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In Science, What Is Visibility?

Fog may effect visibility.
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  • Written By: J.M. Densing
  • Edited By: E. E. Hubbard
  • Last Modified Date: 08 April 2014
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In science, the term visibility refers to whether or not it is possible to see an object clearly, and the distance from which it can be seen. This is particularly relevant when discussing meteorology and astronomy. Visibility can be affected by a range of factors including weather, pollution, and time of day. These factors can change the condition of the atmosphere, altering the clarity of the air and affecting the ability to see objects, especially those that are far away.

The condition of the air is directly related to the ability to clearly see objects located in the distance. When the air is hazy or foggy, it is difficult to see distant objects clearly, but, when conditions are clear, it is much easier. This ability to see something distinctly and the distance from which this is possible is known as visibility. It's often measured as the distance from which an object can be clearly seen, stated in miles or kilometers.

Two of the scientific disciplines where visibility is particularly important are meteorology and astronomy. Many different weather phenomenon, such as fog, clouds, and humidity, can have a profound impact on the ability to see objects at a distance. The correlation is so significant that most weather reports include a measure of visibility. These measures are particularly relevant for astronomers, since they affect their ability to see celestial bodies, such planets or the Moon, and to study outer space.

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There are many factors, such as weather and pollution, that can have an effect on air clarity. Visibility is adversely affected by particles suspended in the atmosphere, like water vapor and pollutants. Miniscule droplets of water in water vapor reflect light, making it harder to see clearly through the air when looking at an object far away. This occurs when conditions are very humid, foggy, or cloudy, as well as during various types of precipitation such as drizzle or snow. Air pollution causes a similar effect from the toxins that are suspended in the air, which is called smog or haze, and the negative impact is magnified on days with humid conditions.

The time of day can also affect visibility due to the differing light conditions. It's generally difficult to see objects at a distance during times with partial darkness, such as twilight. Another factor that has an effect is the object being observed and the amount of contrast it has with its surroundings. For example, the Moon is not usually visible during the day when the sky is bright, but, at night, its visibility increases due to the contrast between the Moon's light and the surrounding darkness.

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