Accelerate a pool ball (or any object with mass) to near the speed of light. It will have greater mass.
That said, I think you have made your disdain for this poster's question loud and clear now several times.
Best,
KMRUNOUT
I have to laugh more and more at this. If we accept that the speed of light is 186,000 miles per second, that makes it way fast, when you convert to miles per hour. From an earlier pool article, I think the hardest breakers were in the 30 mile per hour range.
Therefore, I'm trying hard to find some connection to speed of light, and pool balls gaining weight, with your analysis. I can't find practical connection to the OP's theory.
Actually, I don't have disdain. I do question some theory where someone obviously has not used, nor has familiarity with, either calipers, or a scale.
That said, your level of relevance and sagacity is about par in this thread, where someone thought billiard balls gain weight. But I think he thought that in the real world. But then again, he may have been just trying to get reaction. Certainly did. Continues to be one of the more comical threads, fed suddenly by irrelevant and impossible theories.
All the best,
WW