Time Travel Lecture Notes

Introduction to Time Travel

• Time travel is often conceptualized as going forward through time every second.
• Time is not a thing that passes but a dimension in which we can move.
• The universe is thought to be four-dimensional: three spatial dimensions and one time dimension, combined into space-time.

Space-Time Movement

• Moving through the time dimension is how we experience time passing.
• In the time dimension, we can only move forward; there are no detours.
• All objects in the universe move at the speed of light through space-time.
  • Speed through space-time = speed through time + speed through space.
• It's impossible to remain still; even at rest, we move through time.

Light and Time

• Photons (light particles) move at the speed of light but don’t experience time.
• From the photon's perspective, there’s no passage of time between emission and absorption.

Twin Paradox and Time Dilation

• Twin Paradox Concept:
  • One twin travels in a fast rocket, the other stays on Earth.
  • They age at different rates due to differences in speed through space and time.
• Moving faster through space results in moving slower through time (time dilation).
• This principle allows for time travel into the future.

Gravitational Time Dilation

• Massive objects, like black holes, bend space-time, causing nearby time to pass slower.
• On Earth, gravity affects time very slightly.
• Near a black hole, time slows significantly for someone approaching the event horizon.

Theoretical Backward Time Travel

• Moving faster than light (superluminal) could allow backward time travel.
• Theoretical particles called tachyons could theoretically move backward in time.
• Tachyons would have properties like increasing speed as they lose energy.
• Current science hasn’t found evidence of tachyons; their existence is speculative.

Limitations of Time Travel

• The theory of relativity forbids objects starting slower than light from reaching light speed.
• Time travel to the past remains theoretically impossible with our current understanding.
• The past is inaccessible, unlike the present and future.

Focus on the Present and Future

• It’s essential to focus on the present and the future, which is more feasible to shape.
• Being present offers opportunities for growth and learning.

Learning and Resources

• Brilliant offers courses and interactive lessons to build problem-solving skills and scientific knowledge.
• Courses include scientific thinking and specialized topics in science and technology.
• A partnership with Kurzgesagt provides learners more in-depth insights into popular science topics.

Conclusion

• While time travel to the past is not achievable, understanding time enables us to appreciate the present and plan for the future.
• Engage with time travel concepts through educational resources and interactive learning.