-----Original Message-----
From: pma15027@xxxxxxxxxxxxxx
Sent: Sat, 10 May 2008 10:01:13 +1000Well Neville I must say this post from you surprised me.. you say,"Einstein taught us that gravity and acceleration are one and the same."
If this is true, then he turned definitions of physics upside down and into a joke..The terms gravitation and gravity are mostly interchangeable in everyday use, but in scientific usage a distinction may be made. "Gravitation" is a general term describing the attractive influence that all objects with mass exert on each other, while "gravity" specifically refers to a force that is supposed in some theories (such as Newton's) to be the cause of this attraction. By contrast, in general relativity gravitation is due to spacetime curvatures that cause inertially moving objects to accelerate towards each other.Thus to start with, relativity is using the distinct term gravitation not gravity.But you then say "THAT IS THE EQUIVALENCE PRINCIPLE" and again, is perfectly correct.How can anyone get "equivalence" to mean ONE AND THE SAME , or are the same?Thats like saying that because cheese and beans are equivalent protein foods, that they are the same.. Which obviously they are not. We can or may say the Geocentric and heliocentric systems are dynamically equivalent, but NEVER are they the same.In any case, Paul and myself were not quoting relativity physics, in this discussion with Allen over an accelerometer which IS a different physics. But thats beside the point.. I am forced to examine what Hindstein did say.According to wiki in a nutshell..In the physics of relativity, the equivalence principle refers to several related concepts dealing with the equivalence of gravitational and inertial mass, and to Albert Einstein's assertion that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is actually the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.
"In the physics of relativity" obviously points to a different physics .....BUT from this paragraph it seems obvious to me that He is not saying that gravity and inertia are the same thing but , now listen carefully,
But that the FORCE the gravitational force, is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.,
I take that to mean the forces are equivalent, like as the protein in beans and cheese.. But that Beans aint cheese , and gravity aint inertia still hold...
In any case, the equivalence principle is based on this FALSE PRESUMPTION,
Today the notion of "absolute space" is abandoned, and an inertial frame is defined
To me in some respects this is WORSE than denying God.. Because it denies basic common sense.. Its like saying one must deny the existence of mental telepathy because they cannot duplicate it, or find it . or make it.. Therefore I would not, and could not intertain any thought of accepting such erroneous principle based upon a basic precept of the non-existence of absolute space. By the way, I take Absolute space in this context to mean a place of absolute non-motion.. The relativity people mean it to mean "absolute time and space"
A real concoction that one, yet one I'm partial to in my own way of course.
It has to be acknowledged that IF reality is four dimensional, then all the rules get bent.. That is a big IF..
And in any case there are at least four equivalence principles .. http://en.wikipedia.org/wiki/Equivalence_principle
Philip
for nit picky:
The equivalence principle emerged in the late 16th and early 17th centuries, when Galileo showed experimentally that the acceleration of a test mass due to gravitation is independent of the amount of mass being accelerated, thereby refuting Aristotle. These findings led to gravitational theory, which concludes that inertial and gravitational masses are identical...
Note the masses are identical, not the definitive meaning of gravity and inertia.
The equivalence principle proper was introduced by Albert Einstein in 1907, when he observed that the acceleration of bodies towards the center of the Earth at a rate of 1g (g = 9.81 m/s2 being the acceleration of gravity at the Earth's surface) is equivalent to the acceleration of an inertially moving body that would be observed on a rocket in free space being accelerated at a rate of 1g. Well of course! we called it artificial gravity! But rest assured, changes in gravity due to near massive bodies will not be detected by people on the earth, whereas a change in the motor power accelerating the rocket will throw the passengers around the room.
Notice again, the accelerations are equivalent, not the meaning of gravity or inertia..
However Wiki then expresses an opinion, or a hope perhaps, but wrong none the less.
Today the notion of "absolute space" is abandoned, and an inertial frame is defined
yet still conclude, "So the original equivalence principle, as described by Einstein, concluded that free-fall and inertial motion were physically equivalent. "
Notice the equivalence of motions, not saying the terminology gravity is the same as inertia.
Not anywhere have I found a denial of these basic definitions. Gravity.. and inertia.
Does Einstein or Allen or anyone deny these definitions as referring to two entirely different conditions, and that they still be true.
The terms gravitation and gravity are mostly interchangeable in everyday use, but in scientific usage a distinction may be made. "Gravitation" is a general term describing the attractive influence that all objects with mass exert on each other, while "gravity" specifically refers to a force that is supposed in some theories (such as Newton's) to be the cause of this attraction. By contrast, in general relativity gravitation is due to spacetime curvatures that cause inertially moving objects to accelerate towards each other.
INERTIA
Definition 3 of his Philosophiae Naturalis Principia Mathematica, which states:[1]
The vis insita, or innate force of matter is a power of resisting, by which every body, as much as in it lies, endeavors to preserve in its present state, whether it be of rest, or of moving uniformly forward in a right line.
In common usage, however, people may also use the term "inertia" to refer to an object's "amount of resistance to change in velocity" (which is quantified by its mass), and sometimes its momentum, depending on context (e.g. "this object has a lot of inertia"). The term "inertia" is more properly understood as a shorthand for "the principle of inertia as described by Newton in Newton's First Law of Motion which, expressed simply, says: "An object that is not subject to any outside forces moves at a constant velocity, covering equal distances in equal times along a straight-line path." In even simpler terms, inertia means "A body in motion tends to remain in motion, a body at rest tends to remain at rest."
END OF SELECTIONS of modern confusion.
