Le ciel est, par-dessus le toit, The sky is, up above the roof, Si bleu, si calme! So blue, so calm! Un arbre, par-dessus Je toit, A tree there, up above the roof, Berce sa palme. Waves leaves of palm. La cloche, dans le ciel qu'on voit, A church bell, in the sky I see, Doucement tinte. Softly tolls. Un oiseau, sur l'arbre qu'on voit, A bird, upon the tree I see, Chante sa plainte. Sadly calls. PAUL VERLAINE Like Verlaine, we are in prison. The prison is our Earth, "which is so pretty"; our atmosphere and its clouds, its "marvellous clouds". (You would think that Verlaine, Prevert and Baudelaire had been comparing notes!) The sky is up above the roof... A tree there, up above the roof... Stars in the sky, like birds ... their rays, like bells (and here we are with Apollinaire!) What we see opens the way to what we guess at; what we observe Ieads us towards the unobservable. A poem releases images, and the invisible grows big with reality. Astronomcrs are a little like poets (indirectly from the Greek 7tostco, make): they make the universe by interpreting messages, extrapolating spectra, and inventing 'models' of the cosmos or of stars - fictional constructions whose observable part constitutes only a small fraction of the whole, and which only the inductive logic of the theoretician allows us to consider as representing unique physical reality.

Inhalt
I / The Raisons D'être of Space Astronomy.- I The structure of the Atmospheric Layers.- II The Opaque Wall of the Atmosphere.- III Atmospheric Diffusion: Extinction and the Blue of the Sky.- IV The Inhomogeneity of the Earth's Atmosphere: Clouds and Refraction.- V The Particle Barrier.- VI The Fusion of Meteorites.- II / A Provisional and Partial Inventory of Some of the Information to be Acquired by Space Research.- I Beyond Diffusion.- II Beyond Turbulence.- III Beyond Ultraviolet Opacity.- IV Astronomy at Short Wavelengths.- V Beyond Infrared Opacity: Towards the Infrared by Balloon.- VI Beyond the Ionosphere: Towards Very Long Wavelengths by Eccentric Satellite.- VII A Prospective Conclusion of Limited Perspective.- Conclusion.- I. Universal Physical Constants.- II. The Sun.- III. The Solar System.