According to our current understanding of physics, time moves only in one direction, commonly referred to as the "arrow of time," and that direction is forward. This concept is deeply ingrained in our everyday experience and is supported by various physical phenomena and observations. However, I should note that the nature of time is a complex and ongoing subject of scientific investigation, and there are still many unanswered questions and areas of active research.
Regarding the possibility of backward time at the subatomic level, there is no experimental evidence or widely accepted theoretical framework that suggests time can flow backward on such a small scale. In fact, the fundamental laws of physics, as we currently understand them, do not inherently distinguish between the past and the future. This means that the equations describing the behavior of subatomic particles are time-symmetric, meaning they are equally valid if time were reversed. However, this time symmetry does not imply that time can actually flow backward; it simply reflects the symmetry of the underlying equations.
It's important to note that while there are processes at the subatomic level that appear to be time-reversible within the framework of classical physics, such as the motion of individual particles, the arrow of time emerges when considering macroscopic systems and the statistical behavior of large numbers of particles. This is due to the concept of entropy, which generally increases with time in closed systems, leading to the irreversibility of certain processes.
In summary, our current understanding of physics suggests that time moves only forward, and there is no well-established evidence or theoretical framework supporting the existence of backward time at the subatomic level. However, the nature of time is a subject of ongoing scientific inquiry, and future discoveries or advancements in our understanding may lead to new insights and perspectives on this topic.