A clipart illustration by Phillip Martin titled "Observation."

An image of "Annunciation and Nativity (Altarpiece of Observation)", created by Francesco Del Cossa in 1470 (Tempera on panel, 137 x 113 cm, and 26,5 x 114,5 cm).

An image of "Brunhilde Observing Gunther, Whom She Has Tied to the Ceiling", created by John Henry Fuseli in 1807 (Pencil, pen and ink and wash, 483 x 317 mm).

An image of "The Observant Friars in the Refectory", created by Alessandro Magnasco from 1736-37 (Oil on canvas).

An image of "Napoleon and Pitt Observing Each Other", created by Piercy Roberts, c. 1809 (Coloured engraving).

Details of Mir's re-entry into the Earth's atmosphere after 15 years in space. Includes information on Mir's mission, configuration, and history.

Galileo Galilei (15 February 1564 - 8 January 1642) was a Tuscan (Italian) physicist, mathematician, astronomer, and philosopher who played a major role in the scientific revolution. His achievements include improvements to the telescope...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

The Jantar Mantar, in Jaipur, is an astronomical observation site built in the early 18th century. It includes a set of some 20 main fixed instruments. They are monumental examples in masonry of known instruments but which in many cases...

This site from NASA allows one to read the reports by scientists of what we learned from observing the giant collision of Comet Shoemaker-Levy 9 with Jupiter. Some are very technical, others for general audiences.

Images and data from the Hale Telescope of the collision of Jupiter and Comet Shoemaker-Levy 9. Some of the most excellent ground-based observations of the impact.

Images and data from the Hale Telescope of the collision of Jupiter and Comet Shoemaker-Levy 9. Some of the most excellent ground-based observations of the impact.

Arizona State's descriptions of the horn are broken up by illustrations of the horn, players, and music. There is a big discussion of crooks (not the kind that go to jail), but the kind that are made when you bend metal! The author notes...

Arizona State's descriptions of the horn are broken up by illustrations of the horn, players, and music. There is a big discussion of crooks (not the kind that go to jail), but the kind that are made when you bend metal! The author notes...

A discussion of entropy that focuses on explaining entropy, how it applies to the second law of thermodynamics, and real-life observations of the existence of entropy.

A discussion of entropy that focuses on explaining entropy, how it applies to the second law of thermodynamics, and real-life observations of the existence of entropy.

A discussion of entropy that focuses on explaining entropy, how it applies to the second law of thermodynamics, and real-life observations of the existence of entropy.