Within special relativity criteria one finds that sort of comparative relationship of time and mass seeming to increase for slower objects compared to those travelling near light speed I suppose. I wonder though if mass moving nearly light speed through various fields-even virtual fields, doesn’t encounter resistance that seems like virtual mass gain even with characteristics of increased mass phenomenally. I think of general relativity and gravity changing spatial shape even to the point of bending the path of photons travelling around stars.
For some reason I have thought that Einstein intended to mean that significant mass accelerating nearly to space time would itself encounter ‘headwinds’ of field resistance comparable to that of a bicyclist riding faster into a headwind experiencing increased resistance. If gravity is a field, or if space and virtual particles have mass, an object passing close to the speed of light might in some way experience concatenated effects. I thought that is why there aren’t asteroids travelling at the speed of light though a nova or some such might explode at a very fast speed and accelerate such large objects. I don’t know of any large objects that travel at the speed of light, except some rotating black holes. Since they have so much gravity anyway (apparently there is no limit to the intensity of a gravitational field – it only need collapse spacing of mass) it seems reasonable that they can spin nearly at the speed of light.