ngày vũ trụ
Definition
- Noun:
- Sidereal day: The precise astronomical definition of "ngày vũ trụ" is the time it takes for the Earth to complete one full rotation on its axis relative to the distant, fixed stars. This period is approximately 23 hours, 56 minutes, and 4 seconds.
Usage Examples
- Noun:
- Một ngày vũ trụ ngắn hơn một ngày Mặt Trời mà chúng ta sử dụng hàng ngày. (A sidereal day is shorter than the solar day we use in daily life.)
- Các nhà thiên văn học sử dụng ngày vũ trụ để quan sát các vì sao. (Astronomers use the sidereal day to observe the stars.)
Advanced Usage
- The term "ngày vũ trụ" is highly specialized and used almost exclusively in the context of astronomy and astrophysics. It is a precise measurement for celestial observation and satellite tracking, not for civil timekeeping.
Variants and Related Words
- Ngày Mặt Trời (n): Solar day. The basis for civil time, measured relative to the Sun (approximately 24 hours).
- Ngày sao (n): Another, less common Vietnamese term for sidereal day, synonymous with "ngày vũ trụ".
Synonyms
- Sidereal day: The direct and precise English equivalent.
Notes on Meaning
- Important Distinction: Do not confuse "ngày vũ trụ" (sidereal day) with a general "day in space" or "cosmic day." Its meaning is specific to the Earth's rotational period measured against the fixed stellar background. It is not a calendar day used in space travel.