Horizon

A colorful view of airglow layers at Earth's horizon

Sailing Boat Horizon

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Horizons

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Horizon

A horizon is the apparent line that separates the Earth from the sky. It is the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not. The true horizon is actually a theoretical line, which can only be observed when it lies on the same plane as the observer's eyes.

Types of Horizons

There are several types of horizons, including:

• True Horizon: The line that would be seen if there were no obstructions such as buildings, trees, or mountains.
• Apparent Horizon: The line that is visible to the observer, which may be obstructed by natural or man-made objects.
• Sea Horizon: The line where the sea surface appears to meet the sky.
• Astronomical Horizon: The great circle on the celestial sphere whose plane passes through the center of the Earth and is parallel to the observer's horizon.

Factors Affecting the Horizon

Several factors can affect the appearance and position of the horizon:

• Altitude: The higher the observer's altitude, the further away the horizon appears.
• Refraction: The bending of light as it passes through the Earth's atmosphere can cause the horizon to appear slightly higher than it actually is.
• Obstructions: Natural and man-made objects can obstruct the view of the true horizon, creating an apparent horizon.

Horizon in Different Contexts

The concept of the horizon is used in various fields:

• In astronomy, the horizon is used to define the position of celestial objects.
• In navigation, the horizon is crucial for determining the observer's position and for celestial navigation.
• In photography, the horizon is an important element in composition, often used to create a sense of balance and perspective.

Horizon in Culture

The horizon has significant cultural and symbolic meanings in various societies. It often represents the boundary between the known and the unknown, the attainable and the unattainable, or the beginning of a journey.

See Also

• Skyline
• Celestial sphere
• Altitude
• Refraction
• Navigation
• Photography