fixed star

Thân thiện

A fixed star shines brightly in the night sky.

Definition

1. Noun:
   • A star that appears to maintain a constant position relative to other stars in the night sky: In historical astronomy, a "fixed star" is any star whose position in the celestial sphere seems unchanging over human timescales, as opposed to "wandering stars" (planets).
   • Specifically, a star in the Ptolemaic geocentric model: In the context of the Ptolemaic theory of planetary motion, a "fixed star" is any star embedded in the outermost celestial sphere, which was believed to rotate around a stationary Earth.

Usage Examples

• Noun:
  • Ancient astronomers catalogued the positions of many fixed stars.
  • In Ptolemy's system, the fixed stars formed a backdrop against which the planets moved.

Advanced Usage

• "Fixed star" in historical context: Used to discuss pre-Copernican astronomy.
  • The concept of the fixed star was fundamental to celestial navigation for centuries.
• Metaphorical use: Sometimes used poetically or metaphorically to describe something perceived as constant or unchanging.
  • Her principles were a fixed star in the shifting politics of the time.

Variants and Related Words

• Fixed (adj): Securely placed or fastened; stationary.
• Star (n): A luminous celestial body.
• Planet (n): In the historical context contrasted with a "fixed star," a "wandering star."
• Celestial sphere (n): An imaginary sphere of which the observer is the center, used in ancient and medieval astronomy.

Synonyms

• Background star (in historical/contrastive contexts).
• Non-wandering star (descriptive term).

Related Phrases

• Sphere of the fixed stars: The outermost rotating sphere in the Ptolemaic universe containing the fixed stars.
  • Ptolemy placed the sphere of the fixed stars beyond the spheres of the planets.

Notes on Meaning

• The term "fixed star" is primarily historical and scientific. In modern astronomy, all stars have proper motion, but their immense distances make this motion undetectable without precise instruments over long periods, so they are still effectively "fixed" for casual observation. The term highlights the historical distinction between the apparently motionless stars and the visibly moving planets.

Học thuật

Noun

1. any star in the Ptolemaic theory of planetary motion