According to our current understanding of physics, which is based on the theory of relativity, traveling faster than the speed of light or going back in time more than one second would lead to several consequences and paradoxes. Here are a few of them:
Time Dilation: As an object approaches the speed of light, time dilation occurs. This means that time slows down for the moving object relative to a stationary observer. If an object were to exceed the speed of light, time dilation would become imaginary, implying a violation of causality and a breakdown of our current understanding of physics.
Causality Paradoxes: If an object could travel faster than light, it would be possible to observe effects happening before their causes, leading to causality paradoxes. For example, the "tachyonic antitelephone" paradox proposes a situation where a signal is sent from the future to the past, allowing a person to send information to themselves before the information is known. This violates our understanding of cause and effect.
Energy Requirements: As an object with mass approaches the speed of light, its relativistic mass increases. To accelerate it further would require an infinite amount of energy, which is not feasible with our current understanding of physics.
Relativity of Simultaneity: The concept of "simultaneity" depends on the observer's frame of reference. If an object could travel faster than light, the order of events would be subject to the observer's frame of reference, leading to a breakdown of a universally agreed-upon notion of simultaneous events.
It's important to note that these consequences and paradoxes arise based on our current understanding of physics. However, if new scientific theories or discoveries emerge in the future, our understanding of these concepts may change.