SpaceX is set to go public today, likely cementing founder Elon Musk — already the richest person in the world — a trillionaire .

Weighing heaily on people's minds ahead of SpaceX starting trading is Facebook's infamous debut in 2012.

SpaceX is expected to start trading on the ​Nasdaq for the first time later in the day and is likely to be immediately ranked as the seventh biggest publicly ​listed U.S. company, with a potential val...