Images Dated 20th February 2004

Hummingbirds, historical artwork

Hummingbirds. 19th Century illustration of five different species of male hummingbird. There are approximately 340 species of hummingbird (family Trochilidae). They get their name from the characteristic hum of their rapid wing flapping, which allows them to hover in mid-air. They feed on nectar and are particularly attracted to red flowers. Illustration from Gems of Nature and Art

© SHEILA TERRY/SCIENCE PHOTO LIBRARY

Computer artwork of UFOs in an astronauts visor

Astronaut looking at UFOs. Computer artwork of an astronaut during a spacewalk looking at UFOs (unidentified flying objects). They are seen reflected in his visor. These UFOs take the form of "flying saucers". Some people believe that such objects are spacecraft carrying aliens which observe and even abduct humans. Sightings of UFOs are common, but most have a simple explanation. High clouds, weather balloons, aircraft and even the Moon have all been mistaken for alien craft. There are a few UFO sightings which have had no explanation

© VICTOR HABBICK VISIONS/SCIENCE PHOTO LIBRARY

Coloured SEM of the join between a tooth and crown

Dental crown. Coloured scanning electron microgr- aph (SEM) of the join between a tooth (green) and a dental crown (light blue). The tooth and ceramic crown are coated in debris (orange) which became attached to the tooth when it was extracted for this SEM. If the top of a tooth is badly cracked, decayed or broken, it must be replaced by an artificial crown. The remaining undamaged part of the tooth is cut down to a peg to receive the hollow crown. This crown is then shaped to form a replica of the original tooth and cemented in place. Here, the crack between the tooth and crown allows bacteria to enter and cause secondary tooth decay. Magnification: x50 at 6x7cm size

© VOLKER STEGER/SCIENCE PHOTO LIBRARY