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gnomon

Primary Information
Secondary Information

Definition

A gnomon is a pointer or indicator on a sundial. It is a triangular blade that casts a shadow on the sundial's face. The shadow's length and direction indicate the time of day.

The gnomon is named after the Greek word "gnomon," which means "indicator" or "one who discerns." The first sundials were made in Egypt around 3500 BC. They were simple devices, with a gnomon that was just a stick stuck in the ground.

As sundials became more sophisticated, the gnomon became more complex. The shape of the gnomon was often adjusted to compensate for the tilt of the Earth's axis. The length of the gnomon was also adjusted to account for the latitude of the location where the sundial was placed.

Gnomons are still used today in some parts of the world. They are also popular among hobbyists and collectors.

How can the word be used?

The astronomer used a gnomon to calculate the position of the sun.

gnomon

Different forms of the word

Noun: gnomon.

Adjective: gnomic.

Verb: to gnomonize.

Synonym: indicator, pointer.

Etymology

The word "gnomon" comes from the Greek word "γνώμων" (gnōmon), which means "indicator" or "pointer". The word was first used in English in the 16th century to refer to the rod or bar that is used to cast a shadow in order to tell time or measure the sun's altitude.

Question

What is a gnomon?

AQA Science Exam Question and Answer

Question:

What is a gnomon and how does it work?

Answer:

A gnomon is a rod or other object that is used to cast a shadow to tell the time of day or the position of the sun. It is typically placed in a sundial, which is a device that uses a gnomon to measure the passage of time.

The gnomon casts a shadow on a flat surface, such as a piece of paper or a sundial plate. The length of the shadow depends on the angle of the sun to the ground. At noon, when the sun is directly overhead, the shadow will be shortest. As the sun moves towards the horizon, the shadow will become longer. The position of the shadow can be used to tell the time of day.

For example, if the shadow is 6 inches long at noon, then it will be 12 inches long at 6:00 PM. This is because the sun will be 60 degrees from the zenith at 6:00 PM.

Gnomons can also be used to measure the position of the sun in the sky. For example, if the shadow is 45 degrees from the vertical at a certain time, then the sun is at an angle of 45 degrees to the horizon. This information can be used to determine the latitude of the location where the gnomon is placed.

Here are some additional points that could be included in the answer:

  • The gnomon was invented by the ancient Egyptians and was used for centuries to tell the time and to measure the position of the sun.
  • Gnomons are still used today in some parts of the world, such as in India and China.
  • Gnomons can be made from a variety of materials, such as wood, metal, or stone.
  • Gnomons are a simple and effective way to tell the time and to measure the position of the sun.