Equivalence Principle

[EBTX] " ... the butt end of the rocket is always moving at a velocity which is always greater than the velocity of the weight ... "

In SR, maybe. But we already know SR is broken. So just add it to the list of dumb stuff that SR is famous for, and move on to something useful. (Oh, that's right. It's already on the list.)

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BTW, one of the "rules" for experimental attempts to verify the equivalence principle requires that you make your experiment smaller if you are able to tell the difference between the at-rest-on-the-surface condition and the accelerating-through-space-at-one-g condition.

How much smaller?

Just enough to make the detection go away.

Then you can stop the reduction operation.

Regards,
LB

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by EBTX</i>
<br />An important principle in GR is the equivalence between linear acceleration and gravitational acceleration. Has anyone seen this thought experiment anywhere ... or, have any ideas concerning it?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">This "equivalence principle" is of no importance in MM because Le Sage-type gravity is a force lacking inertia. Moreover, there is an experimental contradiction of the principle in the Greenberger-Overhauser neutron interferometer experiment.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Hence, the weight must gradually (and inexorably) move to the floor even though the force has the same constant value as in the gravitational model ... and ... one can then differentiate between gravity and linear acceleration from within this hypothetical laboratory (contrary to GR).<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Not so. The weight will stretch the thread until the elastic force in the thread brings the weight to rest with respect to the rocket.

The equivalence principle matches accelerations, not just speeds. Elastic forces will assure that both speed and acceleration are matched exactly. Assume the rocket fires thrusters with a 1g acceleration while it is still on Earth. Then the rocket would not lift off, but would remain in place with nothing changed, because its acceleration is just enough to overcome the pull of gravity and prevent falling, but not enough to start moving away from Earth.

Then if the Earth suddenly vanished, the rocket's 1g acceleration would allow it to start moving away from its former position, but the weight and thread would not notice any difference. This is all true in conventional physics, and does does not need relativity. -|Tom|-

On the subject of EP.

Given - a way to measure gravitational potential "locally" (IOW, without comparison to a reference potential.)

The gravitational potential field on the surface of Earth is substantially stronger than the gravitational potential field out in space.

Is there an effect of acceleration that would cause a potential meter to believe that there was a large mass nearby, when there is none? Or, might this be a way to falsify EP?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Larry Burford</i>
<br />Is there an effect of acceleration that would cause a potential meter to believe that there was a large mass nearby, when there is none? Or, might this be a way to falsify EP?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">It has always been true that a clock inside an elevator at rest and one in freefall will instantaneously tick at the same rate. The same is true for a rocket in space, whether accelerating or non-accelerating. Only speed and potential affect clock rates, but not force or acceleration.

But an observer inside an elevator could not tell whether clocks in the elevator ticked at one rate or another, and is not allowed to look outside (where he could easily see if the elevator was accelerating or not). -|Tom|-

Inverse Acceleration

The forces rally against me
Cause I say c^2 &gt; c
Yet Einstein showed me
The vacuum sea you see
But Dirac paid that fee
And all the powers are ours
For limitless infinite hours
Only the masses cower
At the mans lead shower
Sheople c^2 doubters
Massless displacement current
Turns the virtual fluids
Through elysiumæther purely
On hyper static surface
The E/m purpose is
Gods, martyrs, men, women
Law, order, chaos, sinning
Flat, curved, straight, spinning
Force, energy, power, friction
All own c^2 Omniscient witness

Copyright ©2004 Don Omni

[insert Saliva Survival of the Sickest]

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">
Not so. The weight will stretch the thread until the elastic force in the thread brings the weight to rest with respect to the rocket.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
No. The effect I am referring to is entirely relativistic.

Suppose that the weight has reached equilibrium as you say. Then ... the rocket continues to accelerate but the weight is not notified until the signal of continued acceleration reaches it some time (t) later. During "t", the butt end of the craft is logically constrained to move at a greater velocity than the weight (and must always do so) ... but this is in contradiction to the afforementioned equilibrium. The increased tension in the string cannot cause a signal through it to be transmitted at greater than c.

Hence, there is a genuine logical problem here with SR, GR and acceleration in general. Your counter example merely re-asserts the equivalence principle by stating that when the Earth vanishes and the rocket begins to move ... linearly ... it will be the same situation.

The string must increase in length until it breaks ... or ... the weight comes to rest on the floor of the ship ... or ... the weight oscillates along the line of acceleration at times going faster or slower than the rear of the ship. This last option is my personal guess but it is still different than a weight at rest in a gravitational field ... for, if it had a charge on it ... it would radiate electromagnetic energy which would not happen to a charged body at rest in a G-field.