According to the theory of relativity, as an object approaches the speed of light, time dilation occurs. Time dilation means that time appears to pass more slowly for the object in motion relative to an observer at rest.
If someone were to travel at the speed of light, two things would happen:
From the perspective of an observer at rest, time would appear to stand still for the person traveling at the speed of light. This means that for the person traveling, no time would have passed. However, this scenario is not physically possible because an object with mass cannot reach or exceed the speed of light.
From the perspective of the person traveling, the journey would seem to take an instant. This is due to the time dilation effect, where time appears to slow down for the person traveling at high speeds. However, since the person is traveling at the speed of light, time dilation would be infinite, and the journey would seem to be instantaneous.
It's important to note that these conclusions are based on the theory of relativity, and they describe the behavior of objects approaching the speed of light. As mentioned before, it is not physically possible for an object with mass to reach or exceed the speed of light.