In the 1968 film adaptation of the science fiction classic "2001: A Space Odyssey" by Stanley Kubrick, the spaceship Discovery takes a mere five months to travel from Earth to the planet Jupiter. This is an astonishingly short time for the five-man crew and the quirky onboard computer HAL. However, reality tells a different story. The NASA probe Galileo, launched in 1989, took six years to reach Jupiter. The small spacecraft had to gain momentum by swinging past Venus once and Earth twice. Only after these three flybys, which took three years, did Galileo accumulate enough kinetic energy to make the leap to Jupiter, a journey that took an additional three years. Why does humanity hit such limits in space travel so quickly?.