The speed of light in a vacuum is approximately 299,792,458 meters per second, which is commonly approximated as 3 × 10^8 meters per second. This approximation is often used for simplicity in calculations and communication.
The exact value of the speed of light in a vacuum is defined to be exactly 299,792,458 meters per second according to the International System of Units (SI). This value is derived from the definition of the meter and the second. The meter is defined as the distance light travels in a vacuum in 1/299,792,458 of a second. Therefore, the speed of light is exactly 299,792,458 meters per second by definition.
However, for practical purposes and ease of use, the value of the speed of light is often approximated as 3 × 10^8 meters per second. This approximation allows for simpler calculations and is close enough for most everyday applications where high precision is not required.