SpaceX has gone public in a large stock market debut, but its valuation is uncertain, with some reports suggesting it may be worth less than half of its $1.75 trillion target. The company's stock performance is being closely watched, particularly after it was added to the Nasdaq-100, and some outlets are questioning its potential for long-term growth. The company's founder, who once expressed doubts about its survival, may become a trillionaire as a result of the IPO.