# Light travel in space of varying timeflow

• wimms
In summary, the conversation discusses the concept of time dilation and how it relates to the curvature of spacetime. The external observer perceives the time dilation as a result of the region of space being "larger" or "curved" compared to flat space, while the observer on the rocket experiences no time dilation but instead perceives an acceleration through the region. This can be attributed to the distortion of spacetime in the region.
wimms
I'm having trouble to visualise this scenario. Please help to sort it out. Just an exercise to perceive relative timeflows.

Suppose perfectly flat empty space. Suppose there are regions of space where timeflow slows down twice. Suppose a rocket at c/2 traveling through such region of space. Now there are 2 perceptions of that space region, one for external observer, and other for traveling observer.

For external observer, rocket approach that space, slows down to c/4 (same distance in twice external time), take some time to pass it, then accelerate back to c/2 again.
For observer on rocket, no slowdown, instead that section of space seems to be passed faster (timeflow change is not perceived) than expected when calculated outside, or perceived acceleration occurs.

Velocity=distance/time. We measure distances in ct.

If velocity of light c is fixed, then in regions of space where timeflow changes, it must be perceived as variation of distance. Or, while entering such space region, visual perception of stars or external objects should change as if they jump off further away, and then back closer when leaving that region. But, because there was perceived acceleration through that space, this cancels out in forward direction, and perceived is uniform travel velocity through that region. Only visual perception changes due to limited c.

For external observer, light traveling through that region seems to take unexpectedly more external time than would be calculated outside based on flat space. Or, basically, for external observer that region of space seems 'larger' than expected from flat space, or is 'curved'.

If the region of space is spherical with uniform spread of time rate around it, would it look like gravitational spacetime curvature?

I'm confused about perceived time and space dilation for observers. Is it at all reasonable path of thinking?

Yes, it is reasonable to think of the region of space as a curved spacetime, where time and space are distorted in a similar way. The external observer perceives the time dilation as an effect of the curvature of spacetime around the region, while the observer on the rocket experiences no time dilation but instead perceives an acceleration through the region. This is because the observer on the rocket is not affected by the warped spacetime, and therefore does not experience the same time dilation as the external observer.

## 1. How does the speed of light change in different timeflows?

The speed of light is a constant, meaning it does not change regardless of the timeflow. This is one of the fundamental principles of physics known as the speed of light postulate.

## 2. Can light travel faster than the speed of light in certain timeflows?

No, the speed of light is the maximum speed at which any object, including light, can travel. It is a universal speed limit and cannot be exceeded, regardless of the timeflow.

## 3. How does the perception of light change in varying timeflows?

In different timeflows, the perception of light may appear to be faster or slower compared to our own timeflow. This is due to the concept of time dilation, which occurs when an object is moving at high speeds relative to another observer. This means that the rate at which time passes for an object will be different depending on the relative speed between the observer and the object.

## 4. How does the distance of light travel in space change in varying timeflows?

The distance that light travels in space is also affected by time dilation. For example, if an object is moving at high speeds, the distance it travels in a certain amount of time will be perceived as shorter by an observer in a different timeflow. This is known as length contraction.

## 5. How does the phenomenon of time travel affect the travel of light in space?

The concept of time travel is currently theoretical and has not been proven to be possible. However, if time travel were to exist, it could potentially affect the travel of light in space. It is believed that time travel could potentially cause disruptions in the fabric of space-time, which could influence the travel of light. However, this is still a subject of ongoing research and remains largely unknown.

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