Definitions for speed of light
speed of light

Princeton's WordNetRate this definition:0.0 / 0 votes

1. speed of light, light speed, cnoun

   the speed at which light travels in a vacuum; the constancy and universality of the speed of light is recognized by defining it to be exactly 299,792,458 meters per second

WiktionaryRate this definition:0.0 / 0 votes

1. speed of lightnoun

   The speed of electromagnetic radiation in a perfect vacuum: exactly 299,792,458 metres per second by definition.

WikipediaRate this definition:0.0 / 0 votes

1. Speed of light

   The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour). According to the special theory of relativity, c is the upper limit for the speed at which conventional matter or energy (and thus any signal carrying information) can travel through space.All forms of electromagnetic radiation, including visible light, travel at the speed of light. For many practical purposes, light and other electromagnetic waves will appear to propagate instantaneously, but for long distances and very sensitive measurements, their finite speed has noticeable effects. Starlight viewed on Earth left the stars many years ago, allowing humans to study the history of the universe by viewing distant objects. When communicating with distant space probes, it can take minutes to hours for signals to travel from Earth to the spacecraft and vice versa. In computing, the speed of light fixes the ultimate minimum communication delay between computers, to computer memory, and within a CPU. The speed of light can be used in time of flight measurements to measure large distances to extremely high precision. Ole Rømer first demonstrated in 1676 that light travels at a finite speed (non-instantaneously) by studying the apparent motion of Jupiter's moon Io. Progressively more accurate measurements of its speed came over the following centuries. In a paper published in 1865, James Clerk Maxwell proposed that light was an electromagnetic wave and, therefore, travelled at speed c. In 1905, Albert Einstein postulated that the speed of light c with respect to any inertial frame of reference is a constant and is independent of the motion of the light source. He explored the consequences of that postulate by deriving the theory of relativity and, in doing so, showed that the parameter c had relevance outside of the context of light and electromagnetism. Massless particles and field perturbations, such as gravitational waves, also travel at speed c in vacuum. Such particles and waves travel at c regardless of the motion of the source or the inertial reference frame of the observer. Particles with nonzero rest mass can be accelerated to approach c but can never reach it, regardless of the frame of reference in which their speed is measured. In the special and general theories of relativity, c interrelates space and time and also appears in the famous equation of mass–energy equivalence, E = mc2.In some cases, objects or waves may appear to travel faster than light (e.g., phase velocities of waves, the appearance of certain high-speed astronomical objects, and particular quantum effects). The expansion of the universe is understood to exceed the speed of light beyond a certain boundary. The speed at which light propagates through transparent materials, such as glass or air, is less than c; similarly, the speed of electromagnetic waves in wire cables is slower than c. The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material (n = c/v). For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c/1.5 ≈ 200000 km/s (124000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.

WikidataRate this definition:0.0 / 0 votes

1. Speed of light

   The speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics. Its value is exactly 299,792,458 metres per second, a figure that is exact because the length of the metre is defined from this constant and the international standard for time. In imperial units this speed is approximately 186,282 miles per second. According to special relativity, c is the maximum speed at which all energy, matter, and information in the universe can travel. It is the speed at which all massless particles and associated fields travel in vacuum. It is also the speed of gravity predicted by current theories. Such particles and waves travel at c regardless of the motion of the source or the inertial frame of reference of the observer. In the theory of relativity, c interrelates space and time, and also appears in the famous equation of mass–energy equivalence E = mc². The speed at which light propagates through transparent materials, such as glass or air, is less than c. The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material. For example, for visible light the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200,000 km/s; the refractive index of air for visible light is 1.000293, so the speed of light in air is 299,705 km/s or about 88 km/s slower than c.

The New Hacker's DictionaryRate this definition:0.0 / 0 votes

1. speed of light

   The absolutely fastest a particular algorithm or application could be implemented, given a set of constraints that are assumed to be unchangeable. For example, “This would take 60 microseconds without any processing whatsoever, so that's the speed of light.” However, as one brilliant hacker once commented: “Remember that the speed of light only is constant if you can't redesign the universe.”

Editors ContributionRate this definition:0.0 / 0 votes

1. speed of light

   A known speed for light to travel.

   Speed of light is used in science and physics.

   
   

   Submitted by MaryC on January 22, 2021  

Matched Categories

1. • Constant
   • Speed

How to pronounce speed of light?

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How to say speed of light in sign language?

Numerology

1. Chaldean Numerology

   The numerical value of speed of light in Chaldean Numerology is: 2

2. Pythagorean Numerology

   The numerical value of speed of light in Pythagorean Numerology is: 9

Examples of speed of light in a Sentence

1. Eric Tennen:

   It's all happening at the speed of light, it's just crazy. I don't know what's what anymore.

2. Cale Hughes:

   It is throwing massive amounts of photons at an incoming object, we don't worry about wind, we don't worry about range, we don't worry about anything else. We're able to engage the targets at the speed of light.

3. Seth Berkley:

   We have to think about it as a disease. This is a disease, this spreads at the speed of light, literally.

4. Douglas Adams:

   Nothing travels faster than the speed of light with the possible exception of bad news, which obeys its own special laws.

5. Yonatan Winetraub:

   Landing is the most difficult part of the mission for multiple reasons, it takes radio signals traveling at the speed of light 2 to 3 seconds in total to send and receive messages – the spacecraft is traveling at 2 kilometers a second at that point.

References

1. ^ Princeton's WordNet
   http://wordnetweb.princeton.edu/perl/webwn?s=speed of light
2. ^ Wiktionary
   https://en.wiktionary.org/wiki/Speed_of_Light
3. ^ Wikipedia
   https://en.wikipedia.org/wiki/Speed_of_Light
4. ^ Wikidata
   https://www.wikidata.org/w/index.php?search=speed of light
5. ^ The New Hacker's Dictionary
   https://www.gutenberg.org/files/3008/3008-h/3008-h.htm#SpeedofLight