Exceptionally Deep View of NGC 4921

Yet another amazing video created from images taken by the NASA/ESA Hubble Space Telescope. The video reveals lots of new details of the galaxy, as well as a rich background of remote galaxies stretching back to the early Universe.

3D animation of galaxies

This video was produced by Frank Summers, currently working as an astronomer for NASA. This animation of galaxies from the Hubble Space Telescope shows galaxies distributed over 10 billion years of cosmic time.

Einstein’s own popular book on relativity

The present book is intended as far as is possible to give an exact insight into the theory of Relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but are not conversant with the mathematical apparatus of theoretical physics.
Albert Einstein, from the preface.

Read the book online or download it.

Relativity: the Special and General Theory was written in 1916. This is a revised edition from 1924.

Grinstead and Snell's Introduction to Probability

This excellent introductory probability book is now available for free download in pdf format. It has been licensed under the terms of the GNU Free Documentation License: it is freely redistributable, and you can do whatever you like with the text, as long as you don't prevent anyone else from doing the same.

This book was written for an introductory probability course taken by sophomores, juniors, and seniors in mathematics, physical sciences, computer science, and engineering. It gives a thorough treatment of probability ideas and techniques necessary for a firm understanding of the subject.

Animal Evolution: Phanerozoic Eon

The Phanerozoic Eon is the eon in which we live, the one during which abundant animal life has existed. I've just found this amazing video on YouTube, it shows the evolution of fish, amphibians, reptiles, dinosaurs, mammals, and primates, starting more than 500,000,000 years ago, and ending today.