"But this does not account for the continuance of motion once started.
"Inertia says a body will move once started, but it doesn't say why or how. How does that particle once started gain the knowledge to continue without some direct control over its spatial framework? That it will continue, we know. That in the presence of a gravitic field or a magnetic field or other attractive force at right angles to its motion, we can create an acceleration which will maintain it in an exactly circular path called an orbit. But how does it remember, as soon as that field ceases to exist, where it was going before it was last influenced? That it will continue in a straight line indefinitely, without such an influence, we know. That it can be influenced over a distance by various field effects, we also know. But what is the mechanism of influence whereby it influences itself to continue in a straight line? And what handle did we get hold of to convert that influence of self to our own advantage in moving this ship?"
"I thought you physics boys did it all with math," he said softly, "and here you've outlined the facts of space that an Indian can feel in his bones--and you've done it in good, solid English that makes some sense.
"In other words," Mike was almost talking to himself as he tried to reword Ishie's theorizing into his own type of thinking, "the particle in motion creates a strain in the fabric--the field--of space; and that fabric must attempt to relieve itself of the strain. A particle in motion makes it possible for the fabric of space to smooth itself out behind the particle; and the fabric attempts to smooth itself on through the area occupied by the particle while it is moving, and so the fabric of space smoothing itself is a constant thrust behind the particle's motion, continuing that motion and making the particle scat to where he wasn't going.
"When that same particle is stopped," Mike was visualizing the process to himself, "the force of the attempt to smooth itself out by the fabric of space exists equally around the particle on all sides; so that the particle will be held stopped by the attempt of the fabric to smooth itself until set into motion again by a force greater than that of inertia--for inertia, then, is the attempt of the fabric of space to smooth itself.