The reason why objects with mass cannot go faster than the speed of light is deeply rooted in the principles of special relativity, a fundamental theory of physics developed by Albert Einstein. According to special relativity, the speed of light in a vacuum, denoted by "c," is an absolute speed limit in the universe. No object with mass can ever reach or exceed this speed. There are several key reasons for this limitation:
Mass-Energy Equivalence: In special relativity, the famous equation E=mc^2 relates an object's energy (E) to its mass (m). This equation shows that mass and energy are interchangeable, and even an object at rest (with zero kinetic energy) has an inherent energy equal to mc^2. As an object accelerates, its kinetic energy increases, and the faster it moves, the more energy it gains.
Increasing Energy Requirement: As an object with mass approaches the speed of light, its kinetic energy keeps increasing without bound. According to the equation for kinetic energy (KE = (γ - 1)mc^2, where γ is the Lorentz factor), the energy required to accelerate the object further increases as its speed approaches the speed of light. Consequently, it would take an infinite amount of energy to accelerate an object with mass to the speed of light, making it practically impossible.
Time Dilation: As an object approaches the speed of light, time dilation occurs. This means that time appears to slow down for the object as observed from a stationary reference frame. As the object's speed gets closer to the speed of light, time dilation becomes more pronounced. At the speed of light itself, time would effectively stop for the object, making it impossible for it to achieve any further acceleration.
Lorentz Contraction: Another effect of relativistic speeds is the Lorentz contraction, which causes objects to appear shorter along the direction of their motion as observed from a stationary frame. This contraction also becomes more significant as an object approaches the speed of light, making it increasingly difficult to further accelerate the object.
Due to these effects of special relativity, objects with mass cannot reach or exceed the speed of light in a vacuum. As an object approaches the speed of light, its energy requirements become infinite, time appears to stand still for it, and its length contracts, preventing it from crossing this cosmic speed limit. Only massless particles, such as photons (particles of light), travel at the speed of light in a vacuum, as they have no rest mass and are inherently massless.