A constant speed of light in all reference frames? Surely you can't be serious. [Physics]

Prev: Quantum Gravity 357.91: Croatia Shows That Probability of Vacuum Energy Density is More Important than its Vacuum Expectation Value (VEV) of the Hamiltonian Density, in line with Probable Causation/Influence (PI)
Next: Hubble Views Saturn's Northern/Southern Lights

From: Inertial on 4 Mar 2010 07:19

"Ste" <ste_rose0(a)hotmail.com> wrote in message
news:be65914d-1e32-4c41-a3a7-7037f34d53bb(a)c16g2000yqd.googlegroups.com...
> On 4 Mar, 09:39, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
> wrote:
>> "Ste" <ste_ro...(a)hotmail.com> wrote in message
>>
>> news:8984b4b4-92e9-466a-ad51-20e6b4e815bc(a)u9g2000yqb.googlegroups.com...
>> On 3 Mar, 22:23, "Inertial" <relativ...(a)rest.com> wrote:
>>
>>
>>
>>
>>
>> > "Ste" <ste_ro...(a)hotmail.com> wrote in message
>>
>> >news:64d02f70-01e4-44a5-a5ab-41429bf37f71(a)q15g2000yqj.googlegroups.com...
>>
>> > > I'm sure I said something about the ludicrous assertions that some
>> > > people here have made about the conceptual basis of SR. That is,
>> > > assertions that verge on meaningless, like "rotation into time" as an
>> > > explanation for length contraction. Or even observed time dilation
>> > > (in
>> > > SR) being "real" as opposed to merely a function of propagation
>> > > delays. But none of this fundamentally challenges SR.
>>
>> > Time dilation isn't anything to do with propagation delays .. they do
>> > NOT
>> > cause time dilation. It IS real in that it has been measured
>> > experimentally.
>>
>> > Your denial of reality is another trademark of a crackpot.
>>
>> I'm not denying it. I'm saying experiments that involve acceleration
>> are the realm of GR (as I understand it), and that acceleration is the
>> cause of "real" time dilation. We're talking about SR, and therefore
>> we cannot be talking about any experiment that involves acceleration.
>>
>> ________________________________
>> It is true that you cannot devise an experiment whereby two clocks are
>> together and then separated without at least one of them experiencing
>> acceleration at some point; that unfortunately is a mathematical fact,
>> not a
>> physical one.
>
> No, it is a physical fact.

It neither, as you can achieve such a synchronization without acceleration
during the process .. but it involves two additional clocks to make the
process work

>> However, you can make the contribution of acceleration "vanishingly
>> small",
>> by designing thought experiments where the accelerations are very low and
>> slow. Sending a rocket to another star is one such example.
>
> Not really, because if the total acceleration is small, then so is the
> speed.

That is a nonsense argument. Acceleration can be small and speeds very
large.

>> You now appear to be claiming that you *don't* believe the twins will be
>> different ages due to simple time dilation in SR, which means you *don't*
>> agree that SR is correct.
>>
>> So, yet again, like the uber-crank you are, you have completely changed
>> your
>> story.
>>
>> Yesterday you believed in the predictions of SR. Now you say you don't.
>>
>> Its called *inability to learn*.
>
> <yawn>

Yeah .. yawn away .. and remain a fool

From: Inertial on 4 Mar 2010 07:33

"Peter Webb" <webbfamily(a)DIESPAMDIEoptusnet.com.au> wrote in message
news:4b8f8d23$0$24251$afc38c87(a)news.optusnet.com.au...
>
>
>>> I'm not denying it. I'm saying experiments that involve acceleration
>>> are the realm of GR (as I understand it), and that acceleration is the
>>> cause of "real" time dilation. We're talking about SR, and therefore
>>> we cannot be talking about any experiment that involves acceleration.
>>>
>>> ________________________________
>>> It is true that you cannot devise an experiment whereby two clocks are
>>> together and then separated without at least one of them experiencing
>>> acceleration at some point; that unfortunately is a mathematical fact,
>>> not a physical one.
>>
>> No .. you can do that without acceleration. But it involves multiple
>> clocks.
>>
>>
>
> Well, I put it to you that acceleration is the second derivative of
> position

You can put that all you like :):)

> ....
>
> There is one way you can get close. You could have clock circling the
> earth in a plane, and flying past some reference clock fixed to the earth,
> and compare times when they are close.

If it is going in a circle, it is accelerating.

> Unfortunately though it could be argued correctly that the flying clock is
> actually accelerated more, because it circles the earth faster,
> effectively the additional centrifugal force reduces the measured force of
> g in the plane, and I suspect that the nett effect is the opposite to that
> predicted by SR - a very slight increase in the rate at which time passes.
> I could be wrong.
>
> However, I stress that these effects of GR are typically many orders of
> magnitude lower than those from SR, and it is obviously very hard to
> design experiments which even show the GR effects, the SR ones are so
> dominant, and now a standard part of engineering.

Not in a GPS satellite .. the effects due to difference in gravitational
potential (GR) outweigh the SR effects.

> I am sure you are aware that GPS satellites have to compensate for both SR
> and GR. It is interesting though that these are for vastly different
> reasons. SR causes the effects you would expect on the accuracy of the
> clocks, but GR's effect is mostly not through time dilation but rather
> through directly affecting the orbit of the satellite.

Regarding the clock sync issue ...

A way to get separated clock sync without acceleration during the process.

A--->
C1 C C2
<---B
Have two clocks (A and B) already in motion (before you start the sync
process) moving in opposite directions at equal speeds and distances from a
common point c, where they will pass each other

When the meet, synchronise their clocks as they pass (no stopping)

A--->
C1 C C2
<---B

As they continue on their way they each pass two other clocks, C1 and C2,
and sync with those as they pass

A--->
C1 C C2
<---B

Clocks C1 and C2 are now synchronized, effectively in the same way as slow
clock movement.

You only need acceleration if the two moving-apart clocks are initially at
REST when they are synced together and if they come to REST when they reach
the extremes. having them in motion already avoids the initial acceleration
from rest, and using two additional clocks (C1 and C2) avoids deceleration
when to come to rest.

From: mpalenik on 4 Mar 2010 08:40

On Mar 4, 3:12 am, Ste <ste_ro...(a)hotmail.com> wrote:
> On 3 Mar, 20:01, mpalenik <markpale...(a)gmail.com> wrote:
>
> > On Mar 3, 12:52 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > > No. In SR, clocks *appear* to run slower as you are increasing your
> > > distance from the clock. The effect is entirely apparent in SR.
>
> > You must just go through the entire thread and not pay any attention
> > to what anybody says. Ever.
>
> > 1) What you've stated above is not an effect of SR. It is an effect
> > of propagation delay, which was used to calculate c from the motion of
> > the moons of jupiter hundreds of years ago.
>
> Ok.
>
> > 2) If you were to move TOWARD the clock, it would appear to run
> > faster. But SR says nothing about whether you are moving toward or
> > away from an object.
>
> <suspicious eyebrow raised> Ok.
>
> > 3) The amount that the clock would appear to slow down is DIFFERENT
> > from the amount that SR predicts the clock *actually* slows down
>
> Really? I'm growing increasingly suspicious. In what way does SR
> predict the "actual" slowdown, as opposed to the "apparent" slowdown?
> And for example, if we racked up the value of 'c' to near infinity,
> would SR still predict an "actual" slowdown, even though the
> propagation delays would approach zero?

With what you have described, I checked just to be sure, even though I
was already pretty sure what the answer would be, the time you read
moving away the clock would be:

t2 = t - (x+vt)/c = t(1-v/c) - x

and when you move toward the clock

t2 = t + (x+vt)/c = t(1+v/c) + x

so moving away from the clock:
dt2/dt = 1-v/c
and toward
dt2/dt = 1-v/c

Special relativity predicts that the moving clock will always slow
down as
dt2/dt = sqrt(1-v^2/c^2)

What you *measure* is a combination of the actual slow down predicted
by SR (sqrt(1-v^2/c^2) and whatever changes occur due to propagation
delays (which depend on the direction of motion).

>
> > 3) This does not explain why atomic clocks on a jet register different
> > times AFTER being brought to rest than do their counterparts which
> > have been at rest the entire time--or why the difference in time that
> > they register is exactly consistant with the predictions of
> > relativity.
>
> Indeed, because SR doesn't deal with acceleration.

SR deals with acceleration just fine. GR is only needed to describe
gravity.

I'll explain the thought experiment I posted later but I have to teach
in less than an hour.

From: Ste on 4 Mar 2010 10:19

On 4 Mar, 12:19, "Inertial" <relativ...(a)rest.com> wrote:
> "Ste" <ste_ro...(a)hotmail.com> wrote in message
>
> > Not really, because if the total acceleration is small, then so is the
> > speed.
>
> That is a nonsense argument. Acceleration can be small and speeds very
> large.

When I went to school, you could not have a large change of speed with
only a small amount of total acceleration.

From: Ste on 4 Mar 2010 10:31

On 4 Mar, 13:40, mpalenik <markpale...(a)gmail.com> wrote:
> On Mar 4, 3:12 am, Ste <ste_ro...(a)hotmail.com> wrote:
>
>
>
>
>
> > On 3 Mar, 20:01, mpalenik <markpale...(a)gmail.com> wrote:
>
> > > On Mar 3, 12:52 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > > > No. In SR, clocks *appear* to run slower as you are increasing your
> > > > distance from the clock. The effect is entirely apparent in SR.
>
> > > You must just go through the entire thread and not pay any attention
> > > to what anybody says. Ever.
>
> > > 1) What you've stated above is not an effect of SR. It is an effect
> > > of propagation delay, which was used to calculate c from the motion of
> > > the moons of jupiter hundreds of years ago.
>
> > Ok.
>
> > > 2) If you were to move TOWARD the clock, it would appear to run
> > > faster. But SR says nothing about whether you are moving toward or
> > > away from an object.
>
> > <suspicious eyebrow raised> Ok.
>
> > > 3) The amount that the clock would appear to slow down is DIFFERENT
> > > from the amount that SR predicts the clock *actually* slows down
>
> > Really? I'm growing increasingly suspicious. In what way does SR
> > predict the "actual" slowdown, as opposed to the "apparent" slowdown?
> > And for example, if we racked up the value of 'c' to near infinity,
> > would SR still predict an "actual" slowdown, even though the
> > propagation delays would approach zero?
>
> With what you have described, I checked just to be sure, even though I
> was already pretty sure what the answer would be, the time you read
> moving away the clock would be:
>
> t2 = t - (x+vt)/c = t(1-v/c) - x
>
> and when you move toward the clock
>
> t2 = t + (x+vt)/c = t(1+v/c) + x
>
> so moving away from the clock:
> dt2/dt = 1-v/c
> and toward
> dt2/dt = 1-v/c
>
> Special relativity predicts that the moving clock will always slow
> down as
> dt2/dt = sqrt(1-v^2/c^2)
>
> What you *measure* is a combination of the actual slow down predicted
> by SR (sqrt(1-v^2/c^2) and whatever changes occur due to propagation
> delays (which depend on the direction of motion).

Ok. So let us suppose that we take two clocks. Separate them by a
certain distance, synchronise them when they are both stationary, and
then accelerate them both towards each other (and just before they
collide, we bring them stationary again). Are you seriously saying
that both clocks report that the other clock has slowed down, even
though they have both undergone symmetrical processes? Because there
is obviously a contradiction there.