Monochrome Image Gallery

James Clark Maxwell with his demon

James Clark Maxwell and his demon, artwork. Maxwell (1831-1879) is best known for his laws of electromagnetism, which laid the foundations for modern physics. His "demon" was a thought experiment to question the Second Law of Thermodynamics: the entropy of a system tends to increase. This means that a hot region cannot draw heat from a colder region. Maxwell's demon is a being that can operate a door between a hot and cold gas, opening it to allow a fast-moving (hot) molecule to pass to the hot side, or a slow- moving one to pass to the cold side. This would violate the second law. However, as the demon requires energy to distinguish between fast and slow approaching molecules, and to operate the door, the entropy of the system increases anyway

© BILL SANDERSON/SCIENCE PHOTO LIBRARY

Eris and Dysnomia

Eris and Dysnomia. Artwork of the dwarf planet Eris, seen from its moon Dysnomia (lower right). Eris was formerly called 2003 UB313, and was nicknamed Xena by its discoverers, and its moon was nicknamed Gabrielle. Eris is thought to be around 3000 kilometres across, which is slightly larger than Pluto. It takes 560 years to orbit the Sun. Eris is the largest known member of the Kuiper Belt of rocky, icy bodies, including Pluto, that orbit the Sun beyond Neptune. The discovery was made from observations made in 2003 at the Palomar Observatory, USA, by Mike Brown, Chad Trujillo and David Rabinowitz, and announced in July 2005. Dysnomia was observed in September 2005

© DETLEV VAN RAVENSWAAY/SCIENCE PHOTO LIBRARY

cosmic ray atomic nuclei

Emulsion photograph showing the tracks of various cosmic ray nuclei, ranging from a hydrogen nucleus to an iron nucleus. The more protons a nucleus contains, the higher its positive electric charge & the greater its ability to ionise; the more it ionises, the denser its track in emulsion. Hydrog- en has 1 proton & produces a barely visible track. Ionisation depends on the square of the charge; so lithium's 3 protons have 9 times hydrogen's charge & produce a track 9 times denser. Iron, with 26 protons, produces a track 676 times denser than hydrogen. The wispy strands that adorn the denser tracks are "delta rays" - electrons knocked out of atoms in the emulsion by the passing nucleus

© POWELL FOWLER PERKINS/SCIENCE PHOTO LIBRARY