What is the speed of light in a vacuum?

The speed of light in a vacuum is approximately 299,792 kilometers per second. This value is often rounded to 300,000 km/s for simplicity in many contexts, but the more precise measurement is critical for scientific accuracy and is used as a fundamental constant in physics, denoted by the symbol "c". The speed of light is essential in various areas of physics, including the theories of relativity, where it plays a key role in understanding the relationship between space and time.

Other values listed, such as 150,000 km/s and 450,000 km/s, do not correspond to accepted measurements for the speed of light and lack acceptance in the scientific community. Therefore, the correct answer reinforces a crucial aspect of physical science and our understanding of the universe.