Kopeikin and "the speed of gravity"

From the Market Stop:

Would you care for a punch?

---

Actually I just came back from the dojo I'm an instructor of Shorin-Ryu part-time. lol

Puncing is the act of inducing momentum to another person's body. For the punch to be effective, the contact time must be as short as possible to avoid an elastic collision. The transfered momentum excites the nerves and organs of the opponent and under many circumstances also induces angular acceleration to his body parts and joints causing extreme pain.

Where do you see a force involved in punching?

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[JBailey]: The design of the gravimeter, as I understand it, is to measure a falling weight at 1MHz intervals.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Suppose we set up a rapidly oscillating source in Walker-Dual fashion. It might be a weight propelled at high speed around a circular track. Then we need only measure any delay in the phase of the gravitational force arriving at the gravimeter. But how large a mass is needed? We need to know the sensitivity of the gravimeter.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[JBailey]: Does anyone understand whether Walker and Dual have published the results of their vibrating rod experiments? Perhaps we are simply retracing old ground on this<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Their results for gravity are ambiguous because they confuse the phase of the oscillating source with the "phase speed of gravity". But gravity has no phase speed if it is not a wave phenomenon.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[mechanic]: What is "speed of a force?" More importantly, what is a force?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

It is common usage to speak of the "force" of gravity, meaning F = m*a. Of course, what we really measure is the 3-space acceleration of gravity. And the speed we are interested in is how quickly changes in the direction or distance of a source mass are reflected in corresponding changes in the direction or strength of the acceleration of the gravimeter or target body.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[mechanic]: I haven't seen any equation in any physics book involving a speed of a "force". Force is thought to be the cause of acceleration, or vice versa. What then if someone asks; what's the speed of acceleration?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

This is correct. We seek the speed of transfer of cause (at the source mass) to effect (at the target body). Technically, forces and accelerations don't have speeds. However, the acceleration of the target body is the result of momentum changes, whether those are continuous or consist of innumerable discrete impulses. The acceleration is just the sum of all the momentum changes made to the target body. And momentum has a speed and a direction.

[mechanic]: The closest those gravimeters can get is measuring potential disturbance speed, which is equal to c.

The potential field has no effect on the motion of a target body or on a gravimeter. It will cause light to bend, atomic clocks to slow, etc. It is most easily thought of as "aether", "space-time medium", "elysium", or various other words for basically the same phenomenon. LIGO will consider itself fortunate to merely detect changes in a gravitational potential field, let alone measure its speed.

Let's stick to measuring gravitational "force", which is the dominant force by far in the solar system and easily detected by gravimeters. -|Tom|-

From Tom:

The acceleration is just the sum of all the momentum changes made to the target body. And momentum has a speed and a direction.

Let's stick to measuring gravitational "force", which is the dominant force by far in the solar system and easily detected by gravimeters.

---

Momentum is mass times velocity. Momentum has magnitude and direction for it being a vector. I don't understand the statement "momentum has velocity". Is this new Physics? If a function P is defined as P= mv then we say P is m times v or v if the domain and mv is the range of P. We never say P has v. First time I hear that and it sounds "bad". I'm sorry to say this.

I was reading older posts and Tom argued Jim to forget about forces because if one starts thinking about it all kinds of contradictions can arise (can't find the post but it must be somewhere in here). Now Tom is talking about forces as predominant and Newton's second law. Well, make up your mind people what kind of Physics you're doing. One shouldn't be that selective jumping from model to model according to his own desire and ability to explain reality.

Gravimeters measure rate of fall and this is done by differentiating discrete sampled position measured by interferometers. Force is not measured, force is calculated if one assumes Newton's law applies. Understanding the difference between what is measured and what is calculated is very important in this case. There is no way to deduce speed of gravity or speed of force from gravimeters simply because there is no mathematical model for it. It is assumed infinite. If it were finite, you would have to measure force directly to calculate its time response. Such measurement is impossible using laser interferometers. One must find a way to measure force directly and a lot faster than its transmission speed. Which is impossible. It's like measuring speed faster than the position it defines.

"what aru you doing? why are you doing it? time is passing!", Wilhelm Gottfried Leibniz (I hope you understand what it means)

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote> [tvf]: Suppose we set up a rapidly oscillating source in Walker-Dual fashion. It might be a weight propelled at high speed around a circular track. Then we need only measure any delay in the phase of the gravitational force arriving at the gravimeter. But how large a mass is needed? We need to know the sensitivity of the gravimeter.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

I'm appreciative of Tom's interjections and clarifications. I was inspired by <i>AgoraBasta</i> to think of off-the-shelf equipment to test the hypothesis that "g" travels much faster than c. If we can measure the rate, we can reject the hypothesis. (With apologies to <i>mechanic</i>, I don't mean to be imprecise; I simply seek a way to detect any distance-related latency in the propagation of gravitational attraction among masses. I infer that he accepts this rate is c. That seems slow enough that we ought to be able to cobble together some equipment to confirm it.)

So, perhaps we could return to the proposal by <i>AgoraBasta</i> (10 Jan 17:32:30). It sounds straightforward but no one spoke up as having access to the required crystals. I assume he has some experience. Can we get a sufficiently massive chunk of quartz to oscillate at several GHz? Is there agreement that his design will measure the right effects (and not, for example, EM or electrostatics)? I wonder if we could do without the excitation spike and simply observe the change in relative phases between the excited and resonant crystals as the distance between them is varied. (This may be Tom's idea in the above quote.)

I'm open to any design as long as it is feasible and cheap (the Holy Grail of empiricists)!

While I was composing the last post, <i>mechanic</i> posted the comment that seems to say the speed of gravity is assumed to be infinite:
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote> There is no way to deduce speed of gravity or speed of force from gravimeters simply because there is no mathematical model for it. It is assumed infinite. <hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote> So, I may have been wrong previously to infer that he maintains that the speed of attractive gravitational effect is c.

It may not have been clear before that my earlier proposal was to use two gravimeters to measure the latency of the attractive effect of a gravitational disturbance as a function of the distance between them. Or, we may be simply talking past each other as often happens in these fora!

From JBaily:

So, I may have been wrong previously to infer that he maintains that the speed of attractive gravitational effect is c.

---

The speed of gravity is infinite and the speed of gravitatonal potential disturbances is c. This must be true in order to preserve causality. Now, AgoraBasta is right saying potentials are not real. They are just mathematical models from which gravitational accelerations are derived. The change in these accelerations propagate at the speed of light, in my opinion.

To measure the speed of gravity an appropriate mathematical model of it is required. All we can measure is 3-D position vectors, mass and time. These are the three fundamental quantities in Physics. Some books call force a fundamental quantity but they are flat wrong. Anything else is infered via mathematical models. Velocity and acceleration are deduced from position and time via integration and force is mass times acceleration.

In Pushing gravity, gravity and graviton speed is the same. If a chunk of a planet magically dissappears, the gravitons pushing it will go away with it and the disturbance must propagate at the speed of gravitons coming from the sun, now finding less mass to play with. Then, "force or pressure" changes are happening at the speed of the gravitons, which essentially defines mathematically the speed of gravity, being its transmission medium.

If Kopeikin is right then gravitons don't exist and gravity is just a geometric effect with a speed equal to c. This does not violate anything since there are no forces present and no torques can result from a time delay in their transmission.

In order to disprove Kopeikin one must measure changes in falling rate due to a disturbance in the gravity potential. Speed of light is in the order of 10^8 m/s and the mass of the earth in the order of 10^24 Kg. Measuring the speed of gravity at these orders when your falling mass and disturbing mass is in the order of a few grams or Kg is impossible. A way to magnify the effect must be found without an excitation or modulating electrical signal. It must be a pure disturbance in gravitational attraction and the change in the falling rate, the third derivative of position with respect to time will give the answer.

Big discoveries require big disturbances. "...Time is passing", W.G.L