speed of light: meaning, definition, pronunciation and examples
C1Technical, Scientific, Figurative
Quick answer
What does “speed of light” mean?
The constant speed at which light travels in a vacuum, approximately 299,792,458 metres per second.
Audio
Pronunciation
Definition
Meaning and Definition
The constant speed at which light travels in a vacuum, approximately 299,792,458 metres per second.
Used metaphorically to describe something that is extremely fast or instantaneous.
Dialectal Variation
British vs American Usage
Differences
No significant lexical differences. The concept is identical in both varieties.
Connotations
Identical scientific and figurative connotations.
Frequency
Equally common in technical/scientific contexts. Figurative use is slightly more common in American media/colloquial speech.
Grammar
How to Use “speed of light” in a Sentence
[Verb] at the speed of light[Adjective] than the speed of lightThe speed of light [Verb]Vocabulary
Collocations
Examples
Examples of “speed of light” in a Sentence
verb
British English
- Information seems to speed-of-light around the internet these days.
American English
- The rumor speed-of-lighted through the school before first period.
adverb
British English
- The data transferred speed-of-light between the servers.
American English
- He finished the task speed-of-light and moved on to the next.
adjective
British English
- We need speed-of-light processing for this real-time analysis.
American English
- The company promised speed-of-light delivery for its premium service.
Usage
Meaning in Context
Business
Rare. Used hyperbolically: 'Our new data processing happens at the speed of light.'
Academic
Common in physics, astronomy, and engineering contexts to denote the constant c.
Everyday
Figurative use: 'News travels at the speed of light on social media.'
Technical
The precise term for the fundamental physical constant, central to relativity.
Vocabulary
Synonyms of “speed of light”
Strong
Neutral
Weak
Vocabulary
Antonyms of “speed of light”
Watch out
Common Mistakes When Using “speed of light”
- Using 'speed of the light' (incorrect addition of definite article).
- Confusing 'speed of light' (noun phrase) with 'light-speed' (often adjectival).
FAQ
Frequently Asked Questions
Yes, in the vacuum of space, it is a fundamental physical constant, denoted by 'c', and does not change.
According to our current understanding of physics (Einstein's theory of relativity), no object with mass can reach or exceed the speed of light.
It is now defined as exactly 299,792,458 metres per second. Historically, it was measured using precise astronomical observations and later laboratory experiments like rotating mirrors.
It is a cornerstone of modern physics, crucial to Einstein's theory of relativity, and defines the relationship between space and time. It also sets the ultimate speed limit for the transfer of information in the universe.
The constant speed at which light travels in a vacuum, approximately 299,792,458 metres per second.
Speed of light is usually technical, scientific, figurative in register.
Speed of light: in British English it is pronounced /ˌspiːd əv ˈlaɪt/, and in American English it is pronounced /ˌspid əv ˈlaɪt/. Tap the audio buttons above to hear it.
Phrases
Idioms & Phrases
- “at the speed of light”
- “faster than the speed of light”
Learning
Memory Aids
Mnemonic
Think: 'Light is the fastest thing we know. Nothing can go faster, so it's the ultimate speed.'
Conceptual Metaphor
ULTIMATE SPEED IS THE SPEED OF LIGHT (e.g., 'He ran at the speed of light').
Practice
Quiz
What is the most common figurative meaning of 'at the speed of light'?