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Old Dec 16th 2017, 11:58 AM   #1
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EMR round trip and one way trip times

Has the issue been proven that one way trip time of EMR between two bodies in inertisl reference frames will be precisely half of the round trip time according to an observer in either body's IRF?
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Old Dec 16th 2017, 02:33 PM   #2
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Originally Posted by wanderer View Post
Has the issue been proven that one way trip time of EMR between two bodies in inertisl reference frames will be precisely half of the round trip time according to an observer in either body's IRF?
Yes. There was a question of it before the one way speed of light was measured but that's no longer the issue since it has been established the its the same regardless of the direction light travels.

For details please see Ohanian's book on SR. If you can't find it I can scan and e-mail you the pages in a PDF file it you'd like. Please look first because that would require a lot of work.
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Old Dec 16th 2017, 05:45 PM   #3
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Thanks, I'll look it up'
Regards; wanderer
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Old Dec 16th 2017, 06:15 PM   #4
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My local library has a copy of Hans C. Ohanian's book 'Special Relativity, a Modern Introduction' available. I will pick it up. Thanks for the lead.
Regards; wanderer.
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Old Dec 17th 2017, 08:15 AM   #5
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Originally Posted by wanderer View Post
My local library has a copy of Hans C. Ohanian's book 'Special Relativity, a Modern Introduction' available. I will pick it up. Thanks for the lead.
Regards; wanderer.
Wonderful!


FYI: When you're searching the internet for answers to your questions I suggest that you consider Wikipedia as unreliable, because it's often incorrect. However it's a useful research tool because it lists references that you can consult to verify or refute the statements of the writer of the Wiki article. Caveat emptor!

I consulted a friend of mine who's an authority on this subject. He \pointed out wo obvious counterexamples to the notion that the one-way speed light is not measurable, namely the first-ever measurements of the speed of light by Roemer (via occultations of the moons of Jupiter) and by Bradley (via aberration of starlight). Both Roemer and Bradley found fairly accurate values for the speed of light, without any use of synchronization of separated clocks.

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Old Dec 17th 2017, 09:17 AM   #6
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I agree with your thoughts about Wikipedia. I haven't got Ohanian's book from the library yet. However, I'll offer a thought about a simple experiment which could answer the question about one way EMR times.
I worked for Hewlett Packard back in the 1960s and one of their event counter instruments was programmable. It could be programmed to measure the additional time caused in a communication link by the addition of a small one inch coupler to the link. It couldn't do that in just a single event transmission over the link. The counter had to average the elapsed time for the transmission of many pulses over the link. How many pulses were required depended on the length of the item added to the link and the accuracy needed.
Now that I am curious about one way transmissions, I have to wonder if that HP event counter, or a current model could be used to resolve the one way EMR issue.
regards; wanderer
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Old Dec 17th 2017, 12:28 PM   #7
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Originally Posted by wanderer View Post
I agree with your thoughts about Wikipedia. I haven't got Ohanian's book from the library yet.
Here's some more information. This one appears to list some of the experiments to measure the one way speed of light

One-way speed of light

The one listed last is an MIT tech review website

https://www.technologyreview.com/s/4...ght-conundrum/

It says
Today, they give us an interesting review of the various ways in which the measurements have been made.
Notice that it says have been made? If you go to other forums you're bound to run into people who think that its never been measured/confirmed.
Don't listen to them, they're all wrong. In fact very long base phased array radar can't work of the one-way speed of light depends on direction and it works quite well. This is one of the things that you'll read about in Ohanian's text.

Try also going to the home page of the American Journal of Physics and search on the phrase "one way speed of light." Their home page is at

http://aapt.scitation.org/journal/ajp/

If there's a paper you'd like to look at then let me know the reference info and I'll get it for you.

Originally Posted by wanderer View Post
I worked for Hewlett Packard back in the 1960s and one of their event counter instruments was programmable. It could be programmed to measure the additional time caused in a communication link by the addition of a small one inch coupler to the link. It couldn't do that in just a single event transmission over the link. The counter had to average the elapsed time for the transmission of many pulses over the link. How many pulses were required depended on the length of the item added to the link and the accuracy needed.
I'm sorry but I don't understand what you just wrote. For example; what is an event counter and what does its programing have to do with this subject? What additional time are you referring to? What are the links that you mentioned? Remember that I'm a physicist, not an electrical engineer. I used to be an electronics technician for several years so I know circuitry. Part of my physics education includes undergraduate and graduate courses in electrodynamics. So I know all the physics of the subject but not the engineering particulars.
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Old Dec 17th 2017, 03:27 PM   #8
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My apologies for being vague. Event counters were digital electronic frequency measurement devices. They could measure the number of cycles of a frequency source pf many mega Hz over a predetermined time or alternately by using an internal clock (frequency source), they could measure the elapsed time between input electrical pulses or cycles of an input frequency. However the particular programmable HP instrument mentioned was able to do something more than that. It had internal memory and could build up the results of millions of repeated measurements and then present a digital display of the average result of all of the measurements.
All such frequency counters suffered from a problem that made any single measurement subject to an error of plus or minus one of the events being counted. Therefore, several events needed to be counted and averaged to get an accurate measurement. Ordinary counters could make one measurement over a predetermined amount of time and that was all it could do.
The HP counter mentioned had the capability to create output pulses which could be connected to a cable (the link) which had the other end connected to an input on the counter. Then the meter was programmed to create output pulses at a chosen rate and make a chosen number (millions) of elapsed time measurements between output and input pulses. After the programmed number of measurements had been made, a digital display showed the average time for all of the measurements.
It seems to me that this was indeed a one=way measurement of EMR between the output and input ports of the instrument.
Regards; wanderer.
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Old Dec 19th 2017, 07:55 PM   #9
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I looked at Ohanian's text and saw that there's only two pages to this subject so I scanned them in and put them into a PDF file. Here it is:
Attached Files
File Type: pdf Ohanian_32-33.pdf (481.1 KB, 6 views)

Last edited by Pmb; Dec 20th 2017 at 01:39 PM.
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Old Dec 20th 2017, 03:00 PM   #10
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one way time for EMR transmissions

Hey Pmb! Thanks, I'm not surprised about the results of one way EMR transmission times measured by the experiments described in the pages of Ohanian's book that you selected.
Before I make any further comments about those experiments, I need to know if etherist theories can be discussed (or even mentioned) in this forum. I don't want to get kicked out of this forum for making 'Crackpot' posts and my comments will be ahhhh---sorta etherist. If that subject is forbidden here, I won't say another word about this string.

Regards; wanderer

Last edited by wanderer; Dec 20th 2017 at 05:07 PM. Reason: correct spelling ofmember's name
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