PBS Space Time Season 2019 Episode 34 Is Time Travel Impossible?

In this episode of PBS Space Time titled "Is Time Travel Impossible?", the hosts dive into the question that has fascinated people for centuries: can we travel through time? Through a series of thought experiments, the episode explores the possibilities and limitations of time travel, using the latest scientific knowledge to shed light on this age-old question.

The episode begins with an overview of the four-dimensional spacetime, explaining how space and time are interconnected in a single fabric that expands and contracts with the universe. From this starting point, the hosts delve into the concept of time travel, examining the various forms it might take, from travel to the past to travel to the future, and all the paradoxes and complications that can arise.

One of the key points the episode makes is that time travel is not necessarily impossible according to our current understanding of physics, but it may be incredibly difficult, if not impossible, to achieve in practice. This is because time travel requires us to bend the fabric of spacetime in such a way that it creates a closed timelike curve, essentially a loop that allows us to return to our own past or visit our own future.

The problem is, our current understanding of the laws of physics suggests that such curves might be inherently unstable, leading to paradoxes and inconsistencies that could threaten the very fabric of spacetime. As the hosts explain, this is due to the fact that time travel violates many of the basic principles of causality and relativity, making it difficult to reconcile with our current understanding of the universe.

Throughout the episode, the hosts use a variety of thought experiments to illustrate the challenges and limitations of time travel. They consider what might happen if we were to go back in time and accidentally prevent our own birth, or if we were to travel to the future and witness events that could have profound impacts on our present-day lives. They also explore some of the theoretical frameworks that physicists have developed to account for the possibility of time travel, including the concept of parallel universes and the idea of using black holes as portals to other parts of the universe.

Despite the many challenges and difficulties associated with time travel, the episode ends on a cautiously optimistic note. The hosts suggest that with continued scientific research and breakthroughs in our understanding of the universe, it may one day be possible to achieve some form of time travel, whether it's to the past, the future, or other dimensions of reality altogether.

Overall, "Is Time Travel Impossible?" is a fascinating exploration of one of the most intriguing questions in science and philosophy. Through a mix of theory, thought experiments, and cutting-edge scientific research, the episode provides a nuanced and thought-provoking examination of the possibilities and implications of time travel, inspiring viewers to ponder the mysteries of the universe and the limits of human understanding.