Relative Time Question: Train Experiment and Conflicting Views

In summary, three men are on a train moving at high speeds, with one standing at the back, one at the front, and one halfway between them with gunpowder. They set their watches to 1 o'clock when the light from the gunpowder reaches them, but an observer on the ground sees the light reach the back man 2 seconds earlier due to the train's movement. When the train slows down, all three men will see the same time on their watches.
  • #1
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Imagine the following scenario.

There is a long train moving at very fast speeds (approaching light speeds), one man stands at the back of the train with a watch and another at the front. A third man stands exactly halfway between them with some gunpowder and a match. The men at the back agree to set their watches to 1 o clock when the light from the gunpowder reaches them (I said fast and long train so that it will actually take a reasonable time to reach them). A forth man watches from outside the ground.

The gunpowder goes off, and both men set their watches. The third man views this and says it was a fair timing and both had set their watches to the same time. However the man from the ground sees the light reach the man at the back of the train 2 seconds earlier (since relative to him the man at the back is moving towards the light and man at the front away). So he thinks the clocks are set to 1:00 and 1:02.

The train slows down and the man from the ground goes and sees the watches. What will they say?

I'm having a bit of trouble coming up with an answer for this because I know both views are both equally valid views, but the clocks can only say one thing when they all look at it togeather.
 
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  • #2
Hi Alex! :smile:

It's easier if you consider what happens if the back man (after they've set their watches) walks slowly towards the front man.

The observer on the ground will gradually see the times on the watches get closer.

Similarly, if the train gradually slows down, but the two men stay apart, the observer on the ground will gradually see the times on the watches get closer. :smile:
 
  • #3
Ah ok I see thanks.
 

1. What is relative time?

Relative time is a way of measuring time in relation to another event or point in time. It is based on the concept that time is not absolute and can vary depending on the observer's perspective.

2. How is relative time different from absolute time?

Absolute time is a fixed measurement of time that does not change. It is based on a standard unit of time, such as seconds or minutes. Relative time, on the other hand, is a measurement of time that is dependent on a specific reference point and can vary depending on the observer's frame of reference.

3. What are some examples of relative time?

Examples of relative time include the time between two specific events, the time it takes for an object to travel a certain distance, or the time it takes for a process to be completed. It can also refer to time zones, since the time can be different in different parts of the world.

4. How is relative time used in science?

Relative time is a crucial concept in many fields of science, including physics, astronomy, and geology. It is used to understand the relationships between events and to make predictions about future events. For example, in geology, relative time is used to determine the sequence of events that led to the formation of rock layers.

5. Can relative time be measured accurately?

Relative time is a concept rather than a physical quantity, so it cannot be measured in the same way as absolute time. However, it can still be used to make calculations and predictions with a high degree of accuracy, especially when combined with other scientific principles and techniques.

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