Science > Physics > What an odd way to hold a discussion... question follows
| Topic: |
Science > Physics |
| User: |
"Edward Green" |
| Date: |
25 Sep 2006 09:40:07 PM |
| Object: |
What an odd way to hold a discussion... question follows |
I know complaining about the awful injustice of it all only makes me
more of a crank, but...
Essaying to write to sci.physics.research, I was successful in starting
in a thread, but unable to reply because I am asked for a "citation"
for a randomly chosen proper name, and honestly reply it was a randomly
chosen name, and why do you think I need a "citation", with the
injunction "keep it civil"(!). I was unable to offer a possibility not
considered by other respondents with a sketch of the simple calculation
(being merely an integral) because I have "not done a calculation"(!),
although part of my motive in writing was in fact to ask for hints how
to perform simple calculations in GR.
Of course I can't help but wonder if the individual of the same given
name as one of the moderators who sometimes posts in
sci.physics.relativity and sci.physics is in fact the same individual,
in which case telling him he had no bloody idea what he was talking
about in that latter, uncivil, group -- which he didn't -- of course
gives license for whatever petty revenge he is able to extract by
virtue of whatever other positions of dubious authority he may occupy.
Not mentioning names.
Then again maybe I shouldn't have mentioned that my motivation in
learning to do some simple calculations involving the metric was to
accumulate circumstantial evidence for my hunch that nothing, in fact,
ever falls into a black hole -- by preponderance of the semantical
evidence of what we might like to mean by "ever" -- despite the one
piece of circumstantial evidence commonly offered that "does too fall
in", for which I already humbly hold what seems to me an effective
rebuttal.
But they can't stop me from ranting here... bwa ha ha ha ha!!!!
OK.
Maybe somebody happening to read this rant could outline the ansatz of
a calculation to answer the following question -- just outline how to
approach it, and I will struggle with the details:
The setup:
I drop, from a given static position above the event horizon, an unlit
rocket into a canonical Schwarzschild black hole. I hold in my hand a
universal IR rocket remote, with a button labeled "return". I point
the remote towards the falling rocket, press the button, and a light
pulse overtakes the rocket, instructing it to light off its motors,
save itself from oblivion, and return it to my position. A finite time
later I again hold the rocket in my hand.
The question:
How long can I wait before hitting the button so that the light pulse
will reach the rocket before it crosses the horizon in its own proper
time, signaling it to return? [Ignore how much thrust will be
required, and how blueshifted the signal will be when it reaches the
rocket.]
The possibilities:
Either the time available to hit the remote is finite or infinite. If
finite, this would be circumstantial evidence supporting the claim that
"does too fall in before the end of time": what we can no longer
prevent may perhaps as well have happened, even if we can't know just
when. If infinite, on the other hand, this would support the assertion
that the crossing event never happens -- an irreversible event which
can always be prevented from happening presumably never "happens".
Please help crankdom everywhere by any hints on how to perform the
calculation!
I especially appeal to the large and vibrant crank population in the
unmoderated groups, since, performing a correct calculation may give a
viable chance to show the experts wrong, wrong, wrong, bwa ha, ha...
and etc. -- at least the ones who insist that things do fall in before
aeternity. Learn how to do a calculation in GR! Prove experts wrong!
Have fun!
Anybody want to place bets on which way the calculation will go?
(Crow pie already cooling in pantry, just in case).
.
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| User: "FrediFizzx" |
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| Title: Re: What an odd way to hold a discussion... question follows |
25 Sep 2006 11:15:38 PM |
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"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1159238407.788715.89200@m73g2000cwd.googlegroups.com...
I know complaining about the awful injustice of it all only makes me
more of a crank, but...
Essaying to write to sci.physics.research, I was successful in
starting
in a thread, but unable to reply because I am asked for a "citation"
for a randomly chosen proper name, and honestly reply it was a
randomly
chosen name, and why do you think I need a "citation", with the
injunction "keep it civil"(!). I was unable to offer a possibility
not
considered by other respondents with a sketch of the simple
calculation
(being merely an integral) because I have "not done a calculation"(!),
although part of my motive in writing was in fact to ask for hints how
to perform simple calculations in GR.
If you think your reply was worthy, just post it here. Charter-wise,
relativity questions and comments are supposed to go s.p.relativity
group anywise.
Of course I can't help but wonder if the individual of the same given
name as one of the moderators who sometimes posts in
sci.physics.relativity and sci.physics is in fact the same individual,
in which case telling him he had no bloody idea what he was talking
about in that latter, uncivil, group -- which he didn't -- of course
gives license for whatever petty revenge he is able to extract by
virtue of whatever other positions of dubious authority he may occupy.
Not mentioning names.
They are not the same person.
FrediFizzx
Quantum Vacuum Charge papers;
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.pdf
or postscript
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.ps
http://www.arxiv.org/abs/physics/0601110
http://www.vacuum-physics.com
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| User: "Ken Muldrew" |
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| Title: Re: What an odd way to hold a discussion... question follows |
29 Sep 2006 01:03:02 PM |
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"Edward Green" <spamspamspam3@netzero.com> wrote:
I know complaining about the awful injustice of it all only makes me
more of a crank, but...
Essaying to write to sci.physics.research, I was successful in starting
in a thread, but unable to reply because I am asked for a "citation"
for a randomly chosen proper name, and honestly reply it was a randomly
chosen name, and why do you think I need a "citation", with the
injunction "keep it civil"(!). I was unable to offer a possibility not
considered by other respondents with a sketch of the simple calculation
(being merely an integral) because I have "not done a calculation"(!),
although part of my motive in writing was in fact to ask for hints how
to perform simple calculations in GR.
The guy who wanted a citation (Tessel) is Chris Hillman who used to
post extensively here on GR, information theory, and dynamical
systems, always giving a complete bibliography at the end of his
posts. His demands for a citation (and innuendo that such rough hewn
folk who neglect to give citations would have been kept well away from
the tea party in the good old days) were pretty funny, but not
terribly civil. I think you should have been allowed to respond in
kind. Anyway, I think Greg Egan cleared up the misunderstanding and
attempted to answer your question.
Sorry I don't have anything of substance to add.
Ken Muldrew
kmuldrezw@ucalgazry.ca
(remove all letters after y in the alphabet)
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| User: "Edward Green" |
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| Title: Re: What an odd way to hold a discussion... question follows |
07 Oct 2006 08:52:54 PM |
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Ken Muldrew wrote:
"Edward Green" <spamspamspam3@netzero.com> wrote:
I know complaining about the awful injustice of it all only makes me
more of a crank, but...
Essaying to write to sci.physics.research, I was successful in starting
in a thread, but unable to reply because I am asked for a "citation"
for a randomly chosen proper name, and honestly reply it was a randomly
chosen name, and why do you think I need a "citation", with the
injunction "keep it civil"(!). I was unable to offer a possibility not
considered by other respondents with a sketch of the simple calculation
(being merely an integral) because I have "not done a calculation"(!),
although part of my motive in writing was in fact to ask for hints how
to perform simple calculations in GR.
The guy who wanted a citation (Tessel) is Chris Hillman who used to
post extensively here on GR, information theory, and dynamical
systems, always giving a complete bibliography at the end of his
posts. His demands for a citation (and innuendo that such rough hewn
folk who neglect to give citations would have been kept well away from
the tea party in the good old days) were pretty funny, but not
terribly civil. I think you should have been allowed to respond in
kind. Anyway, I think Greg Egan cleared up the misunderstanding and
attempted to answer your question.
Sorry I don't have anything of substance to add.
Well, thank you for your reply, always appreciated.
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| User: "Ahmed Ouahi, Architect" |
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| Title: Re: What an odd way to hold a discussion... question follows |
25 Sep 2006 09:46:27 PM |
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All things may corrupt when minds are prone to evil.
-- Ovid
--
Ahmed Ouahi, Architect
Best Regards!
"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1159238407.788715.89200@m73g2000cwd.googlegroups.com...
I know complaining about the awful injustice of it all only makes me
more of a crank, but...
Essaying to write to sci.physics.research, I was successful in starting
in a thread, but unable to reply because I am asked for a "citation"
for a randomly chosen proper name, and honestly reply it was a randomly
chosen name, and why do you think I need a "citation", with the
injunction "keep it civil"(!). I was unable to offer a possibility not
considered by other respondents with a sketch of the simple calculation
(being merely an integral) because I have "not done a calculation"(!),
although part of my motive in writing was in fact to ask for hints how
to perform simple calculations in GR.
Of course I can't help but wonder if the individual of the same given
name as one of the moderators who sometimes posts in
sci.physics.relativity and sci.physics is in fact the same individual,
in which case telling him he had no bloody idea what he was talking
about in that latter, uncivil, group -- which he didn't -- of course
gives license for whatever petty revenge he is able to extract by
virtue of whatever other positions of dubious authority he may occupy.
Not mentioning names.
Then again maybe I shouldn't have mentioned that my motivation in
learning to do some simple calculations involving the metric was to
accumulate circumstantial evidence for my hunch that nothing, in fact,
ever falls into a black hole -- by preponderance of the semantical
evidence of what we might like to mean by "ever" -- despite the one
piece of circumstantial evidence commonly offered that "does too fall
in", for which I already humbly hold what seems to me an effective
rebuttal.
But they can't stop me from ranting here... bwa ha ha ha ha!!!!
OK.
Maybe somebody happening to read this rant could outline the ansatz of
a calculation to answer the following question -- just outline how to
approach it, and I will struggle with the details:
The setup:
I drop, from a given static position above the event horizon, an unlit
rocket into a canonical Schwarzschild black hole. I hold in my hand a
universal IR rocket remote, with a button labeled "return". I point
the remote towards the falling rocket, press the button, and a light
pulse overtakes the rocket, instructing it to light off its motors,
save itself from oblivion, and return it to my position. A finite time
later I again hold the rocket in my hand.
The question:
How long can I wait before hitting the button so that the light pulse
will reach the rocket before it crosses the horizon in its own proper
time, signaling it to return? [Ignore how much thrust will be
required, and how blueshifted the signal will be when it reaches the
rocket.]
The possibilities:
Either the time available to hit the remote is finite or infinite. If
finite, this would be circumstantial evidence supporting the claim that
"does too fall in before the end of time": what we can no longer
prevent may perhaps as well have happened, even if we can't know just
when. If infinite, on the other hand, this would support the assertion
that the crossing event never happens -- an irreversible event which
can always be prevented from happening presumably never "happens".
Please help crankdom everywhere by any hints on how to perform the
calculation!
I especially appeal to the large and vibrant crank population in the
unmoderated groups, since, performing a correct calculation may give a
viable chance to show the experts wrong, wrong, wrong, bwa ha, ha...
and etc. -- at least the ones who insist that things do fall in before
aeternity. Learn how to do a calculation in GR! Prove experts wrong!
Have fun!
Anybody want to place bets on which way the calculation will go?
(Crow pie already cooling in pantry, just in case).
.
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: What an odd way to hold a discussion... question follows |
25 Sep 2006 10:05:51 PM |
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Dear Edward Green:
"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1159238407.788715.89200@m73g2000cwd.googlegroups.com...
....
Either the time available to hit the remote is
finite or infinite.
Finite. Calculable, but not observable, since the image you
perceive outside lags *far* behind the actual object position.
Sort of like what teenagers let their parents see, when going out
on a date. When you see something you don't like, the deed is
likely already done.
If finite, this would be circumstantial evidence
supporting the claim that "does too fall in before
the end of time":
I think the argument is to see the last of its "image", not the
object itself. The image gets more and more redshifted, and
persists unitl the BH evaporates or additional mass/energy is
added.
what we can no longer prevent may perhaps as
well have happened, even if we can't know just
when.
"Know" or "calculate"?
Anybody want to place bets on which way the calculation will
go?
Pretty well covered. George Dishman told me how to do it in the
thread "CMBR and Neutron Star" on sci.astro. Calculate time from
"infinity" to your remote, then infinity to event horizon. The
difference is the time it would take before your ship went "over
the edge". Assuming of course that you stopped the remote's
infall...
http://groups.google.com/group/sci.astro/msg/dc8d9f40690dbff1
Initial velocity is quite a bit stiffer to handle...
(Crow pie already cooling in pantry, just in case).
I had game bird pie in a restaurant in Virginia once...
Farnsworth House perhaps. Tastes like chicken.
David A. Smith
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| User: "Edward Green" |
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| Title: Re: What an odd way to hold a discussion... question follows |
07 Oct 2006 03:35:37 PM |
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N:dlzc D:aol T:com (dlzc) wrote:
Dear Edward Green:
"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1159238407.788715.89200@m73g2000cwd.googlegroups.com...
...
Either the time available to hit the remote is
finite or infinite.
Finite. Calculable, but not observable, since the image you
perceive outside lags *far* behind the actual object position.
Sort of like what teenagers let their parents see, when going out
on a date. When you see something you don't like, the deed is
likely already done.
I disagree that it is not "observable" that the remote signal has
reached the rocket/probe before the event horizon. The rocket could
either turn around and come back, or send a return message. A variant
: simply look for a reflected radar signal.
OTOH, the result that the signal does not reach the rocket in time is
perhaps "unobservable", since we would simply wait for a return signal
which never arrived.
If finite, this would be circumstantial evidence
supporting the claim that "does too fall in before
the end of time":
I think the argument is to see the last of its "image", not the
object itself. The image gets more and more redshifted, and
persists unitl the BH evaporates or additional mass/energy is
added.
I made the question operational to avoid questions about "what we see".
If _something_ can return to us from the dropped probe in finite time
-- either the probe itself, or a signal -- then I suggest as an
operational definition that "the probe had not crossed the horizon at
the time we sent the inquiry signal".
what we can no longer prevent may perhaps as
well have happened, even if we can't know just
when.
"Know" or "calculate"?
We have problems with simultaneity with local and distant clocks, so
the question "when" the horizon was crossed by these same local clocks,
is at least ambiguous. But we could at least determine "not yet so
far" if a signal sent at time t received a reply.
Anybody want to place bets on which way the calculation will
go?
Pretty well covered. George Dishman told me how to do it in the
thread "CMBR and Neutron Star" on sci.astro. Calculate time from
"infinity" to your remote, then infinity to event horizon. The
difference is the time it would take before your ship went "over
the edge". Assuming of course that you stopped the remote's
infall...
I'm not sure what you are calculating, or if it is the same thing I
asked for: you assert, again, that the time available to send a light
pulse from your (fixed in Schwarzschild coordinate r) observer's
location to an infalling probe, to have it reach the probe before the
probe reaches the horizon, is finite?
Initial velocity is quite a bit stiffer to handle...
(Crow pie already cooling in pantry, just in case).
I had game bird pie in a restaurant in Virginia once...
Farnsworth House perhaps. Tastes like chicken.
Almost all unusual meat tastes like chicken. Except, presumably, crow.
I like crows and would not actually eat one.
Thanks for your reply.
.
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
26 Sep 2006 08:46:09 AM |
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Edward Green wrote:
I know complaining about the awful injustice of it all only makes me
more of a crank, but...
Essaying to write to sci.physics.research, I was successful in starting
in a thread, but unable to reply because I am asked for a "citation"
for a randomly chosen proper name, and honestly reply it was a randomly
chosen name, and why do you think I need a "citation", with the
injunction "keep it civil"(!). I was unable to offer a possibility not
considered by other respondents with a sketch of the simple calculation
(being merely an integral) because I have "not done a calculation"(!),
although part of my motive in writing was in fact to ask for hints how
to perform simple calculations in GR.
Of course I can't help but wonder if the individual of the same given
name as one of the moderators who sometimes posts in
sci.physics.relativity and sci.physics is in fact the same individual,
in which case telling him he had no bloody idea what he was talking
about in that latter, uncivil, group -- which he didn't -- of course
gives license for whatever petty revenge he is able to extract by
virtue of whatever other positions of dubious authority he may occupy.
Not mentioning names.
Then again maybe I shouldn't have mentioned that my motivation in
learning to do some simple calculations involving the metric was to
accumulate circumstantial evidence for my hunch that nothing, in fact,
ever falls into a black hole -- by preponderance of the semantical
evidence of what we might like to mean by "ever" -- despite the one
piece of circumstantial evidence commonly offered that "does too fall
in", for which I already humbly hold what seems to me an effective
rebuttal.
But they can't stop me from ranting here... bwa ha ha ha ha!!!!
OK.
Maybe somebody happening to read this rant could outline the ansatz of
a calculation to answer the following question -- just outline how to
approach it, and I will struggle with the details:
The setup:
I drop, from a given static position above the event horizon, an unlit
rocket into a canonical Schwarzschild black hole. I hold in my hand a
universal IR rocket remote, with a button labeled "return". I point
the remote towards the falling rocket, press the button, and a light
pulse overtakes the rocket, instructing it to light off its motors,
save itself from oblivion, and return it to my position. A finite time
later I again hold the rocket in my hand.
The question:
How long can I wait before hitting the button so that the light pulse
will reach the rocket before it crosses the horizon in its own proper
time, signaling it to return? [Ignore how much thrust will be
required, and how blueshifted the signal will be when it reaches the
rocket.]
Ignoring the limited lifetime stumbling block, you can wait forever -
you'll always be able to retrieve your rocket (provided it's capable of
unlimited thrust). What you haven't recognized, is that, in Relativity,
your forever doesn't correspond to everyone else's forever. From some
other perspective, the rocket will indeed become unretrievable (e.g.,
from the rocket's perspective).
The possibilities:
Either the time available to hit the remote is finite or infinite. If
finite, this would be circumstantial evidence supporting the claim that
"does too fall in before the end of time": what we can no longer
prevent may perhaps as well have happened, even if we can't know just
when. If infinite, on the other hand, this would support the assertion
that the crossing event never happens -- an irreversible event which
can always be prevented from happening presumably never "happens".
Please help crankdom everywhere by any hints on how to perform the
calculation!
I especially appeal to the large and vibrant crank population in the
unmoderated groups, since, performing a correct calculation may give a
viable chance to show the experts wrong, wrong, wrong, bwa ha, ha...
and etc. -- at least the ones who insist that things do fall in before
aeternity. Learn how to do a calculation in GR! Prove experts wrong!
Have fun!
Anybody want to place bets on which way the calculation will go?
(Crow pie already cooling in pantry, just in case).
.
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
27 Sep 2006 08:18:54 AM |
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jem wrote:
Edward Green wrote:
The setup:
I drop, from a given static position above the event horizon, an unlit
rocket into a canonical Schwarzschild black hole. I hold in my hand a
universal IR rocket remote, with a button labeled "return". I point
the remote towards the falling rocket, press the button, and a light
pulse overtakes the rocket, instructing it to light off its motors,
save itself from oblivion, and return it to my position. A finite time
later I again hold the rocket in my hand.
The question:
How long can I wait before hitting the button so that the light pulse
will reach the rocket before it crosses the horizon in its own proper
time, signaling it to return? [Ignore how much thrust will be
required, and how blueshifted the signal will be when it reaches the
rocket.]
Ignoring the limited lifetime stumbling block, you can wait forever -
you'll always be able to retrieve your rocket (provided it's capable of
unlimited thrust). What you haven't recognized, is that, in Relativity,
your forever doesn't correspond to everyone else's forever. From some
other perspective, the rocket will indeed become unretrievable (e.g.,
from the rocket's perspective).
That conclusion was based on reasoning that any light signal from the
remote to the rocket always has a coordinate speed that's greater than
the coordinate speed of light at the rocket's location, which in turn is
greater than the rocket's coordinate speed, which implies the closing
speed between signal and rocket must be positive which implies the
signal must reach the rocket (since the coordintate distance that both
travel is bounded by the horizon).
However, I'm having second thoughts about the correctness of all that.
If I can sort it out, I'll post an update.
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| User: "Tom Roberts" |
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| Title: Re: What an odd way to hold a discussion... question follows |
27 Sep 2006 08:53:55 PM |
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jem wrote:
jem wrote:
Ignoring the limited lifetime stumbling block, you can wait forever -
you'll always be able to retrieve your rocket (provided it's capable
of unlimited thrust).
No sensible rocket can have "unlimited thrust". As long as the rocket
has a finite maximum thrust, no matter how large, there will be a finite
time for you to retrieve it, and beyond then it will not be retrievable.
This is easy to see for the case of an accelerated observer in SR: once
the rocket falls behind the observer's Rindler horizon it is impossible
to retrieve it. This clearly happens in a finite time (measured by
either the observer or the rocket). Just like the case of a black hole
horizon, the accelerated observer will never actually observe the rocket
reach the horizon (requires infinite proper time of the observer);
nevertheless it will be impossible to retrieve it. And just like the
case of the black hole, the rocket easily observes itself falling behind
the observer's Rindler horizon.
Tom Roberts
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
28 Sep 2006 07:55:06 AM |
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Tom Roberts wrote:
jem wrote:
jem wrote:
Ignoring the limited lifetime stumbling block, you can wait forever -
you'll always be able to retrieve your rocket (provided it's capable
of unlimited thrust).
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
As long as the rocket
has a finite maximum thrust, no matter how large, there will be a finite
time for you to retrieve it, and beyond then it will not be retrievable.
This is easy to see for the case of an accelerated observer in SR: once
the rocket falls behind the observer's Rindler horizon it is impossible
to retrieve it. This clearly happens in a finite time (measured by
either the observer or the rocket).
Really? Please indicate what measurement the accelerating observer can
make to show that the rocket has crossed the horizon.
Just like the case of a black hole
horizon, the accelerated observer will never actually observe the rocket
reach the horizon (requires infinite proper time of the observer);
nevertheless it will be impossible to retrieve it. And just like the
case of the black hole, the rocket easily observes itself falling behind
the observer's Rindler horizon.
Tom Roberts
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| User: "Tom Roberts" |
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| Title: Re: What an odd way to hold a discussion... question follows |
28 Sep 2006 10:23:20 AM |
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jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities": the thrust of the rocket and
the time duration the observer can wait to retrieve the rocket. But you
have no way to "compare" these "infinities". Attempting to use
"infinities" in computations generally leads to nonsense....
IMHO a "rocket" that supposedly has unlimited thrust is not really a
rocket, but rather some other imaginary object. <shrug>
Tom Roberts
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
29 Sep 2006 07:39:09 AM |
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Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in the
context of this example simply means "can assume any finite value".
the thrust of the rocket and
the time duration the observer can wait to retrieve the rocket. But you
have no way to "compare" these "infinities". Attempting to use
"infinities" in computations generally leads to nonsense....
IMHO a "rocket" that supposedly has unlimited thrust is not really a
rocket, but rather some other imaginary object. <shrug>
What I'd like to know is why you're shrugging over the irrelevant issue
of what name gets assigned to the (ir)retrievable object, while
shrugging off the very relevant request that you support your claim that
accelerating observers are able to determine when objects cross their
horizons.
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| User: "Tom Roberts" |
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| Title: Re: What an odd way to hold a discussion... question follows |
29 Sep 2006 08:57:21 AM |
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jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in the
context of this example simply means "can assume any finite value".
If there is a finite upper bound on the thrust of the rocket, then there
is also a finite upper bound on how long the observer can wait to signal
it to return. So for any GIVEN rocket, with a GIVEN maximum thrust,
there will be a time limit on sending a retrieval signal.
As I say so often around here, you must be more precise in thought and
words. Your two statements are different: "it can have unlimited thrust"
is not quite the same as "can assume any finite value". But in any case
my previous paragraph is a better way to phrase this.
Tom Roberts
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
30 Sep 2006 07:33:55 AM |
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Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in the
context of this example simply means "can assume any finite value".
If there is a finite upper bound on the thrust of the rocket, then there
is also a finite upper bound on how long the observer can wait to signal
it to return. So for any GIVEN rocket, with a GIVEN maximum thrust,
there will be a time limit on sending a retrieval signal.
As I say so often around here, you must be more precise in thought and
words. Your two statements are different: "it can have unlimited thrust"
is not quite the same as "can assume any finite value". But in any case
my previous paragraph is a better way to phrase this.
There's no finite upper bound on either the rocket thrust or the signal
wait time - that's what's meant by "unlimited", and this use of the term
is completely standard. Although I now realize (thanks to Ben R-G) that
I was wrong in concluding that the rocket can always be retrieved, the
error has nothing to do with this terminological non-issue you've been
harping on.
And re. that other issue which keeps disappearing from these posts - you
know, one of the marks of a crackpot is an unwillingness to admit to
mistakes. You should consider that in regard to the "horizon crossing
measurement" claim you made and have been trying to sweep under the rug
ever since it was questioned.
.
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| User: "Edward Green" |
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| Title: Re: What an odd way to hold a discussion... question follows |
08 Oct 2006 08:45:37 AM |
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|
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in the
context of this example simply means "can assume any finite value".
If there is a finite upper bound on the thrust of the rocket, then there
is also a finite upper bound on how long the observer can wait to signal
it to return. So for any GIVEN rocket, with a GIVEN maximum thrust,
there will be a time limit on sending a retrieval signal.
As I say so often around here, you must be more precise in thought and
words. Your two statements are different: "it can have unlimited thrust"
is not quite the same as "can assume any finite value". But in any case
my previous paragraph is a better way to phrase this.
There's no finite upper bound on either the rocket thrust or the signal
wait time - that's what's meant by "unlimited", and this use of the term
is completely standard. Although I now realize (thanks to Ben R-G) that
I was wrong in concluding that the rocket can always be retrieved, the
error has nothing to do with this terminological non-issue you've been
harping on.
For what it's worth, I agree with you on the terminology and the
non-issue, and its (ir)relevance.
I've thought in the past we should use the phrase "finite unbounded" to
distinguish the case where a quantity may have any finite value, not
having a preset bound (like American Express) -- but not "infinity".
Maybe that's just the same thing as "unbounded" with redundant
emphasis. I would tend to accept "unlimited" as meaning the same
thing, but that's a question for the usage panel.
I like the fact that you are able to freely admit you were wrong about
something, and make a correction. I want to say that's a mark of
"sanity", but there's always the possibility that people who can't do
this are merely neurotic -- well, that's just a little insanity.
I accept for example that my hypothesis was probably wrong that we
could wait an indefinite amount of time before sending in a "return"
signal to catch a falling probe. I accept this even though I have yet
to demonstrate this to myself, but because a number of people whom I
trust to be able to perform such calculations say they have performed
it, that they agree on the answer, and that it is a standard answer.
Such things have a high probability of being "correct". If it were a
slightly more philosophically tinged issue, rather than a well-posed
mathematical question, I might more likely stand my ground.
.
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| User: "Ahmed Ouahi, Architect" |
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| Title: Re: What an odd way to hold a discussion... question follows |
08 Oct 2006 09:01:38 AM |
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The human intellect does understand some propositions perfectly, and thus in
these it has as much absolute certainty as Nature itself has.
Of such are the mathematical sciences alone, that is, geometry and
arithmetic, in which the Divine intellect indeed knows infinitely more
propositions, since it knows them all.
But with regard to those few which the human intellect does understand, I
believe that its knowledge equals the Divine in objective certainty.
-- Galileo
--
Ahmed Ouahi, Architect
Best Regards!
"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1160315137.176599.183110@h48g2000cwc.googlegroups.com...
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in the
context of this example simply means "can assume any finite value".
If there is a finite upper bound on the thrust of the rocket, then
there
is also a finite upper bound on how long the observer can wait to
signal
it to return. So for any GIVEN rocket, with a GIVEN maximum thrust,
there will be a time limit on sending a retrieval signal.
As I say so often around here, you must be more precise in thought and
words. Your two statements are different: "it can have unlimited
thrust"
is not quite the same as "can assume any finite value". But in any
case
my previous paragraph is a better way to phrase this.
There's no finite upper bound on either the rocket thrust or the signal
wait time - that's what's meant by "unlimited", and this use of the term
is completely standard. Although I now realize (thanks to Ben R-G) that
I was wrong in concluding that the rocket can always be retrieved, the
error has nothing to do with this terminological non-issue you've been
harping on.
For what it's worth, I agree with you on the terminology and the
non-issue, and its (ir)relevance.
I've thought in the past we should use the phrase "finite unbounded" to
distinguish the case where a quantity may have any finite value, not
having a preset bound (like American Express) -- but not "infinity".
Maybe that's just the same thing as "unbounded" with redundant
emphasis. I would tend to accept "unlimited" as meaning the same
thing, but that's a question for the usage panel.
I like the fact that you are able to freely admit you were wrong about
something, and make a correction. I want to say that's a mark of
"sanity", but there's always the possibility that people who can't do
this are merely neurotic -- well, that's just a little insanity.
I accept for example that my hypothesis was probably wrong that we
could wait an indefinite amount of time before sending in a "return"
signal to catch a falling probe. I accept this even though I have yet
to demonstrate this to myself, but because a number of people whom I
trust to be able to perform such calculations say they have performed
it, that they agree on the answer, and that it is a standard answer.
Such things have a high probability of being "correct". If it were a
slightly more philosophically tinged issue, rather than a well-posed
mathematical question, I might more likely stand my ground.
.
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| User: "Phil" |
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| Title: Re: What an odd way to hold a discussion... question follows |
02 Oct 2006 12:31:55 AM |
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jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in the
context of this example simply means "can assume any finite value".
If there is a finite upper bound on the thrust of the rocket, then
there is also a finite upper bound on how long the observer can wait
to signal it to return. So for any GIVEN rocket, with a GIVEN maximum
thrust, there will be a time limit on sending a retrieval signal.
As I say so often around here, you must be more precise in thought and
words. Your two statements are different: "it can have unlimited
thrust" is not quite the same as "can assume any finite value". But in
any case
my previous paragraph is a better way to phrase this.
There's no finite upper bound on either the rocket thrust or the signal
wait time - that's what's meant by "unlimited", and this use of the term
is completely standard. Although I now realize (thanks to Ben R-G) that
I was wrong in concluding that the rocket can always be retrieved, the
error has nothing to do with this terminological non-issue you've been
harping on.
And re. that other issue which keeps disappearing from these posts - you
know, one of the marks of a crackpot is an unwillingness to admit to
mistakes. You should consider that in regard to the "horizon crossing
measurement" claim you made and have been trying to sweep under the rug
ever since it was questioned.
I've noticed that about Tom. He ALWAYS deleted any comments on my
"universe circumnavigation" experiment after his initial response fell
flat. Isn't it a basic characteristic of science that we should actually
look for possible flaws in our current understanding of reality, with an
open mind? When did it become possible to inflate our egos by mindlessly
and illogically defending the current "Great Beliefs," as handed down to
us by the "Holy Experts?" When did practicing true SCIENCE become
unimportant, and how could anyone take pride in constantly practicing a
series of behaviors -- basically manipulative debating tricks -- that
people like Einstein and Newton HATED? I can only assume that such
idiots were rewarded for such unscientific behavior somewhere in life,
and are now incapable of practicing honest, genuinely scientific
behavior. You may or may not think I or my ideas are idiotic, Jem, but I
would guess that you would have good reasons, not ridiculous reasons,
for doing so. Of course, I have been wrong before ... ;-)
Annoyed Phil
.
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
02 Oct 2006 07:53:50 AM |
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|
Phil wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in the
context of this example simply means "can assume any finite value".
If there is a finite upper bound on the thrust of the rocket, then
there is also a finite upper bound on how long the observer can wait
to signal it to return. So for any GIVEN rocket, with a GIVEN maximum
thrust, there will be a time limit on sending a retrieval signal.
As I say so often around here, you must be more precise in thought
and words. Your two statements are different: "it can have unlimited
thrust" is not quite the same as "can assume any finite value". But
in any case
my previous paragraph is a better way to phrase this.
There's no finite upper bound on either the rocket thrust or the
signal wait time - that's what's meant by "unlimited", and this use of
the term is completely standard. Although I now realize (thanks to
Ben R-G) that I was wrong in concluding that the rocket can always be
retrieved, the error has nothing to do with this terminological
non-issue you've been harping on.
And re. that other issue which keeps disappearing from these posts -
you know, one of the marks of a crackpot is an unwillingness to admit
to mistakes. You should consider that in regard to the "horizon
crossing measurement" claim you made and have been trying to sweep
under the rug ever since it was questioned.
I've noticed that about Tom. He ALWAYS deleted any comments on my
"universe circumnavigation" experiment after his initial response fell
flat. Isn't it a basic characteristic of science that we should actually
look for possible flaws in our current understanding of reality, with an
open mind? When did it become possible to inflate our egos by mindlessly
and illogically defending the current "Great Beliefs," as handed down to
us by the "Holy Experts?" When did practicing true SCIENCE become
unimportant, and how could anyone take pride in constantly practicing a
series of behaviors -- basically manipulative debating tricks -- that
people like Einstein and Newton HATED? I can only assume that such
idiots were rewarded for such unscientific behavior somewhere in life,
and are now incapable of practicing honest, genuinely scientific
behavior. You may or may not think I or my ideas are idiotic, Jem, but I
would guess that you would have good reasons, not ridiculous reasons,
for doing so. Of course, I have been wrong before ... ;-)
Annoyed Phil
It doesn't appear that your issue and mine are the same, Phil. I don't
see anything wrong in simply choosing not to discuss a particular issue,
but when somebody makes a claim that's subsequently called into
question, it's inappropriate for them to just walk away from it without
a word.
.
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| User: "Phil" |
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| Title: Re: What an odd way to hold a discussion... question follows |
02 Oct 2006 03:49:31 PM |
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|
jem wrote:
Phil wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in
the context of this example simply means "can assume any finite
value".
If there is a finite upper bound on the thrust of the rocket, then
there is also a finite upper bound on how long the observer can wait
to signal it to return. So for any GIVEN rocket, with a GIVEN
maximum thrust, there will be a time limit on sending a retrieval
signal.
As I say so often around here, you must be more precise in thought
and words. Your two statements are different: "it can have unlimited
thrust" is not quite the same as "can assume any finite value". But
in any case
my previous paragraph is a better way to phrase this.
There's no finite upper bound on either the rocket thrust or the
signal wait time - that's what's meant by "unlimited", and this use
of the term is completely standard. Although I now realize (thanks
to Ben R-G) that I was wrong in concluding that the rocket can always
be retrieved, the error has nothing to do with this terminological
non-issue you've been harping on.
And re. that other issue which keeps disappearing from these posts -
you know, one of the marks of a crackpot is an unwillingness to admit
to mistakes. You should consider that in regard to the "horizon
crossing measurement" claim you made and have been trying to sweep
under the rug ever since it was questioned.
I've noticed that about Tom. He ALWAYS deleted any comments on my
"universe circumnavigation" experiment after his initial response fell
flat. Isn't it a basic characteristic of science that we should
actually look for possible flaws in our current understanding of
reality, with an open mind? When did it become possible to inflate our
egos by mindlessly and illogically defending the current "Great
Beliefs," as handed down to us by the "Holy Experts?" When did
practicing true SCIENCE become unimportant, and how could anyone take
pride in constantly practicing a series of behaviors -- basically
manipulative debating tricks -- that people like Einstein and Newton
HATED? I can only assume that such idiots were rewarded for such
unscientific behavior somewhere in life, and are now incapable of
practicing honest, genuinely scientific behavior. You may or may not
think I or my ideas are idiotic, Jem, but I would guess that you would
have good reasons, not ridiculous reasons, for doing so. Of course, I
have been wrong before ... ;-)
Annoyed Phil
It doesn't appear that your issue and mine are the same, Phil. I don't
see anything wrong in simply choosing not to discuss a particular issue,
but when somebody makes a claim that's subsequently called into
question, it's inappropriate for them to just walk away from it without
a word.
What you have just described is scientifically dishonest, as it prevents
any possibility of correcting errors, whether those errors are our own,
or part of the current scientific beliefs. That is what I object to.
When I posted my analysis, Tom gave an initial response, and when my
response showed that his response was nonsense, he avoided the core of
my response, and tried to find some alternate method of attacking my
ideas. That is something that we should do in a normal debate, even
though it is intellectually dishonest, but should not do in *scientific*
"debates." I think we have exactly the same issue.
Stubborn (and possibly incorrect) Phil
.
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
03 Oct 2006 07:25:28 AM |
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|
Phil wrote:
jem wrote:
Phil wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in
the context of this example simply means "can assume any finite
value".
If there is a finite upper bound on the thrust of the rocket, then
there is also a finite upper bound on how long the observer can
wait to signal it to return. So for any GIVEN rocket, with a GIVEN
maximum thrust, there will be a time limit on sending a retrieval
signal.
As I say so often around here, you must be more precise in thought
and words. Your two statements are different: "it can have
unlimited thrust" is not quite the same as "can assume any finite
value". But in any case
my previous paragraph is a better way to phrase this.
There's no finite upper bound on either the rocket thrust or the
signal wait time - that's what's meant by "unlimited", and this use
of the term is completely standard. Although I now realize (thanks
to Ben R-G) that I was wrong in concluding that the rocket can
always be retrieved, the error has nothing to do with this
terminological non-issue you've been harping on.
And re. that other issue which keeps disappearing from these posts -
you know, one of the marks of a crackpot is an unwillingness to
admit to mistakes. You should consider that in regard to the
"horizon crossing measurement" claim you made and have been trying
to sweep under the rug ever since it was questioned.
I've noticed that about Tom. He ALWAYS deleted any comments on my
"universe circumnavigation" experiment after his initial response
fell flat. Isn't it a basic characteristic of science that we should
actually look for possible flaws in our current understanding of
reality, with an open mind? When did it become possible to inflate
our egos by mindlessly and illogically defending the current "Great
Beliefs," as handed down to us by the "Holy Experts?" When did
practicing true SCIENCE become unimportant, and how could anyone take
pride in constantly practicing a series of behaviors -- basically
manipulative debating tricks -- that people like Einstein and Newton
HATED? I can only assume that such idiots were rewarded for such
unscientific behavior somewhere in life, and are now incapable of
practicing honest, genuinely scientific behavior. You may or may not
think I or my ideas are idiotic, Jem, but I would guess that you
would have good reasons, not ridiculous reasons, for doing so. Of
course, I have been wrong before ... ;-)
Annoyed Phil
It doesn't appear that your issue and mine are the same, Phil. I
don't see anything wrong in simply choosing not to discuss a
particular issue, but when somebody makes a claim that's subsequently
called into question, it's inappropriate for them to just walk away
from it without a word.
What you have just described is scientifically dishonest, as it prevents
any possibility of correcting errors, whether those errors are our own,
or part of the current scientific beliefs. That is what I object to.
When I posted my analysis, Tom gave an initial response, and when my
response showed that his response was nonsense, he avoided the core of
my response, and tried to find some alternate method of attacking my
ideas. That is something that we should do in a normal debate, even
though it is intellectually dishonest, but should not do in *scientific*
"debates." I think we have exactly the same issue.
I don't think so - my issue involves only bad manners - certainly
nothing that would warrant the label "dishonest".
Stubborn (and possibly incorrect) Phil
.
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| User: "Phil" |
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| Title: Re: What an odd way to hold a discussion... question follows |
08 Oct 2006 03:52:24 AM |
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jem wrote:
Phil wrote:
jem wrote:
Phil wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
jem wrote:
Tom Roberts wrote:
No sensible rocket can have "unlimited thrust".
It's a theoretical rocket - it can have unlimited thrust.
Then you have two different "infinities":
Not at all - there are *no* infinities involved. "Unlimited" in
the context of this example simply means "can assume any finite
value".
If there is a finite upper bound on the thrust of the rocket, then
there is also a finite upper bound on how long the observer can
wait to signal it to return. So for any GIVEN rocket, with a GIVEN
maximum thrust, there will be a time limit on sending a retrieval
signal.
As I say so often around here, you must be more precise in thought
and words. Your two statements are different: "it can have
unlimited thrust" is not quite the same as "can assume any finite
value". But in any case
my previous paragraph is a better way to phrase this.
There's no finite upper bound on either the rocket thrust or the
signal wait time - that's what's meant by "unlimited", and this use
of the term is completely standard. Although I now realize (thanks
to Ben R-G) that I was wrong in concluding that the rocket can
always be retrieved, the error has nothing to do with this
terminological non-issue you've been harping on.
And re. that other issue which keeps disappearing from these posts
- you know, one of the marks of a crackpot is an unwillingness to
admit to mistakes. You should consider that in regard to the
"horizon crossing measurement" claim you made and have been trying
to sweep under the rug ever since it was questioned.
I've noticed that about Tom. He ALWAYS deleted any comments on my
"universe circumnavigation" experiment after his initial response
fell flat. Isn't it a basic characteristic of science that we should
actually look for possible flaws in our current understanding of
reality, with an open mind? When did it become possible to inflate
our egos by mindlessly and illogically defending the current "Great
Beliefs," as handed down to us by the "Holy Experts?" When did
practicing true SCIENCE become unimportant, and how could anyone
take pride in constantly practicing a series of behaviors --
basically manipulative debating tricks -- that people like Einstein
and Newton HATED? I can only assume that such idiots were rewarded
for such unscientific behavior somewhere in life, and are now
incapable of practicing honest, genuinely scientific behavior. You
may or may not think I or my ideas are idiotic, Jem, but I would
guess that you would have good reasons, not ridiculous reasons, for
doing so. Of course, I have been wrong before ... ;-)
Annoyed Phil
It doesn't appear that your issue and mine are the same, Phil. I
don't see anything wrong in simply choosing not to discuss a
particular issue, but when somebody makes a claim that's subsequently
called into question, it's inappropriate for them to just walk away
from it without a word.
What you have just described is scientifically dishonest, as it
prevents any possibility of correcting errors, whether those errors
are our own, or part of the current scientific beliefs. That is what I
object to. When I posted my analysis, Tom gave an initial response,
and when my response showed that his response was nonsense, he avoided
the core of my response, and tried to find some alternate method of
attacking my ideas. That is something that we should do in a normal
debate, even though it is intellectually dishonest, but should not do
in *scientific* "debates." I think we have exactly the same issue.
I don't think so - my issue involves only bad manners - certainly
nothing that would warrant the label "dishonest".
Oh ... okay. Well in that case, never mind!
Phil
Stubborn (and possibly incorrect) Phil
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| User: "Tom Roberts" |
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| Title: Re: What an odd way to hold a discussion... question follows |
27 Sep 2006 11:58:53 PM |
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Tom Roberts wrote:
jem wrote:
jem wrote:
Ignoring the limited lifetime stumbling block, you can wait forever -
you'll always be able to retrieve your rocket (provided it's capable
of unlimited thrust).
No sensible rocket can have "unlimited thrust". As long as the rocket
has a finite maximum thrust, no matter how large, there will be a finite
time for you to retrieve it, and beyond then it will not be retrievable.
This is easy to see for the case of an accelerated observer in SR: once
the rocket falls behind the observer's Rindler horizon it is impossible
to retrieve it. This clearly happens in a finite time (measured by
either the observer or the rocket). Just like the case of a black hole
horizon, the accelerated observer will never actually observe the rocket
reach the horizon (requires infinite proper time of the observer);
nevertheless it will be impossible to retrieve it. And just like the
case of the black hole, the rocket easily observes itself falling behind
the observer's Rindler horizon.
I forgot to point out that in this accelerated-observer case in SR, it
is clear that even if the rocket has unlimited thrust, once it falls
behind the observer's Rindler horizon it cannot possibly catch up to
him. Similarly for the black hole, once the rocket falls inside the
horizon, it cannot possibly escape, even if it has unlimited thrust.
Tom Roberts
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
28 Sep 2006 08:00:41 AM |
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Tom Roberts wrote:
Tom Roberts wrote:
jem wrote:
jem wrote:
Ignoring the limited lifetime stumbling block, you can wait forever
- you'll always be able to retrieve your rocket (provided it's
capable of unlimited thrust).
No sensible rocket can have "unlimited thrust". As long as the rocket
has a finite maximum thrust, no matter how large, there will be a
finite time for you to retrieve it, and beyond then it will not be
retrievable.
This is easy to see for the case of an accelerated observer in SR:
once the rocket falls behind the observer's Rindler horizon it is
impossible to retrieve it. This clearly happens in a finite time
(measured by either the observer or the rocket). Just like the case of
a black hole horizon, the accelerated observer will never actually
observe the rocket reach the horizon (requires infinite proper time of
the observer); nevertheless it will be impossible to retrieve it. And
just like the case of the black hole, the rocket easily observes
itself falling behind the observer's Rindler horizon.
I forgot to point out that in this accelerated-observer case in SR, it
is clear that even if the rocket has unlimited thrust, once it falls
behind the observer's Rindler horizon it cannot possibly catch up to
him.
Clearly, the accelerated observer won't be able to retrieve the rocket
"after" it has crossed the horizon, since, for thar observer, time will
have literally run out prior to the crossing.
Similarly for the black hole, once the rocket falls inside the
horizon, it cannot possibly escape, even if it has unlimited thrust.
Yes, but whether or not it could, was never in question.
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| User: "Edward Green" |
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| Title: Re: What an odd way to hold a discussion... question follows |
07 Oct 2006 07:53:50 PM |
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jem wrote:
Edward Green wrote:
How long can I wait before hitting the button so that the light pulse
will reach the rocket before it crosses the horizon in its own proper
time, signaling it to return? [Ignore how much thrust will be
required, and how blueshifted the signal will be when it reaches the
rocket.]
Ignoring the limited lifetime stumbling block, you can wait forever -
you'll always be able to retrieve your rocket (provided it's capable of
unlimited thrust).
It has already been mentioned by authoritative posters (no irony
involved, since I can't reproduce their calculations, but have little
reason to doubt them) that this is incorrect. I have nothing to add.
What you haven't recognized, is that, in Relativity,
your forever doesn't correspond to everyone else's forever.
But I have something to add here (besides more of the fifth of scotch I
just purchased to my glass). Let's start at the beginning...
In SR, given not terribly unfriendly accelerations, all observers are
equivalent in a strong sense: at close of business, tired out from a
long day of playing with clocks and meter sticks, they may all turn
their rockets around and head for the station, where they can swap
stories over a few drinks at the bar.
But in some spacetimes of GR, or in the event of sufficiently
unfriendly accelerations in SR, all observers lose equivalency, in the
sense that for a given observer, there are some others with whom he can
eventually no longer communicate. They may as well be "out of his
universe". We may still like to hold them morally equivalent to us, in
a sense of fair play, but we might also claim with some justice that
what can never be communicated to us is no longer part of our world.
Here's a related scenario:
On the table before me I have a Jack-in-the-Box. I have a physical
theory of this Box, and it tells me that Jack will spring out when my
clock reads "t = infinity". Hmm... I say. Does Jack ever spring out?
I'd say not... saying he springs out "at infinity" is just a funny way
of saying "never".
But now Tom comes in the room, and accuses me of being a coordinate
chauvinist. For, he, claims, closer examination of my theory reveals
that local physical law is invariant in form under a transformation
which places me inside the box and maps my "infinity" to a finite time.
Jack pops out in finite time by _his_ watch, so only my prejudice leads
me to claim he "never" pops out. I am a coordinate-centric pig.
Should this argument sway me?
It's partially a question of semantics, but I'd still argue that in my
universe, this transformation doesn't amount to a hill of beans. I and
all my descendants can watch the box until the stars wink out, and it
won't pop. What they will see is that "time" inside the box is running
down, and in fact running asymptotically to a finite duration. Not
only is the box never going to pop, its internal clock is never going
to pass midnight. This existence of the cute transformation symmetry
doesn't change anything operational for me.
It is, or was, my supposition that black holes (the objects described
by the theory of GR) in some respects act like this box, but with a
twist. There is the added complication that not only will we never see
the box pop, but it is moved a far away from us, so that our mapping of
"simultaneous" inside and outside times becomes ambiguous! Damn
nuisance. This makes it harder to dismiss the aforementioned
transformation as a mathematical existent but operationally
inconsequent oddity. If we _could_ always get a signal to the box
before it popped (contact the infalling probe), ordering it to put on
the latch, then we would have support for the idea that it still never
popped, though we hid it far away. But we can't always get the signal
to it in time.
Now, like a persistent defense lawyer, I see this result as a setback,
but do not admit defeat. There is something funny going on here. Can
the following mapping be made mathematically precise?
Suppose an object is receding from us in flat spacetime, undergoing
constant acceleration -- asymptotically approaching c, of course, in a
fixed Lorentzian frame. Suppose we sent a light pulse after it,
initially lagging it by a distance d (in the same frame). The closure
rate in this fixed frame is given by c - v_m, where v_m -> c. The
closure rate goes to zero, and the net distance closed (I emphasize,
measured in the fixed frame) is given by the integral of the closure
rate from initiation of the pulse to t = oo. The acceleration profile
may be chosen so that net_distance_closed < d : the light never catches
the particle.
I suspect that if we integrated the proper time of the particle under
such an acceleration profile we would find that total elapsed proper
time following the passing of any fixed coordinate point is finite: the
particle runs down, and only takes finite proper time to get to
infinity!
Supposing an acceleration profile can be produced with this property,
we seem to have a close analogy of an infalling particle in a black
hole: after some finite delay, light can no longer catch it, and it
takes finite proper time to reach an "event" we would tend to label
with "t = infinity".
Does that mean the particle really "crosses infinity"?
Project for a rainy day: devise such an explicit acceleration profile,
and examine its behavior in the proper time of the particle
extrapolated past the finite proper time corresponding to "t =
infinity". Is there a second anomaly at a later, finite, proper time,
suggestive of a "spacetime singularity"?
.
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| User: "jem" |
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| Title: Re: What an odd way to hold a discussion... question follows |
08 Oct 2006 08:17:12 AM |
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Edward Green wrote:
jem wrote:
Edward Green wrote:
How long can I wait before hitting the button so that the light pulse
will reach the rocket before it crosses the horizon in its own proper
time, signaling it to return? [Ignore how much thrust will be
required, and how blueshifted the signal will be when it reaches the
rocket.]
Ignoring the limited lifetime stumbling block, you can wait forever -
you'll always be able to retrieve your rocket (provided it's capable of
unlimited thrust).
It has already been mentioned by authoritative posters (no irony
involved, since I can't reproduce their calculations, but have little
reason to doubt them) that this is incorrect. I have nothing to add.
What you haven't recognized, is that, in Relativity,
your forever doesn't correspond to everyone else's forever.
But I have something to add here (besides more of the fifth of scotch I
just purchased to my glass). Let's start at the beginning...
In SR, given not terribly unfriendly accelerations, all observers are
equivalent in a strong sense: at close of business, tired out from a
long day of playing with clocks and meter sticks, they may all turn
their rockets around and head for the station, where they can swap
stories over a few drinks at the bar.
But in some spacetimes of GR, or in the event of sufficiently
unfriendly accelerations in SR, all observers lose equivalency, in the
sense that for a given observer, there are some others with whom he can
eventually no longer communicate. They may as well be "out of his
universe". We may still like to hold them morally equivalent to us, in
a sense of fair play, but we might also claim with some justice that
what can never be communicated to us is no longer part of our world.
Here's a related scenario:
On the table before me I have a Jack-in-the-Box. I have a physical
theory of this Box, and it tells me that Jack will spring out when my
clock reads "t = infinity". Hmm... I say. Does Jack ever spring out?
I'd say not... saying he springs out "at infinity" is just a funny way
of saying "never".
"Never", as measured by your clock.
But now Tom comes in the room, and accuses me of being a coordinate
chauvinist. For, he, claims, closer examination of my theory reveals
that local physical law is invariant in form under a transformation
which places me inside the box and maps my "infinity" to a finite time.
Jack pops out in finite time by _his_ watch, so only my prejudice leads
me to claim he "never" pops out. I am a coordinate-centric pig.
Should this argument sway me?
The argument that it'll pop out in a finite time if you'll just keep
time with a different clock? I don't think so.
It's partially a question of semantics, but I'd still argue that in my
universe, this transformation doesn't amount to a hill of beans. I and
all my descendants can watch the box until the stars wink out, and it
won't pop. What they will see is that "time" inside the box is running
down, and in fact running asymptotically to a finite duration. Not
only is the box never going to pop, its internal clock is never going
to pass midnight. This existence of the cute transformation symmetry
doesn't change anything operational for me.
That is, unless you're capable of adopting different "time perspectives"
(e.g. by moving differently).
It is, or was, my supposition that black holes (the objects described
by the theory of GR) in some respects act like this box, but with a
twist. There is the added complication that not only will we never see
the box pop, but it is moved a far away from us, so that our mapping of
"simultaneous" inside and outside times becomes ambiguous! Damn
nuisance. This makes it harder to dismiss the aforementioned
transformation as a mathematical existent but operationally
inconsequent oddity. If we _could_ always get a signal to the box
before it popped (contact the infalling probe), ordering it to put on
the latch, then we would have support for the idea that it still never
popped, though we hid it far away. But we can't always get the signal
to it in time.
Now, like a persistent defense lawyer, I see this result as a setback,
but do not admit defeat. There is something funny going on here. Can
the following mapping be made mathematically precise?
Suppose an object is receding from us in flat spacetime, undergoing
constant acceleration -- asymptotically approaching c, of course, in a
fixed Lorentzian frame. Suppose we sent a light pulse after it,
initially lagging it by a distance d (in the same frame). The closure
rate in this fixed frame is given by c - v_m, where v_m -> c. The
closure rate goes to zero, and the net distance closed (I emphasize,
measured in the fixed frame) is given by the integral of the closure
rate from initiation of the pulse to t = oo. The acceleration profile
may be chosen so that net_distance_closed < d : the light never catches
the particle.
Yes.
I suspect that if we integrated the proper time of the particle under
such an acceleration profile we would find that total elapsed proper
time following the passing of any fixed coordinate point is finite: the
particle runs down, and only takes finite proper time to get to
infinity!
No.
Supposing an acceleration profile can be produced with this property,
we seem to have a close analogy of an infalling particle in a black
hole: after some finite delay, light can no longer catch it, and it
takes finite proper time to reach an "event" we would tend to label
with "t = infinity".
No, the coordinate clocks encountered by the accelerating object will
always read a finite time.
Does that mean the particle really "crosses infinity"?
Project for a rainy day: devise such an explicit acceleration profile,
and examine its behavior in the proper time of the particle
extrapolated past the finite proper time corresponding to "t =
infinity". Is there a second anomaly at a later, finite, proper time,
suggestive of a "spacetime singularity"?
You won't find your "singularity" by looking in the direction of
acceleration, however if you look in the opposite direction, you'll see
a region (the so-called Rindler Horizon), which, in some respects,
behaves like a BH horizon. In particular, any object that crosses this
horizon does so at the accelerator's "t = infinity".
.
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| User: "Edward Green" |
|
| Title: Re: What an odd way to hold a discussion... question follows |
09 Oct 2006 06:50:11 PM |
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|
jem patiently waded through my screed, and wrote:
Edward Green wrote:
jem wrote:
Edward Green wrote:
On the table before me I have a Jack-in-the-Box. I have a physical
theory of this Box, and it tells me that Jack will spring out when my
clock reads "t = infinity". Hmm... I say. Does Jack ever spring out?
I'd say not... saying he springs out "at infinity" is just a funny way
of saying "never".
"Never", as measured by your clock.
Agreed.
But now Tom comes in the room, and accuses me of being a coordinate
chauvinist. For, he, claims, closer examination of my theory reveals
that local physical law is invariant in form under a transformation
which places me inside the box and maps my "infinity" to a finite time.
Jack pops out in finite time by _his_ watch, so only my prejudice leads
me to claim he "never" pops out. I am a coordinate-centric pig.
Should this argument sway me?
The argument that it'll pop out in a finite time if you'll just keep
time with a different clock? I don't think so.
Good. I don't think too much of it either.
It's partially a question of semantics, but I'd still argue that in my
universe, this transformation doesn't amount to a hill of beans. I and
all my descendants can watch the box until the stars wink out, and it
won't pop. What they will see is that "time" inside the box is running
down, and in fact running asymptotically to a finite duration. Not
only is the box never going to pop, its internal clock is never going
to pass midnight. This existence of the cute transformation symmetry
doesn't change anything operational for me.
That is, unless you're capable of adopting different "time perspectives"
(e.g. by moving differently).
So far I haven't said anything about movement. I'm abstracting this
"different observers" business to a case where the observer who seems
to slow down and stop is right there in front of us, so we don't have
any weasel room about simultaneity and distant regions of spacetime.
Suppose an object is receding from us in flat spacetime, undergoing
constant acceleration -- asymptotically approaching c, of course, in a
fixed Lorentzian frame. Suppose we sent a light pulse after it,
initially lagging it by a distance d (in the same frame). The closure
rate in this fixed frame is given by c - v_m, where v_m -> c. The
closure rate goes to zero, and the net distance closed (I emphasi | | | | |
