UPDATE: LAUNCH TIME CHANGED TO 2:05 pm.
Today SpaceX will attempt to launch the Falcon Heavy rocket Tuesday. This will be the first flight of the heaviest rocket currently in production. The rocket has three major pieces. Two smaller booster rockets are connected to a much larger core stage rocket. The two boosters will detach and return to a landing zone. SpaceX will attempt to land the boosters so they can be reused.
The main core rocket will continue and deliver its payload. The main rocket will then attempt to land to be reused.
The payload for this demo mission is Elon Musk's Tesla Roadster. SpaceX will attempt to put the car into an orbit around Mars. The car also has a mannequin named Starman riding in the drivers seat and David Bowie will be playing on the radio.
Simulation of the Falcon Heavy Demo Flight