Earlier or later

Sep29-04, 08:31 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','to olbar=no,location=no,scrollbars=yes,resizable=yes, status=no,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usene t ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Two identical events occur very close by in time(at\nroughly the same location)--consider e.g. emission of\n2 identical photons by an assembly of atoms.The time\ndifference between the emissions is exceedingly\nsmall(say ten to the power minus twenty seconds).\nThe question is:-can we say with certainty which\nphoton is emitted earlier and which later?If not what\ndoes this imply?\nJagmeet\n\nP.S. New thread\n\n\n\n__________________________________\n Do you Yahoo!?\nNew and Improved Yahoo! Mail - Send 10MB messages!\nhttp://promotions.yahoo.com/new_mail\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Two identical events occur very close by in time(at
roughly the same location)--consider e.g. emission of
2 identical photons by an assembly of atoms.The time
difference between the emissions is exceedingly
small(say ten to the power minus twenty seconds).
The question

say with certainty which
photon is emitted earlier and which later?If not what
does this imply?
Jagmeet

P.S. New thread

__{________________________________}
Do you Yahoo!?
New and Improved Yahoo! Mail - Send 10MB messages!
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Sep29-04, 12:18 PM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','to olbar=no,location=no,scrollbars=yes,resizable=yes, status=no,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usene t ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n"Jagmeet Singh" <jagmeetus@yahoo.com> wrote in message\nnews:20040929113552.9982.qmail@web21005.m ail.yahoo.com...\n> Two identical events occur very close by in time(at\n> roughly the same location)--consider e.g. emission of\n> 2 identical photons by an assembly of atoms.The time\n> difference between the emissions is exceedingly\n> small(say ten to the power minus twenty seconds).\n> The question is:-can we say with certainty which\n> photon is emitted earlier and which later?If not what\n> does this imply?\n> Jagmeet\n>\n> P.S. New thread\n\nIn non-relativistic (NR) theory of Thomson scattering, only the\n1st-order AA "seagull" Feynman graph (simultaneous absorption and\nemission) is taken into account. In the (more accurate) relativistic\ntheory, on the other hand, that seagull graph is replaced by two graphs,\nin each of which photons are absorbed and emitted one at a time. One of\nthe graphs has absorption first (in time), the other has emission first.\n\nJohn Lowry\nFlight Physics\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Jagmeet Singh" <jagmeetus@yahoo.com> wrote in message
news:20040929113552.9982.qmail@web21...yahoo .com...
> Two identical events occur very close by in time(at
> roughly the same location)--consider e.g. emission of
> 2 identical photons by an assembly of atoms.The time
> difference between the emissions is exceedingly
> small(say ten to the power minus twenty seconds).
> The question

say with certainty which
> photon is emitted earlier and which later?If not what
> does this imply?
> Jagmeet
>
> P.S. New thread

In non-relativistic (NR) theory of Thomson scattering, only the
1st-order AA "seagull" Feynman graph (simultaneous absorption and
emission) is taken into account. In the (more accurate) relativistic
theory, on the other hand, that seagull graph is replaced by two graphs,
in each of which photons are absorbed and emitted one at a time. One of
the graphs has absorption first (in time), the other has emission first.

John Lowry
Flight Physics

Sep30-04, 01:46 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','to olbar=no,location=no,scrollbars=yes,resizable=yes, status=no,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usene t ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nJagmeet Singh <jagmeetus@yahoo.com> wrote in message news:<20040929113552.9982.qmail@web21005.mail.y ahoo.com>...\n> Two identical events occur very close by in time(at\n> roughly the same location)--consider e.g. emission of\n> 2 identical photons by an assembly of atoms.The time\n> difference between the emissions is exceedingly\n> small(say ten to the power minus twenty seconds).\n> The question is:-can we say with certainty which\n> photon is emitted earlier and which later?If not what\n> does this imply?\n\nFirst, orient your x axis so that it runs from one event\'s\nspace location to the other. This reduces the entire thing\nto one space dimension and one time dimension.\n\nThe test is quite straightforward. If the distance between\nthe events is smaller than the distance light can travel\nin the time between the events, the events are called\ntime-like-separated.\n\n|x1 - x2| < c |t1 - t2| => time-like\n\nIf the distance is larger then they are space-like-sep.\n\n|x1 - x2| > c |t1 - t2| => space-like\n\nIf the distance is identical then they are null-separated.\n\n|x1 - x2| = c |t1 - t2| => null\n\nSpace-like means they cannot be uniquely ordered in time.\nTime-like or null means they can.\n\nAnother way to think of it: If light can get from one\nevent to the space location of the other event, and do\nit no later than the other event happens, then this\nestablishes the time ordering. The event light can\nstart at is before, the event light can finish at is after.\ngrelbr\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Jagmeet Singh <jagmeetus@yahoo.com> wrote in message news:<20040929113552.9982.qmail@web2...aho o.com>...
> Two identical events occur very close by in time(at
> roughly the same location)--consider e.g. emission of
> 2 identical photons by an assembly of atoms.The time
> difference between the emissions is exceedingly
> small(say ten to the power minus twenty seconds).
> The question

say with certainty which
> photon is emitted earlier and which later?If not what
> does this imply?

First, orient your x axis so that it runs from one event's
space location to the other. This reduces the entire thing
to one space dimension and one time dimension.

The test is quite straightforward. If the distance between
the events is smaller than the distance light can travel
in the time between the events, the events are called
time-like-separated.

time-like

If the distance is larger then they are space-like-sep.

space-like

If the distance is identical then they are null-separated.

null

Space-like means they cannot be uniquely ordered in time.
Time-like or null means they can.

Another way to think of it: If light can get from one
event to the space location of the other event, and do
it no later than the other event happens, then this
establishes the time ordering. The event light can
start at is before, the event light can finish at is after.
grelbr

Oct26-04, 12:54 PM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','to olbar=no,location=no,scrollbars=yes,resizable=yes, status=no,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usene t ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Jagmeet Singh wrote:\n> Two identical events occur very close by in time(at\n> roughly the same location)--consider e.g. emission of\n> 2 identical photons by an assembly of atoms.The time\n> difference between the emissions is exceedingly\n> small(say ten to the power minus twenty seconds).\n> The question is:-can we say with certainty which\n> photon is emitted earlier and which later?If not what\n> does this imply?\n> Jagmeet\n>\n\nSeems to me you are trying to violate the uncertainty principle when you\nset up the probably. If you know the timing of the photons in such\nprecision then you will have a hugh uncertainty in their energy.\nTherefore, how can you claim that they are identical photons?\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Jagmeet Singh wrote:
> Two identical events occur very close by in time(at
> roughly the same location)--consider e.g. emission of
> 2 identical photons by an assembly of atoms.The time
> difference between the emissions is exceedingly
> small(say ten to the power minus twenty seconds).
> The question

say with certainty which
> photon is emitted earlier and which later?If not what
> does this imply?
> Jagmeet
>

Seems to me you are trying to violate the uncertainty principle when you
set up the probably. If you know the timing of the photons in such
precision then you will have a hugh uncertainty in their energy.
Therefore, how can you claim that they are identical photons?

**gptejms** · Oct28-04, 01:28 PM

Originally Posted by anuj

As long as there is no correlation between the wavefunctions of two photons in the time domain, we can say with certainity as to which photon was emitted earlier and which one later. The problems may arise if there is correlation.

anuj,one does talk of correlations between electric fields(not wavefunctions) at two points r1,t1 and r2,t2 (when one discusses optical coherence) but this says nothing of which photon is where or how many photons there are in the first place.Moreover the fields are not of this photon or that photon--it's just one field.You may also like to look at another thread by the same title 'Earlier or later' --a part of the discussion is there and a part here.

**gptejms** · Oct28-04, 01:28 PM

Originally Posted by Joseph.D.Warner

Seems to me you are trying to violate the uncertainty principle when you
set up the probably. If you know the timing of the photons in such
precision then you will have a hugh uncertainty in their energy.
Therefore, how can you claim that they are identical photons?

If your argument is right then there should never be such closely spaced identical photons emitted by any source.But in any monochromatic source photons(identical) are being emitted by excited atoms at random intervals of time--and these intervals could be very tiny.

**anuj** · Nov3-04, 09:43 AM

[quote=Jagmeet Singh]<consider e.g. emission of
2 identical photons by an assembly of atoms.The time
difference between the emissions is exceedingly
small(say ten to the power minus twenty seconds).
The question

say with certainty which
photon is emitted earlier and which later?If not what
does this imply?
Jagmeet

As long as there is no correlation between the wavefunctions of two photons in the time domain, we can say with certainity as to which photon was emitted earlier and which one later. The problems may arise if there is correlation.