Neil deGrasse Tyson’s Guide To Time Travel — StarTalk 101

Summary

This discussion delves into the fascinating concepts of controlled backward time travel, focusing on the implications of wormholes and the nature of observing such travel from a third-person perspective. It explores how wormholes could theoretically allow for travel between different points in space and time, potentially leading to intriguing scenarios where one could enter a wormhole and emerge at another location in a different time. The conversation also touches on the ideas of information, entropy, and the paradoxes associated with time travel, such as the grandfather paradox, while referencing popular culture representations of time travel in movies and theories proposed by scientists like Stephen Hawking.

Takeaways

• 😄 Time travel to the past could be possible through wormholes, where one opening is in the future and the other is in the past, allowing you to travel between the two points in time.
• 🤔 The 'grandfather paradox' poses a significant challenge to the idea of backwards time travel, as preventing your ancestors from meeting could erase your own existence and the ability to travel back in time.
• 🔗 Introducing minor changes to the past, like delaying conception by a few minutes, could result in an entirely different person being born, rather than simply altering your own timeline.
• ⏰ Time travel to the future is theoretically possible by traveling close to the speed of light, where time dilation would cause the traveler to age slower than those on Earth, effectively jumping them forward in time.
• 🕰️ GPS satellites orbiting Earth have their clocks adjusted to account for the effects of time dilation predicted by Einstein's theory of relativity.
• ❓ The absence of time travelers visiting us from the future could be seen as evidence that time travel may never be invented, unless time travelers are deliberately hiding their existence.
• 👥 In higher dimensions beyond our familiar 3D space and one time dimension, our conventional notions of time may not apply, allowing access to an individual's entire timeline simultaneously.
• 🔄 The hypothetical 'tachyon' particle, which could move faster than light, could theoretically send information backwards in time, but may paradoxically cause the very event it was trying to prevent.
• 🎥 Time travel movies often explore different interpretations and implications of time travel, but generally avoid providing explicit scientific explanations for the mechanics involved.
• 🧐 The philosophical and scientific implications of time travel, such as the preservation of cause and effect, and the consistency of the laws of physics, remain highly debated and unresolved.

Q & A

What is the concept of wormholes in relation to time travel?

Wormholes are theoretical tunnels through spacetime that can connect distant points in space and potentially allow travel between different times. If the entrances of a wormhole are moved relative to each other or one is placed near a black hole, it could create a time difference between the two ends, enabling travel to the past or future.

How does the Marvel Universe's portrayal of portals differ from theoretical wormholes in relation to time travel?

In the Marvel Universe, characters like Doctor Strange use portals to move through space, not time. Theoretical wormholes, however, offer the fascinating possibility of not just spatial shortcuts but also tunnels through time, which the Marvel Universe has not explored.

What is the grandfather paradox in the context of time travel?

The grandfather paradox is a theoretical problem that arises when considering the possibility of time travel to the past. It involves a time traveler going back in time and preventing their grandparents from meeting, thus preventing the time traveler's own birth and creating a logical inconsistency or paradox.

How do GPS satellites illustrate Einstein's theory of relativity in practice?

GPS satellites orbit Earth at a high altitude where the effects of Einstein's general theory of relativity are observable. Their clocks tick slightly faster than those on Earth's surface due to being farther from Earth's gravitational pull. This difference is accounted for to ensure the accurate timing necessary for GPS functionality.

What is a tachyon and how does it relate to time travel?

A tachyon is a hypothetical particle that moves faster than the speed of light. According to theoretical physics, if it were possible, crossing the speed of light would result in time moving backward for such a particle. Tachyons have been speculated to enable communication or travel back in time.

Why is traveling forward in time considered possible, while traveling backward presents paradoxes?

Traveling forward in time is possible through the effects of high speeds on time dilation, as predicted by Einstein's theory of relativity. Traveling backward in time, however, introduces logical paradoxes such as the grandfather paradox, challenging the consistency of cause and effect.

How does the movie 'Contact' portray wormhole travel?

In the movie 'Contact', the protagonist travels through what is presumed to be a wormhole to meet extraterrestrial beings. This travel is depicted not as a complex journey but more like stepping through a portal, highlighting the concept of wormholes as shortcuts through space and potentially time.

Can time travel affect entropy and information?

The script hints at the relationship between time travel, entropy, and information, suggesting that traveling through time could have implications on the universe's entropy and the flow of information. Entropy is a measure of disorder, and time travel could theoretically alter the entropy of a system, affecting the direction and flow of information.

What are closed timelike curves and why are they significant in theoretical physics?

Closed timelike curves are theoretical paths through spacetime that return to the same point in space and time, essentially allowing for time loops. They are significant because they challenge our understanding of cause and effect and the linear progression of time, raising questions about the consistency of events in a universe where time travel is possible.

Why do some scientists and theories suggest that time travel to the past may never be possible?

Some scientists and theories suggest that time travel to the past may never be possible due to the paradoxes it introduces, such as the grandfather paradox, which challenge the consistency of cause and effect. Additionally, Stephen Hawking proposed a time travel conjecture that might mathematically or experimentally prove such travel impossible to avoid these paradoxes.