Nvidia just announced a $50 billion share buyback.On Aug. 28, Wall Street held its breath as the world's most important artificial intelligence (AI) company reported second-quarter earnings. I'm talking about Nvidia (NVDA -4.08%), of course. While each member of the "Magnificent Seven" is seen as an indicator for the direction of all things AI, Nvidia has emerged as perhaps the industry's end-all-be-all barometer.But fear not! Once again, Nvidia silenced the doubters after posting yet another spectacular ea ...