According to Albert Einstein's theory of relativity, specifically the theory of special relativity, the concept of time dilation arises when an object moves at speeds close to the speed of light. Time dilation suggests that time appears to pass more slowly for objects that are moving relative to an observer at rest.
As an object approaches the speed of light, time dilation becomes more pronounced. From the perspective of an observer on that object, time would appear to be passing normally. However, for an observer in a different reference frame, such as a stationary observer, time on the moving object would appear to be passing more slowly. This effect is often described by saying that time "slows down" for the moving object.
Now, if we consider an object moving at the speed of light, it's important to note that according to the theory of special relativity, no massive object can reach or exceed the speed of light. As an object with mass approaches the speed of light, its relativistic mass increases, requiring an infinite amount of energy to accelerate it to the speed of light. Therefore, it is not possible for an object with mass to actually reach the speed of light.
That being said, if we imagine a hypothetical scenario where an object with mass could reach the speed of light, time dilation would indeed occur. However, it's important to note that the concept of time stopping for an object moving at the speed of light is a simplification used to illustrate the effects of time dilation. It does not mean that all processes within the object would come to a complete halt.
From the perspective of an observer in a different reference frame, the processes within the object would appear to slow down, but they would not necessarily stop completely. However, the details of how physical processes would behave near or at the speed of light are beyond the scope of classical physics and would require a more comprehensive understanding of relativistic quantum mechanics.