Re: Hobba's misconceptions


"Mike" <eleatis@xxxxxxxx> wrote in message
news:1134185604.333544.88940@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> here you go:
>
> http://groups.google.com/group/sci.physics/msg/1694d44358577f35
>
> and I quote his gem (another one):
>
> "Newton's First Law contains implications about the
> fundamental symmetry of the universe in that a state
> of motion in a straight line must be just as
> "natural" as being at rest. If an object is at rest in one frame of
> reference, it will appear to be moving in a straight line to an
> observer in
> a reference frame which is moving by the object. There is no way to say
>
> which reference frame is "special", so all constant velocity reference
> frames must be equivalent.'

The above, while basically correct, was not written by me.

>
> Thus, contrary to your irrational assertions that classical mechanics
> requiring an absolute frame, Newton's first law in fact asserts the
> opposite. What classical mechanics has is the notion of absolute time.
> "

Yea I did write that.

>
> end quote
>
> Now, Hobba seems to have never understood Newtonian mechanics (amybe he
> never took a course). In fact, Newton's famous backet
>

I suspect bucket means bucket.

> experiment was
> about showing that there is an absolute frame of reference.

That experiment shows no such thing. See Tom Roberts excellent analysis:
http://groups.google.com/group/sci.physics.relativity/msg/d157eb4b0462c947?dmode=source

> Hobba does
> not understand that when curvilinear motion comes into play, his silly
> argument breaks down. Consider the following REAL experiment, not the
> type of though experiments he has been brainwashed with:
>
> On a rotaing disk there is a spring attached to its center and a steel
> ball attached to its other end, resting on the disk. When we start
> rotate the disk uniformly, the spring extends by a small distance
> delat(x). The ball now is at rest in its own frame of reference.

Any object is at rest in some frame. In this case it is non inertial, and
is subject to forces of acceleration.

> According to Hobba:
>
> "If an object is at rest in one frame of reference, it will appear to
> be moving in a straight line to an observer in a reference frame which
> is moving by the object. There is no way to say
> which reference frame is "special", so all constant velocity reference
> frames must be equivalent.'

Of course I never wrote that - but let us ignore your appalling scholarship
for the moment - the above is about inertial frames.

>
> Well, I will tell you which frame is special. For a stationary observer
> in the room the disk is located, the for e registered by the spring is
> equal to the centripetal force that keeps the ball in circular motion.
> But in the disk frame, it is at rest although there is a force measured
> by the spring. This means, contrary to the knowledge you have acquired
> by various web pages, that the laws of motion (which you do not
> understand) must be applied in the right frame.
>

In classical mechanics every inertial frame will measure exactly the same
force.

> And this was exactly
> Newton's point. In order to explain how come the ball is at rest in its
> own frame while there is a force on it, a ficticious centrifugal force
> must be considred. Newton said: "Ficticious forces arise because of the
> applications of the laws of motion in the wrong reference frame". What
> is the correct reference frame? It is absolute space. Now, everybody
> knows this, but you do not. This is because, all your knowledge comes
> from the web.
>
> Thus, kinematically (that is probably the only introductory course
> Hobba took) all constant velocity frames are equivalent. But when
> forces come into play, in Newtonian Mechanics the second can be applied
> only wrt an absolute frame of reference.

The Galilean transformations of classical mechanics imply otherwise. Study
Landau - Mechanics then repost.

Bill

>
> The conclusion is that Hobba is a very confused fellow who plays
> relativity expert but he does not understand that from the first law of
> Newton, which does not require a special frame, he cannot claim the
> same when forces come into play. Actually, LEX PRIMA (first law) is
> about the fact that relativity of motion applies only in kinematics but
> when forces come into play as in LEX SECUNDA (second law), relativity
> breaks down and the notion of an abslute space comes in. This is
> exactly what Mach tried to challenge and Einstein failed to incorporate
> his views in GR and as a result, GR HAS AN ABSOLUTE SPACE-TIME wrt
> which deviations from geodesic paths must be referenced.
>
> Mike
>


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