Reply Mon 5 Jan, 2015 12:48 pm
Setting aside for the time being my crazy notions about time-at-a-distance, the mass of the photon, and what might happen if Einstein were wrong....

http://able2know.org/topic/263375-1

.....let's consider her voyage in terms of classical (Special) relativity. Sister Marty's trip from her home planet to visit us here, has gotten complicated, deserves its very own thread in order to address a2k respondent Bran's very pertinent objection [as well as Para's, Con's, and others'] concerning our view of her trip compared to hers. But first some background:

All clocks in our immediate Universe not in significant motion with respect to one another had previously been synchronized, presumably very tediously, supposedly by radio and our scenario takes place with Mars at a distance of ten light minutes. Marty has a very sturdy backbone, as you will see, and a ship that can withstand the most extreme acceleration.

In order to provide an avenue for such acceleration she had earlier traveled to her moon Phobos, where she has breakfast before taking off at 11:50, passing her home base in our direction at (nearly) velocity c, her hand on the tiller and her beautiful little mouth wide open in yawn. Owing to dilation, to her the entire trip is of course very short indeed, observing out the front window of her ship your watch and mine to jump ahead almost instantaneously from a reading of 11:40 to 12:00 as she arrives here at noon, hers still reading 11:50 because of course it's only a wristwatch.

[As a side note, Bran, it's important to acknowledge that in order to visit us she has to pass through two 10-minute passels of photons. Keep this firmly in mind throughout.]

[However, backtracking just a bit we can suppose she might also have on board an atomic clock of some sort, and that she's very quick-witted so that she's able to watch the advance of that "quick jump" in a more leisurely fashion. So halfway through her trip when she notes through the front window a reading of 11:50 on our watches, she glances out a side window and notes the reading of a clock we had placed on a convenient asteroid,....

http://www.answers.com/Q/What_is_a_rock_floating_in_space_called

.....also 11:50...]

But now Para brings up a very pertinent point, for which I thank him, however much more complicated that makes my description of Marty's excursion. I've described Marty's perception of our watches (that is of Earth humanoids you and me) as a "jump", [represented also by that quick advance in the reading of her on-board atomic timer]. It's here that Para, very logically and in absolute pertinence, objects to my description on the grounds that two observers passing one another in the night each notes the other's clock to run slower, where apparently I've noted Para's observation implying instead a very rapid advance.

Bran, Para, the discrepancy here, partly semantic, partly misunderstanding of terms,

http://able2know.org/topic/263375-9#post-5853178

.....two trains passing one another in the night not quite the same situation because in our account Marty's acceleration throws a monkey wrench into the works. But resolved by the observation that Marty and I can indeed observe the other's clocks as (almost) stopped, just as the two choo-choo passengers see the other train's clock apparently running abnormally slow. So let me elaborate:

Of course it's acknowledged by both sides of the discussion that we'd see Marty's watch as (virtually) stopped [that is of course after she'd arrived; but let's not complicate things further] yet if ours also stops (to her) how do we account for her apparent observation of its rapid advance?

Answer: Unlike the situation of the trains, one of our participants (Marty) had accelerated, giving her the illusion of an instantaneous jump in our time. In fact, supposing of course Marty is just as smart as we and understands special relativity, she knows at launch that (to her) our watches now read noon...

....confirmed for instance if we then assume she doesn't stop here but swishes on past us, with a really quick mutual "hi." When she looks out the rear window of her ship and sees us receding, you and I do now appear frozen in place. Indeed to her, looking back with her marvelous telescope, days or weeks later she still sees us standing there with arms up in valiant salute

....whereas some of us (not necessarily me) interpret her foregoing observation as owing merely to the fact that she's keeping up with the photons that left our bodies in salute. (Do keep this in mind for my closure.) In any case, the illusion has been conquered and now she does in fact see us as (for all present purposes) stationary. So Para there's no basic discrepancy in the principle represented by the trains and that of Marty's trip as I'd described it.

That ends the basic story, which I hope was of help (that's assuming of course I'm not dead wrong). Perhaps I'll find an expert somewhere we can ask.


[However, at this point the otherwise casual reader (you? with us standing there together telescopes in hand) may chime in with, "But Dale, it's Marty who's really rigid, there, swishing by with her mouth open and clock stopped at 11:50, whereas her observation is illusory cause we all know it's the participant who accelerates whose watch really stops."

Well I (Dale) wish, a2k helper, you hadn't breached this possibility because it gets into the validity of "stationary reference" to which all motion can supposedly be compared and the suggestion that, well, a2k fellas, it's all relative so how do we know it's not us (and our little corner, the visible part, of the Universe) that isn't in motion at (almost) c, and that in her catapult from Phobos Marty had come to a standstill. With your supposition--even though no diff in our respective observations--it's us not her who's really stopped. It's just that our brains being (nearly) stopped too, we have the impression that time's passing at its usual pace.

So guys, stay with me, we have two independent accounts here, the first concerning Marty's flight and the second (the two paras immediately above), whether or not it might be permissible for us in effect to "switch places" with Marty. I hope you might address the first account if you like, herewith; but for the second, being even more involved, let's have in a new thread.


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parados
 
  1  
Reply Mon 5 Jan, 2015 01:46 pm
@dalehileman,
That's part of why it's called relativity. The observation is relative to the observer which is why the 2 observers see different things under relativity.


Quote:

[As a side note, Bran, it's important to acknowledge that in order to visit us she has to pass through two 10-minute passels of photons. Keep this firmly in mind throughout.]
That is nonsense. You might as well ask that we keep in mind that 3 monkeys juggled 12 bananas. It would make as much sense.
dalehileman
 
  1  
Reply Mon 5 Jan, 2015 02:06 pm
@parados,
Quote:
…..called relativity. ….. relative to the observer which is why the 2 observers see different things…...
Yes Para thanks but I understand that. Where have I ever posted anything to the contrary

Quote:
….. she has to pass through two 10-minute passels of photons…….

Quote:
...You might as well ask that we keep in mind that 3 monkeys juggled 12 bananas…...
Let me see if I can summarize:

She and we had earlier synced and agreed on her takeoff time of 11;50, when she's reading our watch as 11;40, obviously 'cuz it took 10 minutes for its image to get there. Since she's travels at a velocity c and our planets are 10 light minutes apart, it's apparent she must arrive at noon. That's 12:00 minus 11:40 or 20 minutes of photons

I can't see where the confusion is arising
parados
 
  1  
Reply Mon 5 Jan, 2015 02:08 pm
@dalehileman,
Quote:
where apparently I've noted Para's observation implying instead a very rapid advance.
Where did I say that?
parados
 
  1  
Reply Mon 5 Jan, 2015 02:17 pm
@dalehileman,
Quote:
She and we had earlier synced and agreed on her takeoff time of 11;50, when she's reading our watch as 11;40, obviously 'cuz it took 10 minutes for its image to get there. Since she's travels at a velocity c and our planets are 10 light minutes apart, it's apparent she must arrive at noon. That's 12:00 minus 11:40 or 20 minutes of photons


She doesn't pass through 20 minutes of photons. Time changes because of her speed relative to earth. You keep trying to use the observation from a different velocity. You can't do that. It violates relativity.
dalehileman
 
  1  
Reply Mon 5 Jan, 2015 02:29 pm
@parados,
Quote:
where apparently I've noted Para's observation implying instead a very rapid advance.
Quote:
Where did I say that?
That's what I inferred you meant; note my use of the term "implying"

According to the article about the trains I had supposed that you were speculating that during her 10-min trip instead of a 20-min jump in our watch she would view it as stuck at noon. You'll have to reread my OP, which maintains that she wouldn't view us as stationary until she has passed by

I will concede however that she's unlikely to be so quick-witted as to actually sense her travel time. Therefore for all practical purposes yes, when she fires her rocket, leaving home at (well, very very close to) c, her perception of the reading of our watch mistakenly has it stuck at 12:00 all the way

Sure Para I could be dead wrong but how, where exactly
0 Replies
 
dalehileman
 
  1  
Reply Mon 5 Jan, 2015 02:48 pm
@parados,
Quote:
She doesn't pass through 20 minutes of photons.
Para she hasta

Quote:
Time changes because of her speed relative to earth.
Sure, at takeoff her watch stops (almost) [Tho by our reckoning to be sure]

Quote:
You….use the observation from a different velocity…...violates relativity
Not at all. For simplicity and because I thought you might not believe it, what I hadn't mentioned was that the firing of her rocket made us instantly come much closer (by her reckoning)

Much, much closer, depending of course on how near to c her velocity. The two parcels of photons seem crowded into maybe a half mile, maybe four inches. Of course understanding Al she realizes this distance is "really" ten light minutes. Not a violation of our physicist's theory at all


But now we're getting back into "stationary reference," that I had hoped to avoid for the time being, with whose clock "really" stopped supposedly the traveler who accelerated (again not my supposition; one or two other a2k'ers had suggested it)

So as far as special reltivity goes, maybe if you peruse my OP it might become clearer

But again thanks for the chat, it has made me really think about Al's contribution to phsics
parados
 
  1  
Reply Mon 5 Jan, 2015 02:53 pm
@dalehileman,
dalehileman wrote:

Quote:
She doesn't pass through 20 minutes of photons.
Para she hasta


No, she doesn't.

If earth sees the trip as lasting 10 minutes then she would also see the trip as lasting 10 minutes. That is what relativity says.
dalehileman
 
  1  
Reply Mon 5 Jan, 2015 02:58 pm
@parados,
Quote:
she would also see the trip as lasting 10 minutes.
Being familiar with the theory she knows that by our reckoning the trip does indeed take ten minutes. However owing to dilation she senses it as instantaneous

Quote:
That [seeming 10 minutes] is what relativity says
Not as I learned it
parados
 
  1  
Reply Mon 5 Jan, 2015 03:11 pm
@dalehileman,
Wrong. Go read the example again.
dalehileman
 
  1  
Reply Mon 5 Jan, 2015 04:12 pm
@parados,
Quote:
Wrong. Go read the example again.
Okay Para but please provide a link won't you
parados
 
  1  
Reply Tue 6 Jan, 2015 09:09 am
@dalehileman,
I've provided the link twice now. If you didn't understand it the first 2 times, why don't you book mark it to keep it for reference?

http://en.wikipedia.org/wiki/Theory_of_relativity
http://en.wikipedia.org/wiki/Time_dilation

The thing you don't seem to understand is the person in the space ship sees the earth moving at near c speed so the rules of time dilation apply to their view of the earth's clocks. There is no near c speed from a personal point of view because you can never achieve it in your own frame of reference. Only other frames of reference can see that.
dalehileman
 
  1  
Reply Tue 6 Jan, 2015 11:38 am
@parados,
Quote:
I've provided the link twice now...
Thanks Para for your patience but I'm familiar with those basics. It might help if you were to provide a link or two from my postings where I seem to disagree with current theory, then show me exactly where in those above links my assertions disagree

Quote:
The thing you don't seem to understand is the person in the space ship sees the earth moving at near c speed so the rules of time dilation apply to their view of the earth's clocks
To the contrary Para I had supposed I do understand, and indeed it does, as I thought I had explained maybe two or three times above

As I had said, to Marty the apparent rush in the reading of our watch owes to her acceleration from Phobos, puzzling to some because it evidently conveys the mistaken impression that dilation isn't working. But remember, Marty can't possibly confirm the effect of her velocity on the appearance of Earth clocks until she's actually here. Because she's coming toward us at the same velocity (nearly) c that our image at 12:00 is traveling toward her, then she has almost arrived before she encounters it

However, after she's passed, as I supposed I had recently explained above, she can now look back when in agreement with what she had read about relativity, we now appear stationary, arms still raised in salute. Once you've grasped this fundamental you'll see I'm not in any way in conflict with old friend Al

Still, with apologies to the rest of ya who had more readily absorbed my OP, just how long it is before Marty sees my hand to start to drop depends entirely on how close to c her velocity, incidentally the same length of time before we see her mouth begin to close

I can only guess Para that owing possibly to your status as esl if not my incompetence describing the effects of relativity, our apparent disagreements might owe entirely to semantic difficulties


Anybody else, help, help
…forgiving any evident typos as I have to rush off to the Br
parados
 
  1  
Reply Tue 6 Jan, 2015 11:43 am
@dalehileman,
Quote:
Because she's coming toward us at the same velocity (nearly) c that our image at 12:00 is traveling toward her, then she has almost arrived before she encounters it

No, she's not. Light is traveling at c for her. You are using an outside reference to try to explain her reference. That is a no no when it comes to relativity.
parados
 
  1  
Reply Tue 6 Jan, 2015 12:19 pm
@dalehileman,
It's difficult to understand because it's so counterintuitive.

Let's blow your mind dale.
Marty has a passenger named Barney. They are 10 light minutes from earth where Ann and Sharon are. They all synchronize their watches keeping in mind the 10 minute communication lag. Marty and Barney see Ann and Sharon's watches at 11:40 when theirs read 11:50. Ann and Sharon see Marty and Barney's watches as reading 11:40 when theirs read 11:50.

Now if we magically are able to accelerate Marty and Barney to nearly the speed of light it will take about 10 minutes for them to get to earth. The speed of light is still the same for Marty and Barney so they will see the trip as taking 10 minutes and their watches will tick off 10 minutes. Ann and Sharon will see the trip as taking 10 minutes and their watches will tick off 10 minutes. As Marty goes by Earth at nearly the speed of light Barney and Ann switch places. Barney suddenly decelerates to Earth's speed and Ann suddenly accelerates to Marty's speed.

When Ann and Barney switch their reference point, this is what happens.
Marty's watch would read 12:00 and Ann's would read about 11:50 on the spaceship going nearly the speed of light.
Sharon's watch would read 12:00 and Barney's would read 11:50 on earth.
parados
 
  1  
Reply Tue 6 Jan, 2015 12:21 pm
@dalehileman,
Quote:
But remember, Marty can't possibly confirm the effect of her velocity on the appearance of Earth clocks until she's actually here. Because she's coming toward us at the same velocity (nearly) c that our image at 12:00 is traveling toward her, then she has almost arrived before she encounters it

This is what you get wrong. Marty doesn't see himself going at the velocity of c. He sees earth hurtling toward him at c. He can see each minute that transpires on earth because for him he is motionless in comparison to the speed of light.
dalehileman
 
  1  
Reply Tue 6 Jan, 2015 12:43 pm
@parados,
Quote:
No, she's not. Light is traveling at c for her
I didn't mean to infer that our wavefront, eg conveying a reading of 11;40 as it passes her ship at takeoff, won't be clocked at c. Of course her mother resting at home base finds it passing at c but Marty swishing past overhead also finds it passing her ship at (nearly) c; all in agreement with you and Al

Where Para your misunderstanding arises probably involves your interpretation of my observation suggesting both parcels apparently pass at a velocity 'way exceeding c. But remember that when she fires her rocket, Earth instantly jumps closer so that both parcels (11:40 to 12:00) are squeezed into an intervening distance of, say, 14 inches; thus she too measures their velocity at exactly c because the tiny discrepancy is probably beyond the capability of her instruments

Para you needn't read the following para because it doesn't really impinge upon our present chat

I'll be first to admit incidentally that the idea of a huge planet accelerating to a velocity that in a few microseconds takes it 10 light minutes through space to within a few feet of Mars is very hard to accept, probably by many of us

So we (tho not me necessarily) respond: But isn't Earth's apparent jump entirely illusory, that Earth remains at 10 light minutes throughout. The risk here, however, is that we might be introducing a sort of stationery reference, the existence of which is scrupulously denied by the Relativists who respond, "All right then, let's assume that it's not Marty but the Earth (and immediate visible environs) in motion and that Marty firing her rocket brings her to a standstill with respect to that so-called ref

….so that we are really 32 inches from Mars, that our 10 light min is what's illusory" ????

To all: Those last two paras are getting pretty deep so I'll be first to acknowledge the possibility that I'm dead wrong, hence the ?????'s. Still the idea of the stationary ref remains very persistent……and might even be addressed…by somebody a whole lot smarter than I….in a new thread
parados
 
  1  
Reply Tue 6 Jan, 2015 12:54 pm
@dalehileman,

Quote:
….so that we are really 32 inches from Mars, that our 10 light min is what's illusory" ????
Again, you assume that light travels at a different speed in a different reference point. It does not. If the earth is traveling at nearly c compared to another reference point the earth would still be 10 light minutes from Mars on our reference simply because that is our reference point.
contrex
 
  1  
Reply Tue 6 Jan, 2015 12:56 pm
Let me get this straight, Dale. You're saying that Mars is really 32 inches from Earth?
dalehileman
 
  1  
Reply Tue 6 Jan, 2015 01:06 pm
@parados,
Quote:
…. accelerate Marty and Barney to nearly the speed of light it will take about 10 minutes for them to get to earth
Yes Para, right, 10 min, but that's by our watch not theirs. By theirs they they arrive almost instantly, still reading 11:50

Skirting reference to that doggone stationary ref, remember after they arrive and (in retrospect) we can view the entire proceeding we find that their watch stopped at 11;50 and remains at that reading throughout. It won't be for eg 3.5 quadrillion years that 'way off in the distance (in the direction they're still headed) we finally see it reading 12:00

Of course we can say the same about their view of ours, then requiring the same period to advance from 12:00 to 12:10

I think we'll find the passenger swap irrelevant, unnecessarily complicating the event

 

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