure may increase, or
decrease on its way into singularity. In case, however, when Q is constant, the speed
v_{m/x}, representing the movement of the mass point with respect to frame X
-connected with spacetime structure, will have to be constant too, because change of speed
v_{m/x} would cause change of the flow of the space (see equation
(36)). Consequently,
the radius r_{x} must be constant too (see equation 101). This consequence,
ridiculous at first sight, can be explained very simply, by means of change of the space density,
as shown on Fig.9.

This is why we may say, that, travelling together with the spacetime structure into a mass
singularity, we are detecting constant speed v_{m/x}, constant
radius r_{x}, and, of course, constant spacetime density as well.