# A Train, Three Clocks, and an Observer

Discussion in 'Physics & Math' started by Motor Daddy, May 14, 2010.

1. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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If the train has a velocity, there will be two different transit times. How do you reckon that with the fact that you are midway between the two clocks, since light travel time defines distance?

So you took a piece of string and ran it from one end of the train to the other, cut it to the exact length, and then folded it in half so the ends lined up and cut it at the fold, to have two equal pieces of string. You take one string and start it at one end, and sit at the other end of the string, and whala, you are at the midpoint of the length of the train. If the transit time of light takes a different amount of time to go from the middle to each end, how do you justify your midpoint position, since light travel time defines distance?

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3. ### rpennerFully WiredValued Senior Member

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You seem deeply confused on this issue. The commercially available ring laser gyroscopes (and related fiber-optic gyroscopes) do not, as in diagram 1, have the sun at their center. You must go further down the page to the calculation for an arbitrary rigid light path, and discover that the location (or distance to) the center of rotation does not appear in the final calculation, but that the effect is proportional to the rate of change of angle, $\omega$ and the (signed) area enclosed by the rigid light path.

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5. ### phytiRegistered Senior Member

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You are talking one way paths which are different, but the synch convention uses both out and back times. The path lengths forward equal those backward, but in the opposite order.

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7. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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So you take a round trip time of light travel and divide it in half to come to the conclusion that light traveled the same time there and back, while disregarding the fact that the "mirror" placed at the end could have moved in the same direction of travel as the light during light travel towards it, until it impacts the mirror, and then disregard the fact that the mid point could be moving towards the returning light? That is too funny. You take a round trip time of travel and assume that the light traveled the same time there and back, and then have the nerve to say the train was at rest? You take an average and say, see, they are the same!

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How much time did it take the light to impact the end, and how much time did it take to impact the midpoint? The distance is not an average, it is light travel time.

So in effect, what you are saying is that if I drive 1 hour to a point, and turn around and drive .5 hours in the opposite direction, I actually drove .75 hours there and .75 hours back. If my speed was always 60 MPH, I drove 45 miles each way? That is absurd!

8. ### Jack_BannedBanned

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I am guessing the gyroscopes do not use the earth's radius as their radius either.

Let's look at math pages.

http://www.mathpages.com/rr/s2-07/2-07.htm

If two pulses of light are sent in opposite directions around a stationary circular loop of radius R,

Thus, the radius for the calculation of the earth's orbital sagnac is the distance of the sun to the earth.

The earth's rotational sagnac radius is the earth's radius.

The gyroscope's rotational sagnac radius is the gyroscope's radius.

See how that works.

Now, if you use angular velocity, then you must use the area swept out by the radius of the loop of the path.

I would hate to make such a silly public error. Perhaps, you should debate someone else.

As such, my contention that the orbital sagnac sould be greater than the rotational sagnac is valid.

9. ### Jack_BannedBanned

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You are simply not getting their position.

They believe light is relative to the frame.

You do not.

They think you look silly with your contention and you continue to repeat your argument in different ways in which they cannot ever see.

Again, they believe light is relative to the frame, ie c to the frame.

Then, the relativity postulate asserts each frame will apply the same rules of physics and hence, light is c to all frames.

10. ### phytiRegistered Senior Member

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329
-In the drawing, M is at the midpoint with his M-clock, the B-clock at
the back, the A-clock at the front, and moving to the right in the x
direction.
The clocks are synchronized with the B-clock ahead of the M-clock by t/2,
and the M-clock ahead of the A-clock by t/2, with t equal to the time for
light to travel out and back along d. It's obvious the time out is
different from the time back, as observed by anyone NOT moving with M.
The purpose of defining simultaneity and a practical method to establish
it, is to provide a consistent method of measurement for all observers in
motion, knowing only their relative speed in space. The method allows M
to consider his reference point as equivalent to the fixed reference frame.

Consider any container with M inside, moving at v relative to earth.
Everything in the container has a parallel translation of v. Whatever
motions occur in the container are going to include this translation, but
since this translation does not change the relative postions of any
objects inside, it's not detectable. Only change can be detected, but
uniform motion does not change.
If M sends simultaneous signals to A and B, and receives simultaneous
signals from A and B, and both clocks read the same time, then M
concludes they are equally distant and in synch, i.e., his frame is
symmetrical as a fixed frame should be.
Using this simultaneity convention does not imply the frame is not
moving, it just transforms it to an equivalent or pseudo rest frame.

-That's what you are saying, but you're correct.
You traveled 1.5 hr @ 60 mph = 90 miles.
The trips are equivalent, i.e., 60 + 30 = 45 + 45.

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11. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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Synchronized clocks beat as one. There is no time difference between synchronized clocks, regardless of how far apart they are.

The synchronization method you speak of is entirely wrong. If I synchronize three clocks and place one clock at B, one clock at A, and one clock at M, all three clocks beat as one. Given that fact, if you were at M, and a light signal was sent from A and B simultaneously, if all the clocks had an absolute zero velocity the light signals would arrive at M simultaneously. If those light signals had a time stamp of when they were sent, they would both have the same exact time stamp. When they arrived at M, M would also note the time of arrival, which would be at a later time then the time stamps from A and B. The difference between the departure time stamp and the arrival time stamp is the time of travel.

No clock is set ahead of the other, they are all synchronized clocks beating as one. The way it is supposed to work is that if every point in the universe has a synchronized clock, the time is exactly the same every place in the universe. The universe has one "timezone", if you will. Same as the concept of the Eastern timezone on the East coast. There is distance between Florida and NY, but the time is exactly the same. That's the way it's supposed to be everywhere in the universe. Universal time. There is supposed to be ONE timezone for a UNIverse.

Last edited: May 22, 2010
12. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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Going 60 miles in one direction and 30 miles in the opposite direct is not equal to 45 miles in one direction and 45 miles in the opposite direction. Are you even understanding what you are saying?

I said:

I specially said I drove 1 hour to a point and .5 hours in the opposite direction. I didn't say I drove .75 hours one way and .75 hours the other way. Are you now telling me what I did?

Here's a test, drive 60 miles in drive (forward), and then throw it in reverse and drive 30 miles and see if you end up in the starting position. Now drive 45 miles in drive and 45 miles in reverse. How can you possibly say those two situations are equal??

Last edited: May 22, 2010
13. ### Jack_BannedBanned

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How do you define points in the universe?

Further, the earth's motion in orbit is not picked with GPS.

Your argument says it should be.

Tell me I am wrong.

14. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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Light is emitted from a source in the universe. The light sphere expands independent of what the source does. At 1 second the sphere has a radius of ~186,000 miles. If the source moved during that one second, it is no longer at the center point of the light sphere. Just because the source moves doesn't mean there isn't a center point of the sphere. The sphere keeps expanding from the point in space it was emitted, independent of what the source does. The sphere's center will always be the point in space where the sphere's light originated, and the light will travel away from that point at c, independent of all other motion. Light simply travels at c relative to space.

Last edited: May 23, 2010
15. ### phytiRegistered Senior Member

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329
Motion alters the rate of a clock (time dilation). If you synch your clocks, then move them to a designated location, they aren't in sych anymore.
Google 'time dilation' and see how it works.

If I knew this topic was going to last this long, I would have brought tea and tarts!

16. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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Let's just use one timezone for an example, the Eastern timezone. Once you get the idea, you will know how distance, time, and clocks work, and then you can transform that concept to a universal scale using a universal timezone.

NY and Florida are in the same timezone, so theoretically all watches and clocks in NY and Florida remain in sync at all times. If you are in Florida, you can look at your watch and know EXACTLY what time it is 1,000 miles away in NY. EXACTLY, as the clocks remained synchronized at all times. If you were standing in Virginia (which is also synchronized with Florida and NY, because it too is in the Eastern timezone) you could look at your watch and know what exact time it is in NY and Florida. But say you were in Virginia and once your clock struck 12:00:00:00 there was a light signal sent from Florida. You know since your clock says 12:00:00:00 and the Florida time is synchronized to your watch, that the signal is on its way to your location. It takes time for light to travel, so it doesn't arrive at 12:00:00:00, it arrives at a later time.

Agreed so far?

17. ### rpennerFully WiredValued Senior Member

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Either you misuse the scientific sense of the word theory or you have not a clue about the way things work in our universe.

That's a god-awful theory, easily refuted by any of:
1) clocks which are not orginally synced with the standard (lazy out-of-towners, people who set their clocks ahead, etc.)
2) clocks which don't keep even time (sundials, wristwatchs, etc)
3) precise and accurately synced clocks which don't account for capricious and arbitrary changes to the standard (like daylight savings time and the nefarious leap second)
4) precise and accurately synced clocks which are in motion with respect to the reference
5) precise and accurately synced clocks which are at a different altitude than the reference

You aren't addressing the physics. You aren't even addressing the engineering realities of the man-made fiction of a time zone.

18. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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Yeah, it isn't the same time in NY and Florida because Grandma forgot to put new batteries in her wall clock, junior's watch doesn't work in the pool, and Jethro never adjusted his clock for daylight savings time.

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However in spite of those ridiculous statements, synchronized clocks beat as one, and light takes time to travel. Facts that can't be refuted.

You want to address physics properly? We don't live in a vacuum. No matter how much you scream and holler insisting your train is at rest, you will travel a distance and it will take time, and you will start at one point and end at another point. You can proclaim to be at rest on the highway, but if the guy in front of you slams on the brakes you are going through the windshield if you aren't wearing your seat belt! You can demand all you want that the Earth is at rest, but we both know you are wrong, don't we?

19. ### AlphaNumericFully ionizedRegistered Senior Member

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Why is this thread still open? Neither Jack nor MD have any interest in learning from their mistakes and both have made it clear they firmly believe its everyone else's fault but theirs, with MD going so far as to basically deny experimental fact. I have considerably less time to spend on forums due to actually having a real job now but even if I had a week long holiday they aren't worth the time. Rpenner, phyti, your time is worth more than this.

20. ### Jack_BannedBanned

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1,383
What?

All my logic has left you submissive.

My twins thread was never refuted.

When in the time of the stationary frame does the moving frame see light a distance r.

Is there an answer?

I know the answer do you?

21. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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To sum this thread up, The OP is correct, and the reason the relativist can't see it is because they don't understand what synchronized clocks are because of Einstein's incorrect synchronization method, and the fact that there is no relativity of simultaneity. Is it any wonder that relativity has so many paradoxes. Just to be clear, a paradox is an indicator that something is not right.

22. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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I mean, if you synchronize three clocks, and start walking from a midpoint of a train at exactly 12:00:00, walk for one second to one end of the train and place a clock there, it is 12:00:01. If you then leave that position when all the clocks read 12:00:07 and walk to the other end of the train, and it takes you two seconds to get there, and place a clock there, the two clocks read 12:00:09. If you leave there at 12:00:33 and go to the midpoint of the train, and it takes you one second to get there, your clock reads 12:00:34 when you get there. All the clocks are in sync, and have remained in sync the entire time.

However, the fact that the midpoint is an equal distance away from each end clock means that the light from each end clock will take time to travel to the midpoint, so if it leaves each end at 12:00:57, it will arrive at the midpoint at a later time, as light takes time to travel. This can be verified by time stamping the light signals of the departure time they left the endpoints, and the arrival time at the midpoint. It is an absolute fact.

23. ### funkstarratsknufValued Senior Member

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Just to be clear, you do realize that there aren't any paradoxes there, right?

I second AN - this thread should have been an abortion, but euthanasia will do.