SR and one-way light speed tests

Mac,

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Did you see the string I posted regarding the Unruh Affect? Acceleration has been found to create real particles from virtual particles using the energy of the accelerating observer.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

I'm sorry, haven't seen your string on the Unruh Effect. But like you say, if we assume that merely acceleration causes changes of state, then the virtual to real particle converion sounds like a real possibility. After all, we are dealing with particle accelerators: SR cannot even be used in this case since we do not have uniform motion in the accelerator.




Enrico,

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">By the way, there is no such thing as an accelerometer measuring acceleration directly. All is measured is position and twice -differentiated in time using sophisticated algorithms. No way to measure acceleration or even velocity directly in a world in which the only things that are fundamental quantities are distance, time and mass(?).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Mind you, we do NOT differentiate in engineering applications as to obtain a velocity from the accelerometer. Indeed, we *integrate* instead. It is often the case that one uses a first-order filter to take a "dirty derivative", but when the signal is noisy, the approximation is bad. However, mathematically speaking, integration can be called to be a "smoothing operation": it is perfecly possible to integrate a discontinuous function.

In fact, they use accelerometers in the some cars like BMW and Mercedes for their controller design, such as traction control. Albeit expensive, accelerometers are very useful.


<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Pick your choice:

Absolute velocity - absolute acceleration: Newton

Relative velocity - absolute acceleration: Post-Newtonians

Relative velocity - relative acceleration: Liebniz

Absolute velocity - relative acceleration: Leibniz (?)<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">


Since no backgound has been detected, I'd go for the relative velocity , the acceleration can be taken to be relative and absolute simultaneously.

When an object is far away from celestial bodies, there is absolute no reason for relativistic phenomena to take place by uniform motion in void space. Whether there is an observer or not. I do not believe that uniform motion can slow my clock if space is void. The symmetry in SR is a logical fallacy.

On the other hand, when my top-notch capacitive accelerometer gives me a reading, then I know that something is happening. In this case one can expect that states of the system may experience change. In void space, the acceleration can only cause incremental change. Since no backgound exists, my velocity is irrelevant, but acceleration can be easily detected. Absolute or relative acceleration is pathalogical. I believe that as soon as one accelerates, a frame is defined: the one left behind just before acceleration.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">The question I pose then here is the following: What's you favored space-time structure? (and that's the end of it).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Sorry, I have no familiarity with space-time structures, although some with general tensor algebra.

"It only takes one white crow to proof that not all crows are black."

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jan</i>
<br />Mac,

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Did you see the string I posted regarding the Unruh Affect? Acceleration has been found to create real particles from virtual particles using the energy of the accelerating observer.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

I'm sorry, haven't seen your string on the Unruh Effect. But like you say, if we assume that merely acceleration causes changes of state, then the virtual to real particle converion sounds like a real possibility. After all, we are dealing with particle accelerators: SR cannot even be used in this case since we do not have uniform motion in the accelerator.




Enrico,

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">By the way, there is no such thing as an accelerometer measuring acceleration directly. All is measured is position and twice -differentiated in time using sophisticated algorithms. No way to measure acceleration or even velocity directly in a world in which the only things that are fundamental quantities are distance, time and mass(?).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Mind you, we do NOT differentiate in engineering applications as to obtain a velocity from the accelerometer. Indeed, we *integrate* instead. It is often the case that one uses a first-order filter to take a "dirty derivative", but when the signal is noisy, the approximation is bad. However, mathematically speaking, integration can be called to be a "smoothing operation": it is perfecly possible to integrate a discontinuous function.

In fact, they use accelerometers in the some cars like BMW and Mercedes for their controller design, such as traction control. Albeit expensive, accelerometers are very useful.


<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Pick your choice:

Absolute velocity - absolute acceleration: Newton

Relative velocity - absolute acceleration: Post-Newtonians

Relative velocity - relative acceleration: Liebniz

Absolute velocity - relative acceleration: Leibniz (?)<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">


Since no backgound has been detected, I'd go for the relative velocity , the acceleration can be taken to be relative and absolute simultaneously.

When an object is far away from celestial bodies, there is absolute no reason for relativistic phenomena to take place by uniform motion in void space. Whether there is an observer or not. I do not believe that uniform motion can slow my clock if space is void. The symmetry in SR is a logical fallacy.

On the other hand, when my top-notch capacitive accelerometer gives me a reading, then I know that something is happening. In this case one can expect that states of the system may experience change. In void space, the acceleration can only cause incremental change. Since no backgound exists, my velocity is irrelevant, but acceleration can be easily detected. Absolute or relative acceleration is pathalogical. I believe that as soon as one accelerates, a frame is defined: the one left behind just before acceleration.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">The question I pose then here is the following: What's you favored space-time structure? (and that's the end of it).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Sorry, I have no familiarity with space-time structures, although some with general tensor algebra.

"It only takes one white crow to proof that not all crows are black."
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

It makes sense that acceleration would define a frame since that's
when energy transfers occur.

Jan,

You might find this of interest. Unruh Affect.

http://www.theorie.physik.uni-muenc...SS03-T6-LN8.pdf

Knowing to believe only half of what you hear is a sign of intelligence. Knowing which half to believe can make you a genius.

1234567890:

Mind you, we do NOT differentiate in engineering applications as to obtain a velocity from the accelerometer. Indeed, we *integrate* instead. It is often the case that one uses a first-order filter to take a "dirty derivative", but when the signal is noisy, the approximation is bad. However, mathematically speaking, integration can be called to be a "smoothing operation": it is perfecly possible to integrate a discontinuous function.


The devices you refer to are called transducers and there are many kinds, like piezoelectric, capacitive, spring-mass, etc. Those devices DO NOT measure velocity or acceleration directly but tranduce such kimenatic quantities to voltage, usually. A calibration technique and possible feedback loop must be used to stabilize such devices, which are intended for law accuracy applications. It is important to understand that NO measure of acceleration or velocity is made directly but the EFFECT of these are detected via the physical properties of the tranducer.

Modern gravimeters employ interferometers and a position versus time graph of a free falling body is plotted. From this graph the value of g is determined. These techniques measure position versus time. See the following link for information on modern techniques used in gravimeters:

www.microgsolutions.com/index.html

Mind you, but I have no idea how to measure velocity or acceleration directly, exept through a tranducer or via a position versus time plot and then taking the slope. If you know such a technique, you can qualify for the next Nobel price and I'll be happy for you. All I can do is measure relative position and relative time interval by a clock.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Enrico</i>

Mind you, but I have no idea how to measure velocity or acceleration directly, exept through a tranducer or via a position versus time plot and then taking the slope. If you know such a technique, you can qualify for the next Nobel price and I'll be happy for you. All I can do is measure relative position and relative time interval by a clock.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Is it really that hard to believe that I can measure acceleration and integrate to get the velocity and position? Obviously, you are not aware of the current state of technology.

Let me see, according to newton, we have F=m*a. So if I take F=k*x for my spring inside, then I get

a = (k/m)*x.

Here x is the displacement within my top-notch accelerometer, which can be measured in various ways very easily. From here we can easily integrate to get our velocity. So no diagrams and slope plots are required. Once again, we really do not need to differentiate whatsoever: accelerometers were designed to avoid this since differentiation is inherently noisy.



"It only takes one white crow to proof that not all crows are black."

Jan: Is it really that hard to believe that I can measure acceleration and integrate to get the velocity and position? Obviously, you are not aware of the current state of technology.

I gave you a link about the current state of the art. You refer to high school experiments. Differentiation was a noisy affair back in the days of Galileo. There is progress since then. If you read the link you will find out how these devices limit noise down to nothing.

Your equation is an idealization that can hardly measure acceleration or velocity to more than 3 significant digits but to hysterises and other non-linear effects of the transducers.

As an example, modern high-speed robotic systems use advanced feedback control using pulses of the angle of the arms from digital encoders and these controllers feedback velocity and acceleration to stabilize dynamics and even correct for Coriolis coupling of the arms, and the quantities of velocity and acceleration are derived by differentiation of the position signal, and position is the only thing measured directly.