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

Consider a cask filled with a highly compressed gas. If we open one of its taps the gas will escape through it in a continuous flow, the elasticity of the gas pushing its particles into space will continuously push the cask itself. The result will a continuous change in the motion of the cask. Given a sufficient number of taps (say, six), we would be able to regulate the outflow of the gas as we liked and the cask (or sphere) would describe any curved line in accordance with any law of velocities.

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

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

The Earth is the cradle of Humanity. But one doesn't always live in the cradle.

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.