Light travels at a constant speed in a vacuum, commonly denoted as "c," which is approximately 299,792,458 meters per second (or about 186,282 miles per second). This speed is a fundamental constant in physics and plays a central role in the theory of special relativity.
According to special relativity, objects with mass cannot reach or exceed the speed of light in a vacuum. As an object with mass approaches the speed of light, its energy and momentum increase dramatically, requiring an infinite amount of energy to accelerate it to exactly the speed of light. Therefore, it is not possible for anything with mass to achieve or surpass the speed of light.
However, it's important to note that special relativity does allow for massless particles, like photons (particles of light), to travel at the speed of light. Photons have no rest mass, and they always move at c in a vacuum. This is why light itself is observed to travel at this constant speed.
While objects with mass cannot reach the speed of light, they can still approach it, but their energy and momentum increase significantly as they do so. As an object with mass accelerates towards c, its mass appears to increase, and time dilation effects occur, meaning time appears to slow down for the object as observed from a stationary reference frame.
In summary, light travels at a constant speed denoted as c, which is approximately 299,792,458 meters per second. While massless particles like photons can travel at this speed, objects with mass cannot reach or exceed it due to the principles of special relativity.