On Mon, Dec 24, 2018 at 4:24 PM Bruce Kellett <[email protected]> wrote:
> On Tue, Dec 25, 2018 at 4:59 AM Jason Resch <[email protected]> wrote: > >> On Mon, Dec 24, 2018 at 12:30 AM Bruce Kellett <[email protected]> >> wrote: >> >>> On Mon, Dec 24, 2018 at 4:03 PM Jason Resch <[email protected]> >>> wrote: >>> >>>> On Sun, Dec 23, 2018 at 11:06 PM Brent Meeker <[email protected]> >>>> wrote: >>>> >>>>> On 12/23/2018 7:17 PM, Jason Resch wrote: >>>>> > >>>>> > How can this be? The rocket is a rigid structure, the front and rear >>>>> > clocks accelerate at the same rate. >>>>> >>>>> First, there are no rigid objects in relativity theory. Otherwise >>>>> they >>>>> could be used for FTL signaling. Second, there is no simultaneity at >>>>> different places, like the front and rear of the rocket. So it is >>>>> frame >>>>> dependent whether the two ends of the rocket begin to accelerate at >>>>> the >>>>> same time. >>>>> >>>>> >>>> The level of clock desynchronization is proportional to the speed and >>>> the length of the rocket. That it is one rocket doesn't even matter, it >>>> could be two rockets, which both separately accelerate at the same time >>>> given by a signal initiated from immediately between them. This is just >>>> showing that length contraction is only a spatial length contraction. The >>>> length through space time is constant, but when moving through space, an >>>> object's length will partially extend through space and partially extend >>>> through time. To the extent that an object's length contracts you will see >>>> a corresponding increase in the reach through time. (this is unrelated to >>>> acceleration effects, or rigidness). >>>> >>>> If it were related to rigidness, then the effect would disappear with >>>> the two separate rockets, but it doesn't. Similarly, if it were related to >>>> acceleration rates, rather than absolute velocity, it would be unrelated to >>>> the distance separating the clocks but it's not. Here is an example of >>>> what I am talking about, just to be clear. >>>> >>>> If a 100 meter rocket accelerates to 80% of c, then it will length >>>> contract to 60 meters, but will also extend 80 meters through the dimension >>>> of time. The total length remains 100 meters (0.6^2 + 0.8^2 = 1). >>>> However, clocks that were initially synchronized between the fore and aft >>>> parts of the rocket are separated by (80 meters / c) = 266.85 nanoseconds. >>>> If you take the clock from the front to the back you will see it speed up >>>> and resynchronize with the clock in the back when brought into proximity >>>> with the clock in the rear, likewise if you bring the clock from the rear >>>> towards the front it will slow until it resynchronizes with the clock in >>>> the front by the time it is brought into proximity with it. You are >>>> carrying the clock through the time dimension as you move it towards the >>>> front or back of the ship. >>>> >>> >>> I don't understand this. If the two clocks are moving at the same >>> velocity there is no difference in clock rate between them. That's why I >>> thought you were talking about the acceleration phase -- clock rates can >>> differ then, but if the two clocks are at either end of the rocket moving >>> inertially, and at rest wrt each other, then their rates are the same, >>> regardless of the distance apart. >>> >>> >> As seen by someone who perceives the rocket to be length contracted, the >> clocks will not appear to be in sync. >> > > That is factually wrong. The special relativistic apparent change in clock > rates depends only on the relative motion, so from the point of view of > someone at rest on the ground, the clocks at the front and rear of the > coasting rocket will be travelling at the same velocity relative to him. So > they will both appear to be going either faster or slower at exactly the > same rate, depending on the direction of the relative motion. > Then what is the meaning of this problem on page 42: https://www.relativity.li/uploads/pdf/English/Epstein_en.pdf Two rockets fly past each other at 0.6 • c. A measures the length of the other rocket B to be 40 m. What is the rest length of the rocket B, and how much are the clocks at the tip and at the end of rocket B for A desynchronized, given that they are synchronized for B? And which of the two clocks is running fast for A? More details: http://galileoandeinstein.physics.virginia.edu/lectures/synchronizing.html Jason > > I think you have been totally confused by your ideas about everything > going at a constant speed through either space or time. I thought you had a > basic confusion when you appended those rather silly diagrams a post or so > ago. You have to go back to the basic equations of the Lorentz > transformation to get these things straight. > > Bruce > > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
