According to the theory of special relativity, as formulated by Albert Einstein, several interesting effects would occur if an object were to travel at or near the speed of light. However, it's important to note that this scenario is purely hypothetical as no massive object with mass can actually achieve the speed of light.
Firstly, as an object with mass approaches the speed of light, its relativistic mass increases, meaning it would require an infinite amount of energy to accelerate it to the speed of light itself. This is a consequence of the relativistic equation for mass-energy equivalence, E=mc², where E is the energy, m is the mass, and c is the speed of light.
As an object's velocity approaches the speed of light, time dilation occurs. From the perspective of an observer at rest, time appears to slow down for the moving object. This means that the moving object's internal processes, such as its biological functions or the operation of clocks, would appear to slow down from an external perspective. However, for the person traveling at high speeds, their experience of time would remain constant.
Length contraction is another effect of traveling at relativistic speeds. As an object moves faster, its length in the direction of motion appears to contract from the perspective of an observer at rest. Again, this effect is not noticeable to the person in the moving frame of reference.
Furthermore, the relativistic effects would intensify as the object approaches the speed of light. At the speed of light itself, time dilation and length contraction would become infinite, and the object would have infinite mass, which is not physically possible.
It's important to emphasize that these effects are theoretical consequences derived from the mathematical formulation of special relativity. They describe how time, space, and mass behave at high speeds but are not achievable or observable in practice for objects with mass.