Definition

1. Noun:
   • The apparent shift in the position of a celestial object when observed from two different points on Earth's surface, caused by Earth's rotation. This is a specific type of parallax used in astronomy. It measures the angle of displacement for a nearby celestial body (like the Moon or a planet) by observing it from two separate locations on Earth at the same time, or from one location as Earth rotates.

Usage

• Noun:
  • Astronomers calculated the Moon's distance using geocentric parallax by making simultaneous observations from observatories in different hemispheres.
  • The geocentric parallax of Mars is much smaller than that of the Moon because Mars is farther away.

Advanced Usage

• "Diurnal parallax": This is another term for geocentric parallax, emphasizing that the measurement is taken over the course of a day (diurnal cycle) due to Earth's rotation.
  • The diurnal parallax of an asteroid can be used to determine its orbit.

Variants and Related Words

• Parallax (n): The general effect or method of determining distance by observing an object from two different viewpoints.
  • Stellar parallax is used to measure the distance to nearby stars.
• Horizontal parallax (n): A specific measurement of geocentric parallax when the celestial body is on the observer's horizon.
  • The horizontal parallax is the maximum value of geocentric parallax for a given body.

Synonyms

• Diurnal parallax: The apparent shift measured over a daily cycle.

Related Concepts

• Heliocentric parallax: Parallax measured using two points in Earth's orbit around the Sun (annual parallax), used for measuring stellar distances.
• Triangulation: The geometric method underlying the concept of parallax for distance measurement.

Noun

1. the parallax of a celestial body using two points on the surface of the earth as the earth rotates