1. What is the Speed of Light?

The speed of light in vacuum, commonly denoted as c, is a universal physical constant important in many areas of physics. Its exact value is 299,792,458 metres per second (approximately 300,000 km/s or 186,000 mi/s).

2. Importance of the Constant

The speed of light is fundamental to physics and appears in many equations:

Where:

• \( E \) — Energy
• \( m \) — Mass
• \( c \) — Speed of light

Explanation: This famous equation shows the relationship between mass and energy.

3. Historical Context

Details: The speed of light was first measured by Ole Rømer in 1676 using observations of Jupiter's moons. In 1983, the meter was redefined in terms of the speed of light.

4. Applications

Uses: The constant is crucial in relativity, quantum mechanics, GPS technology, astronomy, and telecommunications.

5. Frequently Asked Questions (FAQ)

Q1: Why is the speed of light considered constant?
A: According to Einstein's theory of relativity, the speed of light in vacuum is the same for all observers, regardless of their motion relative to the light source.

Q2: Can anything travel faster than light?
A: According to our current understanding of physics, no object or information can travel faster than light in vacuum.

Q3: How was the speed of light measured?
A: Historically through astronomical observations, later with precise laboratory experiments using mirrors and rotating wheels.

Q4: Does light always travel at this speed?
A: No, light travels slower when passing through transparent materials like water or glass.

Q5: Why is 'c' used to denote the speed of light?
A: It comes from the Latin word "celeritas" meaning swiftness or speed.