# What is the speed of light? (Definition, facts)

The speed of light is approximately **299,792.458 kilometers per second km/s**. This is considered to be the fastest speed at which anything can travel in the universe. It is also the speed at which light travels in a vacuum.

## Speed Of Light Definition (Costant)

The speed of light is a fundamental physical constant that represents **the speed at which light travels in a vacuum**. It is denoted by the symbol "c" and is approximately 299,792,458 meters per second (m/s) or 299,792.458 kilometers per second km/s. This speed is considered to be the fastest speed at which anything can travel in the universe. It is an important concept in physics, as it is used in the development of many scientific theories, including those in the fields of optics, electromagnetism, and relativity. The speed of light is considered to be an "invariant" speed, meaning that it is the same for all observers regardless of their relative motion.

### The Speed Of Light Equation

The speed of light is a fundamental physical constant, and as such, it does **not have a specific equation**. It is simply a constant value that is used in various equations and formulas in physics.

In some equations, the speed of light is used as a conversion factor between the units of distance and time. **For example**, **the distance that light travels in one year is approximately 9.461 x 10^15 meters (9.461 petameters or 9.461 Pm)**. This is often used in astronomical calculations.

In other equations, the speed of light is used to calculate the energy or frequency of a photon. For example, using the equation** E=hf where E is energy, h is the Planck constant and f is the frequency of the photon**. Also, using the equation** c =λν where c is the speed of light, λ is the wavelength and ν is the frequency of the photon.**

It's also used in the famous equation of **Einstein E=mc^2 where E represents the energy, m the mass and c the speed of light.**

## 10 Interesting Facts of Speed of Light

- Is the fastest speed at which anything can travel in the universe.
- It is a fundamental physical constant and is denoted by the symbol "c".
- Is approximately 299,792,458 meters per second m/s or 299,792.458 kilometers per second km/s.
- Is considered to be an "invariant" speed, meaning that it is the same for all observers regardless of their relative motion.
- The speed of light is a fundamental concept in physics and is used in the development of many scientific theories, including those in the fields of optics, electromagnetism, and relativity.
- Is used in many equations and formulas in physics, including those related to energy, frequency, and distance.
- The famous equation of Einstein E=mc^2 where E represents the energy, m the mass and c the speed of light.
- The speed of light is constant in vacuum and any other medium, but the speed of light in mediums can vary, depending on the properties of the medium.
- Is the upper limit for the speed of information and the speed of causality in the universe.
- Is not affected by the motion of the source or observer; this is known as the principle of relativity.

**Video Tutorial: Speed of Light Explained**

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