Articles About Earth (20)
Earth Is Tilted
When an object the size of Mars crashed into the newly formed planet Earth around 4.5 billion years ago, it knocked it over and left it tilted at an angle.
Magnetic Declination
A compass needle doesn't point to the geographical North Pole but to magnetic north. Did you know that it usually doesn't point to the magnetic North Pole either?
March Equinox
March equinox marks the beginning of spring in the Northern Hemisphere. It is the Southern Hemisphere's autumnal/fall equinox.
June Solstice
The June solstice is the longest day of the year in the Northern Hemisphere & the shortest day in the Southern Hemisphere.
September Equinox
The Sun shines directly on the Equator on the September equinox and the length of day and night is nearly equal, but not quite.
December Solstice
The December solstice is the summer solstice in the Southern Hemisphere and the winter solstice in the Northern Hemisphere.
What Are Longitudes and Latitudes?
Cartographers and geographers divide the Earth into longitudes and latitudes in order to locate points on the globe.
What Causes Seasons on Earth?
Seasons change because Earth's rotational axis tilts away or towards the Sun during the course of a year.
What Causes Tides?
The gravitational pull of the Moon and the Sun makes the water in the oceans bulge, causing a continuous change between high and low tide.
Equation of Time
Why doesn't the year's earliest sunset occur on the winter solstice, even though it is the shortest day of the year in terms of daylight?
Astronomical Glossary - Terms & Definitions
What do astronomers really mean when they use those technical terms?
How Long Is a Day on Earth?
In terms of solar time, most days are a little longer than 24 hours. Exact day length for today and yesterday.
What Is the Umbra?
The umbra is the dark center portion of a shadow. The Moon's umbra causes total solar eclipses, and the Earth's umbra is involved in total and partial lunar eclipses.
Altitude & Azimuth: The Horizontal Coordinate System
Learn how to use altitude (elevation) and azimuth angles to locate any object in the sky, such as stars, planets, satellites, the Sun, or the Moon.
Is the Greenwich Meridian in the Wrong Place?
Why does a GPS device not show 0 degrees of longitude at the line marking the prime meridian in Greenwich, London, UK? Is it wrong—or just different?
Why 3 Shadows?
The Earth and the Moon cast 3 different shadows: umbra, penumbra, and antumbra. Why are there 3 types of shadows and how are they defined?
The Future of Leap Seconds
Organizations and individuals have for many years argued about abolishing leap seconds for good.
What Is the Penumbra?
The penumbra is the lighter outer part of a shadow. The Moon's penumbra causes partial solar eclipses, and the Earth's penumbra is involved in penumbral lunar eclipses.
What Is the Antumbra?
The antumbra is the lighter part of a shadow that forms at a certain distance from the object casting the shadow. It is involved in annular solar eclipses and planet transits.
What Is Earthshine?
Earthshine is a dull glow that occurs when the Sun’s light reflects off the Earth's surface and illuminates the unlit portion of the Moon.