Re: Are *observed* SR effects real?

On Jul 23, 6:19 am, mluttg...@xxxxxxxxxx wrote:
On Jul 22, 9:42 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:



On Jul 22, 1:04 pm, mluttg...@xxxxxxxxxx wrote:

On Jul 22, 7:08 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:

On Jul 22, 7:54 am, mluttg...@xxxxxxxxxx wrote:

On Jul 21, 11:57 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:

On Jul 21, 12:22 pm, mluttg...@xxxxxxxxxx wrote:

On Jul 21, 4:18 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:

On Jul 21, 7:37 am, mluttg...@xxxxxxxxxx wrote:

On Jul 21, 1:36 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:

On Jul 21, 3:34 am, mluttg...@xxxxxxxxxx wrote:

On Jul 21, 4:02 am, PD <TheDraperFam...@xxxxxxxxx> wrote:

A simple experiment shows that the train, not the ground,
is moving :
Tom used a spring scale on the ground. He put an object
on the scale, and found some weight w0.
On the train, he uses the same very precise spring scale.
If he measures w1 < w0 for the same object, he is *certain*
that the train is moving.

Why, Marcel, I'm astounded you still think it is possible to tell if
you are at a higher or lower absolute motion than in another frame.

Tell me, Marcel, in the plane flying east to west over a rotating
earth at 600 mph, what do you think the precise scales will show, and
why? And does this depend on whether it's noon or midnight? (Think
about where the plane is and what direction it must be going, relative
to the earth's motion in each case.) And does this depend on what time
of year it is? (Think about where the plane's direction will be,
relative to the solar system's motion relative to other stars.)

If I have *two* trains going by each other on *flat* tracks (not
following the curvature of the earth, but following a chord), do you
think it is possible to tell which one is going faster than the other
through space?

But trains do follow the curvature on the Earth!

Oh, dear. So Marcel, what do you think the answer is about the plane
that is flying east to west at 600 mph, hovering (at least in terms of
the sun-earth frame) in space while the earth rotates under it? Is the
plane *really* moving, and how can you tell?

What would do a plane whose engine cease working?

Eh? It's not a falling plane. It is traveling at 600 mph east to west
with respect to the ground, very much at full cruising speed. But it's
the earth that is sliding out from under the plane at 600 mph.
Compared to a line through the centers of the sun and the earth, the
plane is not moving.

Do you think it is impossible for a plane to travel at 600 mph east to
west with respect to the ground without falling out of the sky?
REALLY?

PD, can't you imagine that the engine suddenly stopped?

Eh?

Do you think it is impossible for a plane to travel at 600 mph east to
west with respect to the ground without the plane falling out of the
sky?

I spoke of an engine failure, why are you posing stupid
questions?

And that simultaneously (or do you think that the info
will be transmitted to the Earth at c?), the Earth will
cease sliding at 600 mph?

Accept the truth: SR is a purely geometrical construct!

Why would I accept something that is untrue. The physical foundations
for it are precisely what I've been explaining to you. There is not a
thing mathematically constructed in anything I've presented to you so
far.

You can claim that in its application domain, restricted
to so-called inertial frames, if A is considered to move
at v wrt B, B can be considered as moving at v wrt A.

Yes.

But don't claim that the Earth is moving wrt a cosmic
muon, or wrt a plane, etc...

Of course it is. As I just pointed out, you cannot tell from 600 mph
relative motion between the Earth and a plane, whether it is the plane
that's moving or the Earth that's moving. (And in fact, nothing
changes physically if both are, and so there is no physical value in
absolute motion.)

Ask your neighbour, if the Earth is chasing the plane.
Btw, how does the Earth physically know that if has
to move wrt some plane, but not wrt another one?
Because you decided it?

OK, Marcel, it is now plain that you cannot muster concentration
enough to follow an explanation of length contraction and time
dilation to its completion, and that your short attention span sends
you reeling off into the weeds first and then on into babbling.

This may have some relevance to why you are perpetually confused about
the very basics of relativity. It appears that if you can't have it
explained to you in a way that your wee little mind can capture it,
then you conclude there must be something wrong with it.

Do you want to continue with the plan you agreed to, or are you
confessing an insurmountable exasperation level?

PD

Marcel Luttgens

Don't be SR stupid.

Marcel Luttgens

And Marcel, you do realize, don't you, that we could have done this
whole exercise with Tom on one train and Stan on the other, with the
poles being on Stan's train and the brushes on Tom's train and filling
some other purpose, and the results of the simultaneity of the flashes
would have been exactly the same?

Finally, Marcel, if it wasn't clear, though virtually all reference
frames have either the effect of gravity or are falling some curved
trajectory in practical reality, it is also the case that in practical
reality many of those frames can be treated as inertial if the tidal
effects (read "non-inertial") are small enough to be ignored in the
measurement being taken. Small tidal effects are not the way to
determine which reference frame is the one that is "really" moving
(though it might provide some insight as to whether one of the frames
is in non-inertial motion).

A falling plane will reach the Earth with some
velocity vp, that can be calculated from its initial
height and the Earth's gravity.
Do you think that such plane can be considered as
being 'at rest', and the Earth is falling towards
the plane. Then calculate the velocity ve of the Earth
when it crashes into the plane. Do you think that
ve = vp?
Note that according to Newton's 3rd Law, the Earth
itself experiences an equal and opposite force to
that acting on the falling object, meaning that the
Earth also accelerates towards the object. However,
because the mass of the Earth is huge, the acceleration
of the Earth by this same force is negligible, when
measured relative to the system's center of mass.
(cf. Wikipedia,http://en.wikipedia.org/wiki/Gravity#Earth.27s_gravity
).
But SRists neglect Newton's 3rd law, and in fact,
all physical laws. They live in a very pecular world,
in which all frames are hypothesized to be 'inertial',
or practically inertial. For instance, in their thought
experiment, a train can move at 0.3 c without leaving
the rails!

Marcel Luttgens

Do you have any further comments or questions?

PD

Marcel Luttgens- Hide quoted text -

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You have been contradicting yourself!
You agreed that the domain of applicability of SR is limited
to 'inertial' frames.

Please pay attention to what I actually said. What I said is that
there are many frames that are not *absolutely* inertial, but in which
the non-inertial effects are much smaller than the effect being
measured and are therefore negligible (where "negligible" literally
means "can be neglected").

The curvature of the train tracks can be neglected because the effect
of that curvature is small compared to the size of the disagreement
about simultaneity being considered.

Moreover, the *gedanken* is designed to be an idealized situation and
not a real experiment. Where the verification of these principles has
occurred in *real* experiments, the design of the experiment has
rendered those noninertial effects truly negligible. If you want to
deal with real experiments only, I'm happy to start referring to, and
discussing the details of, a real experiment, but the explanation of
length contraction and time dilation will be much longer and much more
complicated.

Claiming that nothing changes physically when the Earth moves
wrt the plane is wrong, because the Earth is gravitationally
linked with the Sun (neglecting the Galaxy, and even the whole
Universe), and you should know that SR cannot be applied
in gravitational fields.

That is an incorrect statement. The GR principle of equivalence is
*precisely* the statement that, even in the presence of a
gravitational field, a small-enough laboratory in free-fall in a
gravitational field is *indistinguishable* from an inertial reference
frame. That's where it comes from.

And remember that trains follow the curvature of the Earth,
hence that trains and the objects they carry  are subject
to an acceleration a = v^2/R, where R is the Earth's radius.
Such acceleration is very small when v << c, but becomes
enormous when v is for instance 0.5 c, a value which is
comparable to the train velocity in your plan. I don't even
mention the fact that at such velocities, trains would leave
the solar system, and even the galactic system.

I would nevertheless be happy to continue with a physically
realistic plan, where SR applies.

Marcel Luttgens

.

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