In Einstein's equation E = mc^2, what does the symbol c represent?

In Einstein's equation E = mc^2, what does the symbol c represent?

• A. Planck's constant
• B. Speed of light
• C. Gravitational constant
• D. Boltzmann constant

Answer: (B)

In Einstein's equation, c represents the speed of light in vacuum, a universal constant that is the same for all observers. Its value is about 3.00 × 10^8 meters per second, and it acts as the conversion factor between mass and energy: E = mc^2. Because c^2 is such a huge number, even a small amount of mass corresponds to a very large amount of energy (for example, 1 kg would be about 9 × 10^16 joules). This reflects the idea that mass and energy are two forms of the same thing in relativity. The other constants—Planck's constant, gravitational constant, and Boltzmann constant—appear in different physical contexts (quantum energy, gravity, and thermal energy, respectively) and do not serve this mass–energy relationship.

In Einstein's equation, c represents the speed of light in vacuum, a universal constant that is the same for all observers. Its value is about 3.00 × 10^8 meters per second, and it acts as the conversion factor between mass and energy: E = mc^2. Because c^2 is such a huge number, even a small amount of mass corresponds to a very large amount of energy (for example, 1 kg would be about 9 × 10^16 joules). This reflects the idea that mass and energy are two forms of the same thing in relativity. The other constants—Planck's constant, gravitational constant, and Boltzmann constant—appear in different physical contexts (quantum energy, gravity, and thermal energy, respectively) and do not serve this mass–energy relationship.