Will Apple save Rivian stock? (And what if it doesn't?)Rivian Automotive (RIVN -0.14%) stock soared more than 8% in early trading on the Nasdaq this morning. (Hurray!)Then its stock turned tail, gave back most of its gains, and as of 10:30 a.m. ET, it was up only 1.6%. (Boo!)Why did Rivian stock rise and then fall back again? The answer is just one word: Apple (AAPL 0.05%).Rivian and Apple: A match made in heaven? (Or perhaps Detroit?)So, here's the big news today about electric truck company Rivian and tec ...