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Articles About Earth (18)

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. more

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? more

March Equinox

The March equinox around March 20-21 is the spring (vernal) equinox in the Northern Hemisphere and fall (autumnal) in the south. Night and day are nearly the same length. more

June Solstice

The June solstice is the longest day of the year in the Northern Hemisphere & the shortest day in the Southern Hemisphere. more

September Equinox

The Sun shines directly at the Equator on the September equinox and the length of day and night is nearly equal, but not quite. more

December Solstice

The December solstice is also known as the summer solstice in the Southern Hemisphere and the winter solstice in the Northern Hemisphere. more

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. more

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. more

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? more

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. more

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. more

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? more

What Causes Seasons?

Seasons change because Earth's rotational axis tilts away or towards the Sun during the course of a year. more

What Causes Tides?

The combined gravitational force of the Moon and the Sun causes the tides in Earth's oceans. There are 2 high tides and 2 low tides every 24 hours and 50 minutes (lunar day). more

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