The maximum possible velocity of electromagnetic (EM) radiation in a vacuum is the speed of light, often denoted as "c." In a vacuum, such as outer space, the speed of light is approximately 299,792,458 meters per second (or about 186,282 miles per second).
According to the theory of special relativity, proposed by Albert Einstein, the speed of light in a vacuum is considered an absolute constant. It is a fundamental property of the universe and acts as an upper limit for the velocity of any physical object or information.
There are a few reasons why we cannot exceed the speed of light:
Time dilation: As an object approaches the speed of light, time dilation occurs, meaning time appears to pass slower for the object relative to a stationary observer. As an object with mass accelerates towards the speed of light, its relativistic mass increases, requiring more and more energy to accelerate further. As a result, it would take an infinite amount of energy to reach or exceed the speed of light.
Lorentz transformation: Special relativity also introduces the Lorentz transformation equations, which describe how measurements of space and time change when transitioning between different inertial reference frames. These equations imply that as an object's velocity approaches the speed of light, its length contracts in the direction of motion, and time dilates. These effects prevent the object from reaching or surpassing the speed of light.
Causality violation: If information were to travel faster than the speed of light, it could potentially lead to violations of causality, where an effect could precede its cause in certain reference frames. This would contradict our current understanding of cause and effect relationships and lead to logical inconsistencies.
Based on these principles, it is currently believed that the speed of light is an absolute cosmic speed limit, and no physical object with mass can reach or exceed this velocity.