The Millennium that Defined Earth
31.12.2000

When the second millennium began, people generally knew that the Earth was round, but few saw much of it beyond their local village. As the millennium progressed, humans mapped the continents, circumnavigated the globe, and determined the composition of the Earth.

Galileo Demonstrates the Telescope
13.09.1998

Galileo Galilei made a good discovery great. Upon hearing at age 40 that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted his own telescope and turned it toward the sky.

A Mercury Transit Sequence
27.05.2003

Earlier this month, the planet Mercury crossed the face of the Sun, as seen from Earth. Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun.

The Ecliptic Plane
27.09.1997

The Plane of the Ecliptic is illustrated in this Clementine star tracker camera image which reveals (from right to left) the Moon lit by Earthshine, the Sun's corona rising over the Moon's dark limb, and the planets Saturn, Mars, and Mercury.

Goa Silhouettes
22.03.2007

On Moonday, March 19, shortly before the equinox, locations in Asia and the Arctic were favoured by the New Moon's shadow during a partial solar eclipse. Although the view from Goa, India found...

Uranus' Moon Miranda
24.12.1995

NASA's robot spacecraft Voyager 2 passed the planet Uranus and its moons in 1986. While the cloud tops of Uranus proved to be rather featureless, the surface of Miranda, the innermost of Uranus' large moons, showed several interesting features.

Galileo Demonstrates the Telescope
30.08.1996

Galileo Galilei made a good discovery great. Upon hearing at age 40 that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted his own telescope and turned it toward the sky.

A Halo Around the Moon
21.04.2003

Have you ever seen a halo around the Moon? This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. Each ice crystal acts like a miniature lens.

The Ecliptic Plane
29.05.1999

The Plane of the Ecliptic is illustrated in this Clementine star tracker camera image which reveals (from right to left) the Moon lit by Earthshine, the Sun's corona rising over the Moon's dark limb, and the planets Saturn, Mars, and Mercury.

Venus on the Horizon
19.06.1999

Venus can appear as a brilliant evening star. Besides the sun and moon, Venus is the brightest object visible in Earth's sky. Because it is closer to the sun than Earth, Venus never...