- #1
DocZaius
- 365
- 11
I am beginning a textbook on SR and I have come across the introductory example of disagreement regarding simultaneity.
John is in a lab and Mary flies through the lab's corridor on a rocket. The rocket has an antenna. The antenna strikes John's pen in his shirt pocket and creates a spark. 2 meters down the corridor, the rocket's antenna strikes the fire extinguisher and creates a spark.
Now the book immediately says that John's span of time between each spark is different than Mary's span of time between each spark.
The book says that John calculated a certain time between each spark. Does that time represent John's measurement between each spark's light arriving at his eyeballs? Or does it instead represent John's measurement between each spark's light arriving at his eyeballs with him correcting for signal latency and considering how long it took for each spark's light to reach his eyeball?
In other words, did John set t=0 for the time the first spark's light reached his eyeball and t=36 nanoseconds for the time the second spark's light reached his eyeball and leave it at that? Or did he instead set t=0 for the time the first spark's light reached his eyeball minus the amount of time it took for light to travel 0.1 meters from the shirt pocket to his eyeball, with the same correction for the fire extinguisher?
Basically, my question is: Is it standard in SR problems for such declarations of time lapses between events from an observer's point of view to implicitly correct for light distance travel, or merely (and crudely) base them on when light of such events reached the observer?
I am very surprised and disappointed that the textbook did not make it clear which method John used to calculate the time lapse between each event.
John is in a lab and Mary flies through the lab's corridor on a rocket. The rocket has an antenna. The antenna strikes John's pen in his shirt pocket and creates a spark. 2 meters down the corridor, the rocket's antenna strikes the fire extinguisher and creates a spark.
Now the book immediately says that John's span of time between each spark is different than Mary's span of time between each spark.
The book says that John calculated a certain time between each spark. Does that time represent John's measurement between each spark's light arriving at his eyeballs? Or does it instead represent John's measurement between each spark's light arriving at his eyeballs with him correcting for signal latency and considering how long it took for each spark's light to reach his eyeball?
In other words, did John set t=0 for the time the first spark's light reached his eyeball and t=36 nanoseconds for the time the second spark's light reached his eyeball and leave it at that? Or did he instead set t=0 for the time the first spark's light reached his eyeball minus the amount of time it took for light to travel 0.1 meters from the shirt pocket to his eyeball, with the same correction for the fire extinguisher?
Basically, my question is: Is it standard in SR problems for such declarations of time lapses between events from an observer's point of view to implicitly correct for light distance travel, or merely (and crudely) base them on when light of such events reached the observer?
I am very surprised and disappointed that the textbook did not make it clear which method John used to calculate the time lapse between each event.
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