# Relativity of Simultaneity | Special Relativity Ch. 4 | Summary and Q&A

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April 26, 2018
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minutephysics
Relativity of Simultaneity | Special Relativity Ch. 4

## TL;DR

The relativity of simultaneity states that events that are simultaneous for one observer may not be simultaneous for another observer in motion.

## Key Insights

• 🖼️ Lorentz transformations represent the change of perspective between non-moving and moving frames of reference.
• ⌛ Simultaneous events for one observer will appear at different times for another observer in motion.
• 👾 The relativity of simultaneity applies to both time and space, as events at the same place in space can appear at different times from a moving perspective.
• 🐎 The distance between events and the speed of the observer affect the amount of desynchronization in simultaneity.
• ❓ The effects of the relativity of simultaneity are usually negligible in everyday situations.
• 🦾 The spacetime globe provides a mechanical implementation of Lorentz transformations.
• 🧩 Brilliant.org offers a course on special relativity that explores the details of relativity of simultaneity and provides puzzles and problems to enhance understanding.

## Transcript

In our universe, when you change from a non-moving perspective to a moving one, or vice versa, that change of perspective is represented by a what's called Lorentz transformation, which is a kind of squeeze-stretch rotation of spacetime that I've mechanically implemented with this spacetime globe. A quick reminder - spacetime diagrams plot position... Read More

### Q: What is the relativity of simultaneity?

The relativity of simultaneity refers to the fact that events that are simultaneous for one observer may not be simultaneous for another observer in motion. This is a consequence of Lorentz transformations and the lack of an absolute notion of time.

### Q: How do Lorentz transformations represent changes in perspective?

Lorentz transformations visually represent changes in perspective, specifically the squeeze-stretch rotation of spacetime. They demonstrate how events that were simultaneous or at the same place for one observer get out of alignment with each other when viewed from a moving perspective.

### Q: How does distance affect the relativity of simultaneity?

The farther away events are from an observer, the more their time from a new perspective (simultaneity) will be out of sync with events closer to the observer. This is due to the x component in the Lorentz Transformation equations.

### Q: Can we notice the effects of the relativity of simultaneity in everyday situations?

In everyday situations, such as normal speeds and distances, the effects of the relativity of simultaneity are minuscule and not noticeable. It would require extreme speeds and distances, such as comparing objects farther apart than the Earth and Moon while moving at half the speed of light, to notice a significant difference in simultaneity.

## Summary & Key Takeaways

• Lorentz transformations represent the change in perspective when transitioning between non-moving and moving frames of reference.

• Simultaneous events from one observer's perspective may not be simultaneous for another observer due to the relativity of simultaneity.

• The farther away events are from an observer, the more out of sync they will appear from the perspective of a moving observer.