Time Travel For Real This Time with Brian Greene & Neil deGrasse Tyson

The script begins with a discussion on the concept of time travel, suggesting that all events are immutable and unchangeable. It references the idea that if one were to travel back in time, they would only fulfill the set of events that led to their existence in the first place. The conversation is set against the backdrop of Charles Dickens' 'A Christmas Carol', a classic novel that explores themes of time through the Ghosts of Christmas Past, Present, and Future. The guest, theoretical physicist Brian Greene, is introduced as an expert on the subject, with his work on time, space, and the universe being highlighted.

This paragraph delves into the scientific aspects of time travel, particularly focusing on Einstein's theories of relativity. It explains how Einstein's Special Relativity showed that time elapses at different rates depending on one's speed, and his General Relativity revealed that gravity also affects the passage of time. The discussion includes examples such as geosynchronous satellites and the famous 'twin paradox' to illustrate these concepts. The conversation also touches on the practical implications of these theories, such as the need to adjust clocks on satellites to account for these relativistic effects.

The script continues with an exploration of what modern physics, specifically Einstein's theories, can contribute to our understanding of time travel. It discusses the possibility of time travel to the future and the constraints on traveling to the past. The concept of a 'self-consistent' timeline is introduced, suggesting that any attempt to change the past would only reaffirm the events that led to the present. The conversation also touches on the philosophical implications of time travel, including the idea that it might negate free will.

This section of the script discusses the role of time travel in literature and film, using the example of a character who attempts to prevent a tragic event but finds that the event is inherent in the timeline. It suggests that one's actions in the past are part of the causal chain of events that have already occurred. The script also introduces the idea of a multiverse, where time travel could involve moving between parallel universes, thus avoiding the paradoxes associated with changing one's own timeline.

The conversation turns to the nature of time and the behavior of photons, which travel at the speed of light. It explores the idea that, from the perspective of a photon, time would appear to stop, although the panelists caution against ascribing human-like experiences to photons. The discussion also addresses the philosophical implications of time travel, including the potential loss of free will and the eternal, unchanging nature of past events.

The script engages with the topic of time travel in Hollywood films, asking which film best depicts the concept and discussing the potential need for regulation if time travel were possible. The panelists consider the implications of time travel for changing past events and the potential paradoxes that could arise. They also touch on the idea that time travelers might be constrained in their actions, preventing them from altering the past in significant ways.

This paragraph explores the effects of time dilation on cellular aging, suggesting that all physical processes, including cellular aging, occur at a rate dictated by the flow of time. The conversation explains that time dilation, as predicted by Einstein's theories, would affect all processes equally, meaning that even one's thoughts would slow down in a strong gravitational field. The panelists emphasize that these effects are not due to the direct influence of gravity on one's physiology but are instead a result of the fabric of space-time itself.

The script delves into the concept of wormholes as a potential mechanism for time travel. It describes wormholes as tunnels that can connect different points in space-time, with the possibility of using them to travel both forward and backward in time. The conversation also addresses the practical considerations of using wormholes for time travel, such as the need to ensure that one exits the wormhole at a specific location in space as well as time.

The discussion continues with an exploration of time travel paradoxes and how they might be circumvented through the multiverse theory. The panelists consider the idea that time travelers might not be able to change their own past but could instead create changes in parallel universes. This approach avoids the paradoxes associated with altering one's own timeline and suggests that each universe represents a different set of outcomes.

This section of the script addresses the hypothetical detection of tachyons, particles that could potentially travel faster than light, and the implications of time travel for understanding the universe's origins. The conversation touches on the possibility of time travel to a point before the Big Bang, suggesting that there may be no 'before' in the context of the universe's beginning. The panelists also discuss the potential for multiple universes and the idea that our Big Bang may not have been the first in a series of cosmic events.

The script concludes with a reflection on Charles Dickens' use of time travel in 'A Christmas Carol', drawing parallels with the concept of wormholes and parallel universes. It suggests that Dickens' story may have invoked a form of time travel where characters observe outcomes in alternate realities rather than directly interacting with their own past. The discussion highlights how such a narrative approach allows for the exploration of different outcomes without altering the established timeline.