A K Raychaudhuri and his equation

J EHLERS

Max-Planck-Institute for Gravitational Physics, Albert-Einstein-Insitute,

Am M\"uhlenberg 1, D-14476 Golm, Germany

E-mail: juergen.ehlers@aei.mpg.de

Abstract. Amal Kumar Raychaudhuri died on June 18, 2005. This essay

follows the lecture which I gave in honour of this great Indian scientist

and teacher on December 26, 2005 in Puri, India.

Keywords. Raychaudhuri equation; cosmology; gravitational collapse.

PACS Nos 01.60; 98.80