On Fri, 26 Aug 2005 12:05:53 +0200, Kim B wrote:

On Tue, 23 Aug 2005 02:06:41 GMT, wrote:

Well, with the velocity being only 3 meters / second, and the
acceleration being only 1 g, I can experience how objects change (on a
local level) when they move from one reference frame to another. For
example, some posters in this group believe if the rod is made long
enough, a person holding one end of the rod will be accelerated to a
velocity approaching the speed of light. But with parameters like 3
meters / second and a 1 g acceleration it is easy for me to see that
that notion is incorrect.

It is of no use using "everyday" accelerations when you use very long
stick. You cannot use "easy for me to see" in these cases.

If you accelerate a rigid rod of 1 ly by pulling the front with
approx. 9.5 m/s/s (a little less than normal gravity), the
acceleration of a point at the rod as seen in the rest system will
approach infinity as the point's position approches 1 ly from the
front end (and this is of course the point, where the rod will break,
no matter how strong it is)

Kim
Let's look at things with respect to the problem I posted, please post
your answer to the following questions.
1. If I place all points along the length of a steel rod 1 meter in
diameter and 10 meters in length onto a conveyer belt moving 3 meters
/ second, will the rod break?
2. If the rod is 100 meters in length when I do this, will it break?
3. If the rod is 1000 meters in length when I do this, will it break?
4. If the rod breaks, what length does it have to be before it
breaks, and at what point of the rod will the break occur?
5. If the rod is only 1 cm in diameter, does it break at a different
point or at a different length?
Thanks,
David

On Sat, 27 Aug 2005 03:09:20 GMT, wrote:

On Fri, 26 Aug 2005 12:05:53 +0200, Kim B wrote:

If you accelerate a rigid rod of 1 ly by pulling the front with
approx. 9.5 m/s/s (a little less than normal gravity), the
acceleration of a point at the rod as seen in the rest system will
approach infinity as the point's position approches 1 ly from the
front end (and this is of course the point, where the rod will break,
no matter how strong it is)

Kim
Let's look at things with respect to the problem I posted, please post
your answer to the following questions.
1. If I place all points along the length of a steel rod 1 meter in
diameter and 10 meters in length onto a conveyer belt moving 3 meters
/ second, will the rod break?
2. If the rod is 100 meters in length when I do this, will it break?
3. If the rod is 1000 meters in length when I do this, will it break?
4. If the rod breaks, what length does it have to be before it
breaks, and at what point of the rod will the break occur?
5. If the rod is only 1 cm in diameter, does it break at a different
point or at a different length?
Thanks,
David


Forget about the belt. Read the link I sent you a while a go, learn to
understand spacetime diagrams, use them to understand what happens
when a RIGID rod is accelerated, and why an event horison occurs
approx. 1 ly down the rod when the front end is accelerated 9.5 m/s/s.
Thats the way of learning, it takes a few hours (I learned a lot this
way).

Kim

On Sat, 27 Aug 2005 03:09:20 GMT, wrote:

Let's look at things with respect to the problem I posted, please post
your answer to the following questions.
1. If I place all points along the length of a steel rod 1 meter in
diameter and 10 meters in length onto a conveyer belt moving 3 meters
/ second, will the rod break?
2. If the rod is 100 meters in length when I do this, will it break?
3. If the rod is 1000 meters in length when I do this, will it break?
4. If the rod breaks, what length does it have to be before it
breaks, and at what point of the rod will the break occur?
5. If the rod is only 1 cm in diameter, does it break at a different
point or at a different length?
Thanks,
David


David, you are creating unnecessary complicated experiments, with the
most frequent flaw being an instantaneous speed change. It is of no
use that the speed change is small (in the "normal" range), as this
just make the error small. A small error can NOT be ignored when the
the length is huge. Huge length/small speed, small length/huge speed,
the problems don't go away.

My advice to you is to understand the simple problems first, e.g. the
acceleration problem. You obviously haven't got to that point yet.
Acceleration is certainly not intuitive and has a few surprises
builtin, e.g. an event horizon and varying clock and acceleration
rates along the rod.

I'm thus not going to comment further on your complex problems, partly
due to your "reputation" among some of the "older" posters in the
group.

Kim

On Sat, 27 Aug 2005 11:19:56 +0200, Kim B wrote:

On Sat, 27 Aug 2005 03:09:20 GMT, wrote:

Let's look at things with respect to the problem I posted, please post
your answer to the following questions.
1. If I place all points along the length of a steel rod 1 meter in
diameter and 10 meters in length onto a conveyer belt moving 3 meters
/ second, will the rod break?
2. If the rod is 100 meters in length when I do this, will it break?
3. If the rod is 1000 meters in length when I do this, will it break?
4. If the rod breaks, what length does it have to be before it
breaks, and at what point of the rod will the break occur?
5. If the rod is only 1 cm in diameter, does it break at a different
point or at a different length?
Thanks,
David


David, you are creating unnecessary complicated experiments, with the
most frequent flaw being an instantaneous speed change. It is of no
use that the speed change is small (in the "normal" range), as this
just make the error small. A small error can NOT be ignored when the
the length is huge. Huge length/small speed, small length/huge speed,
the problems don't go away.
In the problem I posted here the speed changes by 3 meters / second
over a 0.1 second interval. This is not an instantaneous speed
change. And from what I'm told, mechanical effects travel at the
speed of sound, so in a steel rod no mechanical effect can travel more
than 400 meters or so in the 0.1 seconds. So just what is the
instantaneous speed change you are referring to?
Thanks,
David

My advice to you is to understand the simple problems first, e.g. the
acceleration problem. You obviously haven't got to that point yet.
Acceleration is certainly not intuitive and has a few surprises
builtin, e.g. an event horizon and varying clock and acceleration
rates along the rod.

I'm thus not going to comment further on your complex problems, partly
due to your "reputation" among some of the "older" posters in the
group.

Kim

Kim B wrote:
On Sat, 27 Aug 2005 03:09:20 GMT, wrote:

Let's look at things with respect to the problem I posted, please post
your answer to the following questions.
1. If I place all points along the length of a steel rod 1 meter in
diameter and 10 meters in length onto a conveyer belt moving 3 meters
/ second, will the rod break?
2. If the rod is 100 meters in length when I do this, will it break?
3. If the rod is 1000 meters in length when I do this, will it break?
4. If the rod breaks, what length does it have to be before it
breaks, and at what point of the rod will the break occur?
5. If the rod is only 1 cm in diameter, does it break at a different
point or at a different length?
Thanks,
David


David, you are creating unnecessary complicated experiments, with the
most frequent flaw being an instantaneous speed change. It is of no
use that the speed change is small (in the "normal" range), as this
just make the error small. A small error can NOT be ignored when the
the length is huge. Huge length/small speed, small length/huge speed,
the problems don't go away.

My advice to you is to understand the simple problems first, e.g. the
acceleration problem. You obviously haven't got to that point yet.
Acceleration is certainly not intuitive and has a few surprises
builtin, e.g. an event horizon and varying clock and acceleration
rates along the rod.

I'm thus not going to comment further on your complex problems, partly
due to your "reputation" among some of the "older" posters in the
group.

Kim


I was working on a problem like that for a while... I never did quite
finish, though. I think I came to the conclusion that there wasn't an
event horizon. I kept going back and forth on the question at the
time.

http://www.spoonfedrelativity.com/files/myGravity7.swf
http://www.spoonfedrelativity.com/fi...onvelocity.swf

Actually, I think Dirk Van De Moortel gave me the mathematics I needed
to finish it...

http://groups.google.com/group/sci.p...0305e5d?hl=en&


.... but it was going to involve an almost complete rewrite. Performing
all the calculations of position and time of events in advance instead
of in real-time.

Anyway, I think it seemed resolved to me that t'(t) and x'(t) were
pretty well behaved functions, and no wierd event horizon effects
showed up under constant acceleration. Then I got sucked into the
bewilderment of Tensor Geometry, and never got around to working on it
anymore.

When you worked this, Kim, did you apply a 9.5 m/s^2 acceleration in
velocity or rapidity?

Just so everybody knows, I don't know rapidity from Sinh(rapidity).
Well, technically I do now. I just hate I think I know what a word
means and I use it all the time, and then find out it means something
totally different.

Okay, so Tanh(rapidity)=v/c is usually called Beta,
Cosh(rapidity)=1/sqrt(1-(v/c)^2) is usually called Gamma,
and Sinh(rapidity)=Beta*Gamma is proportional to momentum but does it
have a name?

http://www.spoonfedrelativity.com/files/TanhA.JPG

On 28 Aug 2005 15:14:41 -0700, "Spoonfed"
wrote:


Kim B wrote:
On Sat, 27 Aug 2005 03:09:20 GMT, wrote:

Let's look at things with respect to the problem I posted, please post
your answer to the following questions.
1. If I place all points along the length of a steel rod 1 meter in
diameter and 10 meters in length onto a conveyer belt moving 3 meters
/ second, will the rod break?
2. If the rod is 100 meters in length when I do this, will it break?
3. If the rod is 1000 meters in length when I do this, will it break?
4. If the rod breaks, what length does it have to be before it
breaks, and at what point of the rod will the break occur?
5. If the rod is only 1 cm in diameter, does it break at a different
point or at a different length?
Thanks,
David


David, you are creating unnecessary complicated experiments, with the
most frequent flaw being an instantaneous speed change. It is of no
use that the speed change is small (in the "normal" range), as this
just make the error small. A small error can NOT be ignored when the
the length is huge. Huge length/small speed, small length/huge speed,
the problems don't go away.

My advice to you is to understand the simple problems first, e.g. the
acceleration problem. You obviously haven't got to that point yet.
Acceleration is certainly not intuitive and has a few surprises
builtin, e.g. an event horizon and varying clock and acceleration
rates along the rod.

I'm thus not going to comment further on your complex problems, partly
due to your "reputation" among some of the "older" posters in the
group.

Kim


I was working on a problem like that for a while... I never did quite
finish, though. I think I came to the conclusion that there wasn't an
event horizon. I kept going back and forth on the question at the
time.

In the space-time diagram, any uniformly accelering object will have a
45° asymptote. Any events on the other side of this asymptote will
never be visible to the object


http://www.spoonfedrelativity.com/files/myGravity7.swf
http://www.spoonfedrelativity.com/fi...onvelocity.swf

Actually, I think Dirk Van De Moortel gave me the mathematics I needed
to finish it...

http://groups.google.com/group/sci.p...0305e5d?hl=en&


... but it was going to involve an almost complete rewrite. Performing
all the calculations of position and time of events in advance instead
of in real-time.

Anyway, I think it seemed resolved to me that t'(t) and x'(t) were
pretty well behaved functions, and no wierd event horizon effects
showed up under constant acceleration. Then I got sucked into the
bewilderment of Tensor Geometry, and never got around to working on it
anymore.

When you worked this, Kim, did you apply a 9.5 m/s^2 acceleration in
velocity or rapidity?

The acceleration is constant as viewed from the initial FOR

Kim

On Tue, 30 Aug 2005 10:35:48 +0200, Kim B wrote:

The acceleration is constant as viewed from the initial FOR

My mistake ... should be as viewed for the accelerating FOR, sorry

Kim

Kim B wrote:

In the space-time diagram, any uniformly accelering object will have a
45° asymptote. Any events on the other side of this asymptote will
never be visible to the object


Any event that can be seen by an inertial observer should also be seen
by a uniformly accelerating observer sitting right next to him, passing
him, or coming to a momentary rest adjacent to him.

If that conflicts with whatever you just said, you should let me know.

On 30 Aug 2005 09:11:50 -0700, "Spoonfed"
wrote:


Kim B wrote:

In the space-time diagram, any uniformly accelering object will have a
45° asymptote. Any events on the other side of this asymptote will
never be visible to the object


Any event that can be seen by an inertial observer should also be seen
by a uniformly accelerating observer sitting right next to him, passing
him, or coming to a momentary rest adjacent to him.

If that conflicts with whatever you just said, you should let me know.

An inertial observer will be able to see any event that happens, that
is just a matter of time. The accelerating observer will never see NO
events occuring on the other side of the asymptote (assuming, of
course, that he keeps accelerating).

Kim