The first human use of the wind to power boats most likely occurred in about 3,000 BC. This was a major improvement in travel over walking and animal drawn carts. Three or four hundred years from now humans may send a robotic space probe to a nearby star using a light sail as big as the state of Texas. Ideally it would deploy its giant solar sail near the Sun perhaps as close to it as the planet Mercury. This would give it maximum initial thrust. After it gets far from the Sun it could be pushed along by a powerful pinpoint laser beam. Theoretically it is possible to achieve a fraction of the speed of light through this means.