According to our current understanding of physics, objects with mass cannot be accelerated to or beyond the speed of light. As an object with mass approaches the speed of light, its relativistic mass increases, and it requires an infinite amount of energy to reach the speed of light itself. This is described by Einstein's theory of special relativity.
However, let's consider the hypothetical scenario of an object with zero mass (such as a photon, which is a particle of light) being accelerated to the speed of light. In this case, we don't encounter the issue of infinite energy requirements, as zero-mass particles naturally travel at the speed of light.
If such an object were to be accelerated to the speed of light, several interesting phenomena would occur:
Time Dilation: According to the theory of special relativity, time dilation occurs as an object approaches the speed of light. For the object moving at the speed of light, time would effectively stand still from its perspective, while time would continue to pass for observers in other reference frames.
Length Contraction: Length contraction is another consequence of special relativity. As an object approaches the speed of light, its length in the direction of motion appears to contract from the perspective of a stationary observer. For an object with zero mass traveling at the speed of light, its length would contract to zero.
Massless Particles: Since we are considering an object with zero mass, the concept of relativistic mass doesn't apply. Massless particles, like photons, always travel at the speed of light and have zero rest mass. They can only exist and propagate at this speed.
It's important to note that these phenomena are based on our current understanding of physics and are consistent with the theory of special relativity. However, exploring the behavior of objects traveling at or beyond the speed of light is still an area of ongoing scientific research and theoretical speculation.