Trajectories to other planets
Plot a real transfer from Earth to any planet, and see why you never aim at the target.
A spacecraft is never pointed at its destination. The trip takes months, the planet keeps moving, and you travel on a curved orbit around the Sun rather than a straight line — so you aim at empty space, well ahead of where the target is now.
This model plots real transfers from Earth to Mercury, Venus, Mars, Jupiter or Saturn using JPL’s planetary positions. Pick a departure date and it finds the cheapest route, draws the angle between where you point and where the planet is, and shows what the trip costs in speed.