According to our current understanding of physics, an object with mass cannot travel at the speed of light. As an object with mass approaches the speed of light, its relativistic mass would increase, requiring an infinite amount of energy to accelerate it to the speed of light. Additionally, time dilation effects would occur, causing time to slow down for the object relative to an observer at rest.
If we consider a thought experiment in which an object could somehow achieve the speed of light, the consequences become even more intriguing. From the perspective of the object traveling at the speed of light, time would effectively stand still. This phenomenon is known as "time dilation." However, this does not imply that the object could move backward through space-time or travel backward in time.
The theory of special relativity, proposed by Albert Einstein, states that the speed of light is an absolute speed limit in the universe. Objects with mass cannot reach or exceed this speed because it would require an infinite amount of energy. Furthermore, the theory of causality suggests that cause and effect relationships in the universe occur in a particular order, and backward time travel could potentially lead to paradoxes and logical inconsistencies.
It's important to note that while there are some intriguing theoretical concepts and discussions surrounding time travel, such as closed timelike curves or wormholes, they are still purely speculative and not currently supported by empirical evidence. Time travel, especially backward time travel, remains within the realm of science fiction and has not been demonstrated in practice.