In Back to the Future, the scientist who invents the time machine is Doc Brown, whose full name is Dr. Emmett Lathrop Brown.
Doc Brown builds the time machine by converting a DMC DeLorean into a vehicle capable of traveling through time. Its crucial component is the flux capacitor, which he says makes time travel possible. In 1985, the DeLorean requires 1.21 gigawatts of electricity and initially uses stolen plutonium to generate the necessary energy.
The story says Doc first conceived the flux capacitor in November 1955 after slipping while hanging a clock in his bathroom. He struck his head and experienced a vision of the device. When Marty McFly accidentally travels back to 1955, he seeks out the younger Doc Brown, who helps him repair the DeLorean and restore the timeline.
Einstein is Doc's dog, not the inventor; Marty is the teenage traveler, not the scientist; and Biff Tannen is the trilogy's antagonist. Doc Brown is played by Christopher Lloyd in the original trilogy.