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Glite Dictionary
light second

light second

6.7
The distance light travels in one second in empty space, about 300,000 kilometers
  • noun
  • /laɪt ˈsɛkənd/
  • Specialized
translation icon : segundo luz
  • If the object were a hundred light-seconds away, you'd only have a second to respond.
  • light seconds away
  • two light seconds

It goes one light second per second, right?

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Examples

  • It goes one light second per second, right?

    Stanford

  • Earth is 0.04 light-seconds across.

    Academic text (2005)

  • If I'm going to use seconds for time, I use light seconds for distance, and then light rays.

  • Atop that, everyone knew that they were within light-seconds of billions of humans!

    Fiction book (2001)

  • You sit down right here, we'll have an antigrav here in a light-second. " p127

    Fiction book (1992)

  • His battles had been fought across light-seconds, with grasers and lasers and nuclear warheads, and for all that he knew, his personnel respected and trusted him; they did not idolize him.

    Fiction book (2001)

  • The nearest star is about four light seconds away from Earth.

  • A spacecraft can travel several light seconds away in just a few minutes.

  • When observing distant galaxies, we often measure their distance in light seconds.

How Far

light-year
  • Specialized
109 4.9
light time
  • Specialized
8.6
light hour
  • Specialized
8.1
light minute
  • Specialized
1 8.1
light second
  • Specialized
6.7

Surface Forms

light second singular
light seconds plural

Morphology

light + second

The constituents 'light' and 'second' signal something to do with light and the duration of one second, so the phrase points toward the distance light covers in that time; however, because 'second' is primarily a time unit, interpreting the compound as a unit of distance (rather than a time interval) depends on technical/scientific knowledge (and analogy with units like 'light-year'). This compositional, domain-specific mapping is partially clear but not immediately predictable for an average B1 learner, so it is semi-transparent.

Etymology

Light second comes from a simple idea: it is the distance light travels in one second, about 300,000 kilometres. Because light moves so fast, people use light seconds to talk about 'distance' in space and how long a signal will take, so if something is three light seconds away a radio or light signal takes about three seconds to get there.