Re: THE RELATIVITY OF THE LENGTH

On Dec 6, 11:50 pm, "Dirk Van de moortel" <dirkvandemoor...@ThankS-NO-
SperM.hotmail.com> wrote:
"Stamenin" <task...@xxxxxxxxxxx> wrote in messagenews:c9992b46-58ed-416f-95ed-3370c5e87aab@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Dec 6, 2:53 pm, "Dirk Van de moortel" <dirkvandemoor...@ThankS-NO-
SperM.hotmail.com> wrote:
"Stamenin" <task...@xxxxxxxxxxx> wrote in messagenews:21211e4c-0606-4d34-b00f-367701a4b9ff@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
WHY THE LENGTH IS SHORTENING IN EINSTEIN RELATIVITY?

This question is very often reopened in many discussions, and still is
not clarified. In fact the answer is that according to LT the length
increases in a relative motion with constant speed and in a straight
line. Here is the explanation:
If the LT for length is:
x=(vt'+x')/R
For two systems of coordinates K attached to the earth an K' attached
to a train then for a distance of 1m in the train we should have:
x'2-x'1=1m.
The corresponding distance at the earth should be:
x2-x1=(x'2-x'1)/R=1m/R. Where R=[1-(v/c)^2]^0,5.
So because (R<1) the length calculated with the LT becomes bigger for
the observer situated on the earth.

(made a typo in my previous reply - please discard)

If K' is attached to the train, then you must make sure that
in the K-system, you measure the endpoints of the train at
the same time, so t1 = t2

Generally this condition isn't necessary.

Of course it is necessary.
If you measure the length of a moving train, you have to find
the distances to the rear and the front at the same time, and
then you can culculate the difference between these distances
to find the length.
Would *you* measure the distance to the front now and the
distance to the rear 15 minutes later?

Dirk Vdm- Hide quoted text -

- Show quoted text -

I like to give an answer to all participant in this discution. I am
very surprised that puting the condition t1=t2 you put in evidence
that you do not know how could be applied an mathematical relation.
When we use a relation like the LT for distance, we have to put the
known conditions in the right site of the relation end by computing
obtain the result in the left site. So is logic to put the condition
t2'=t1' for the system K' to know that the difference x2'-x1'=1m is
taken in the same time. If you know the length in the system K than
you can use the inverse relation x'=(x-vt)/R and can calculate what
gives the LT for an observer in the train. And just in this case you
obtain an increasing of the length. Your arguments don't show nothing
else but that you have learnt something wrong and continue to defend
it witout any personal judgement. So I ask you how is possible to have
for v=c length of zero and mass of infinite for that rod? Object that
doesn't exist and has a mass of infinite!!! Are you serious?
.

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