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

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From: G. L. Bradford on 11 Mar 2010 12:10

"Peter Webb" <webbfamily(a)DIESPAMDIEoptusnet.com.au> wrote in message
news:4b98cae0$0$11705$afc38c87(a)news.optusnet.com.au...
>
> "Inertial" <relatively(a)rest.com> wrote in message
> news:4b98c72d$0$8803$c3e8da3(a)news.astraweb.com...
>>
>> "G. L. Bradford" <glbrad01(a)insightbb.com> wrote in message
>> news:WaidncSioueeWwXWnZ2dnUVZ_sudnZ2d(a)insightbb.com...
>>> Planet A and planet B are similar planets one light year apart. A ship
>>> leaves planet A for planet B and the length of the voyage is set for one
>>> year, usual for this commuter ship. The month of departure planet A is
>>> Mar 2010. The month of scheduled arrival planet B is Mar 2011. The ship
>>> leaves planet A on time (Mar 2010) and arrives planet B on time (Mar
>>> 2011).
>>
>> So you have a spaceship travelling at the speed of light. Just a tad
>> unrealistic.
>>
>
> I think you should lighten up a bit. Photons travel at c, and this is
> really just a special case of a more general question.
>
> The real problem is that looking at what happens at exactly c doesn't
> really show the general principle, which is why real world hypothetical
> spacecraft travel at 0.99c. But Mr Bradford maybe doesn't know that.
>
> I do agree however that his post seemed pointless.
>
> BTW, is you alias Inertial because of SR ?
>
>

======================

The same goes for you as "Inertial"

GLB

======================

From: G. L. Bradford on 11 Mar 2010 12:17

"Androcles" <Headmaster(a)Hogwarts.physics_v> wrote in message
news:nO3mn.243839$zD4.168230(a)newsfe19.ams2...
>
> "G. L. Bradford" <glbrad01(a)insightbb.com> wrote in message
> news:WaidncSioueeWwXWnZ2dnUVZ_sudnZ2d(a)insightbb.com...
>> Planet A and planet B are similar planets one light year apart. A ship
>> leaves planet A for planet B and the length of the voyage is set for one
>> year, usual for this commuter ship.
>
> So the ship travels at one light-year per year, unusual for any type of
> ship.

==================

Contraction and expansion of space-time. It did no such thing, though that
would seem the 'final' result. As I told Inertial, it did not come within
300,000 kps of the speed of light within its own frame. And though its own
clock measured a year for the voyage (Mar 2010-Mar 2011), the navigator
measured two years for the voyage (Mar 2009-Mar 2011) from the closest most
careful observations of the surrounding, enclosing, external universe at
large.

GLB

==================

From: Androcles on 11 Mar 2010 12:40

"G. L. Bradford" <glbrad01(a)insightbb.com> wrote in message
news:UqGdnRHFWJ4kuATWnZ2dnUVZ_omdnZ2d(a)insightbb.com...
>
> "Androcles" <Headmaster(a)Hogwarts.physics_v> wrote in message
> news:nO3mn.243839$zD4.168230(a)newsfe19.ams2...
>>
>> "G. L. Bradford" <glbrad01(a)insightbb.com> wrote in message
>> news:WaidncSioueeWwXWnZ2dnUVZ_sudnZ2d(a)insightbb.com...
>>> Planet A and planet B are similar planets one light year apart. A ship
>>> leaves planet A for planet B and the length of the voyage is set for one
>>> year, usual for this commuter ship.
>>
>> So the ship travels at one light-year per year, unusual for any type of
>> ship.
>
> ==================
>
> Contraction and expansion of space-time.

Bwhahahahahahaha! No such animal.

> It did no such thing, though that would seem the 'final' result. As I told
> Inertial, it did not come within 300,000 kps of the speed of light within
> its own frame.

Its speed is exactly zero in its own frame, the planets move in its
own frame.

> And though its own clock measured a year for the voyage (Mar 2010-Mar
> 2011),

Then the clock was broken or someone forgot to wind it.

> the navigator measured two years for the voyage (Mar 2009-Mar 2011) from
> the closest most careful observations of the surrounding, enclosing,
> external universe at large.

It's no good telling Inert anything, the cretin is dead from the neck up.

From: Ste on 11 Mar 2010 15:15

On 11 Mar, 15:12, PD <thedraperfam...(a)gmail.com> wrote:
> On Mar 11, 6:43 am, Ste <ste_ro...(a)hotmail.com> wrote:
>
>
>
>
>
> > On 11 Mar, 01:51, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
> > wrote:
>
> > > No, perhaps you didn't understand. As I say, this is *not* the twins
> > > paradox, because in the twins paradox only *one* twin leaves Earth.
>
> > > ________________________
> > > Its functionally the same. It is exactly the twins paradox, but with two
> > > twins apparently doing exactly the same thing.
>
> > > Even if you cannot see that, the explanation on the Wikipedia page of the
> > > Twins Paradox is trivially adapted for two twins.
>
> > > I assume that you do not understand the Wikipedia twins paradox page, or
> > > else you would know the answers to your questions already. Which parts don't
> > > you understand?
>
> > Let's just go through it step by step Peter, as we have been doing.
> > It's pointless spending 10 more postings arguing about how the
> > Wikipedia page does or does not answer the question, or how it is or
> > is not relevant. As I've just said in a post to Inertial, the only
> > analogy between my scenario and the twins paradox is that, in my
> > scenario, both twins leave Earth, and both return the same age as each
> > other - hence no paradox, and hence bearing no resemblance at all to
> > the twins paradox.
>
> First of all, let's establish what you think is paradoxical at all
> about the description of the twins in the twin puzzle. Then let's see
> whether this paradox is present in the case you mention.

As I understand it, the supposed "paradox" in the twins paradox was
that one returned younger than the other. It was, of course, not a
paradox at all, but that's besides the point.

In our scenario however, we have already agreed that both clocks
return to the origin displaying the same time, hence there is no
correspondence at all with the twins paradox.

From: PD on 11 Mar 2010 15:57

On Mar 11, 2:15 pm, Ste <ste_ro...(a)hotmail.com> wrote:
> On 11 Mar, 15:12, PD <thedraperfam...(a)gmail.com> wrote:
>
>
>
> > On Mar 11, 6:43 am, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > > On 11 Mar, 01:51, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
> > > wrote:
>
> > > > No, perhaps you didn't understand. As I say, this is *not* the twins
> > > > paradox, because in the twins paradox only *one* twin leaves Earth.
>
> > > > ________________________
> > > > Its functionally the same. It is exactly the twins paradox, but with two
> > > > twins apparently doing exactly the same thing.
>
> > > > Even if you cannot see that, the explanation on the Wikipedia page of the
> > > > Twins Paradox is trivially adapted for two twins.
>
> > > > I assume that you do not understand the Wikipedia twins paradox page, or
> > > > else you would know the answers to your questions already. Which parts don't
> > > > you understand?
>
> > > Let's just go through it step by step Peter, as we have been doing.
> > > It's pointless spending 10 more postings arguing about how the
> > > Wikipedia page does or does not answer the question, or how it is or
> > > is not relevant. As I've just said in a post to Inertial, the only
> > > analogy between my scenario and the twins paradox is that, in my
> > > scenario, both twins leave Earth, and both return the same age as each
> > > other - hence no paradox, and hence bearing no resemblance at all to
> > > the twins paradox.
>
> > First of all, let's establish what you think is paradoxical at all
> > about the description of the twins in the twin puzzle. Then let's see
> > whether this paradox is present in the case you mention.
>
> As I understand it, the supposed "paradox" in the twins paradox was
> that one returned younger than the other. It was, of course, not a
> paradox at all, but that's besides the point.

No, then you do not understand the paradox, because there is nothing
contradictory in that statement at all. It may be surprising, but it's
not contradictory, not paradoxical. Disagreement of clocks is not a
paradox.

The paradox, which is what is perceived (normally) by freshmen when
first introduced to this statement, is embodied in their immediate
classroom question: "But in the frame of the traveling twin, it is the
earth twin that is moving away and returning. Since this is symmetric
to the case of the traveling twin moving away and returning, then
shouldn't the traveling twin expect the earth twin to be younger when
they meet again?" Now perhaps the paradox is more apparent to you.

However, the puzzle is specifically designed to emphasize the danger
of oversimplifying. In fact, the two twins are NOT symmetric, because
one unambiguously experiences acceleration and the other unambiguously
experiences no acceleration. This then leads to a discussion of what
produces the asymmetry in the time.

Perhaps if you had started out by asking, "Since I don't see any
obvious paradox here at all, perhaps someone could illuminate me as to
why this is called the twin paradox?" Then at least you would have
been on square one.

> In our scenario however, we have already agreed that both clocks
> return to the origin displaying the same time, hence there is no
> correspondence at all with the twins paradox.