Alice and Oliver like sitting on the balcony and looking at the sky. They know that the Earth is a very welcoming planet, so much so that it is the only planet in the solar system on which there is life! But like all the other humans interested in the sky, they would love to be able to travel aboard a spaceship going to Mercury, Venus, Pluto... and beyond our solar system. Humans have always been curious to discover what things are like, both those in our planet and extraterrestrial things, which are things from outside the Earth!