Man must at all costs overcome the Earth's gravity and have, in reserve, the space at least of the Solar System. All kinds of danger wait for him on the Earth. . . . We have said a great deal about the advantages of migration into space, but not all can be said or even imagined.

First, inevitably, the idea, the fantasy, the fairy tale. Then, scientific calculation. Ultimately, fulfillment crowns the dream.

A planet is the cradle of mind, but one cannot live in a cradle forever.

Man must at all costs overcome the Earth's gravity and have, in reserve, the space at least of the Solar System.

Man must at all costs overcome the Earth's gravity and have, in reserve, the space at least of the Solar System. All kinds of danger wait for him on the Earth. . . . We have said a great deal about the advantages of migration into space, but not all can be said or even imagined.

Men are weak now, and yet they transform the Earth's surface. In millions of years their might will increase to the extent that they will change the surface of the Earth, its oceans, the atmosphere, and themselves. They will control the climate and the Solar System just as they control the Earth. They will travel beyond the limits of our planetary system; they will reach other Suns, and use their fresh energy instead of the energy of their dying luminary.

All our knowledge - past, present, and future - is nothing compared to what we will never know.