(adsbygoogle = window.adsbygoogle || []).push({}); Still confusion in relativity of simultaneity and time dilation.....

Hello friend,

Still Something in my mind is saying that Relativity of simultaneity is the reason for time dilation even though i had some corrections in my understanding by posting various threads. Well,let me use Einstein's book Theory of Relativity to explain what i mean. I will not use any extra words or extra understandings.. Just i will explain the point by highlighting some important sentences..

Begins with chapter 8: On the Idea Of time In physics

In this paragraph that i quoted from the book,it gives the idea of time in physics.To explain this he said that clocks were kept at points A,B,C of the railway line and they are set in the manner that their pointers are simultaneously the same. From this condition,we were able to give 'time' of an event which is in immediate vicinity of event.As a result we will be able to record when every event happens. it is from this understandable that time is defined or measured with the help of events. Einstein said: ↑It is clear that this definition can be used to give an exact meaning not only to two events,

but to as many events as we care to choose, and independently of the positions of the scenes

of the events with respect to the body of reference 1) (here the railway embankment). We are

thus led also to a definition of " time " in physics. For this purpose we suppose that clocks

of identical construction are placed at the points A, B and C of the railway line (co-ordinate

system) and that they are set in such a manner that the positions of their pointers are

simultaneously (in the above sense) the same. Under these conditions we understand by the

" time " of an event the reading (position of the hands) of that one of these clocks which is

in the immediate vicinity (in space) of the event. In this manner a time-value is associated

with every event which is essentially capable of observation.

This stipulation contains a further physical hypothesis, the validity of which will hardly

be doubted without empirical evidence to the contrary. It has been assumed that all these

clocks go at the same rate if they are of identical construction. Stated more exactly: When

two clocks arranged at rest in different places of a reference-body are set in such a manner

that a particular position of the pointers of the one clock is simultaneous (in the above

sense) with the same position, of the pointers of the other clock, then identical " settings "

are always simultaneous (in the sense of the above definition).

then by giving this idea he said that in position of their pointers are simultaneous,then these clocks are of identical construction.And again if they are of identical construction,then these clocks go at thesame rate.And as the above quote used time as defined as events. so then whatever events that are simultaneous to a tick of a clock will be simultaneous to other clock,if clocks go at that same rate(from the above consideration)

This is an important line and i have got this as conclusion not from my own,i got it from the book.

Then let us go to the next chapter: The Relativity Of simultaneity

Now this paragraph says that clock go at different rates by used Relativity Of Simultaneity. In the example that is given by Einstein, Lightning was simultaneous with respect to embankment but not to train.Then Einstein immediately pointed out that Every Reference body has its own particular time and then said that there is no meaning of 'time' of event. Anyway we can understand that there is no meaning of 'time' of event from the above conclusion. But from the previous chapter we understood that time is defined by events. So the reference frames which sees events defined by same pointers of their clock go at the same rate. But in the case given in example, embankment reference frame needed only one tick of the clock to describe two events,while in train's reference frame needed two ticks of the clock to define those two events. So from the above consideration,These clocks should go at different rates!!! Einstein said: ↑Up to now our considerations have been referred to a particular body of reference, which

we have styled a " railway embankment." We suppose a very long train travelling along the

rails with the constant velocity v and in the direction indicated in Fig 1. People travelling in

this train will with a vantage view the train as a rigid reference-body (co-ordinate system);

they regard all events inreference to the train. Then every event which takes place along the line also takes place at

a particular point of the train. Also the definition of simultaneity can be given relative to the

train in exactly the same way as with respect to the embankment. As a natural consequence,

however, the following question arises :

Are two events (e.g. the two strokes of lightning A and B)

which are simultaneous with reference to the railway embankment

also simultaneous relatively to the train? We shall show directly

that the answer must be in the negative.

When we say that the lightning strokes A and B are simultaneous with respect to be

embankment, we mean: the rays of light emitted at the places A and B, where the lightning

occurs, meet each other at the mid-point M of the length A to B of the embankment. But the events A and B also correspond to positions A and B on the train. Let M1

be the midpoint of the distance A to B on the travelling train. Just when the flashes (as judged

from the embankment) of lightning occur, this point M1

naturally coincides with the point

M but it moves towards the right in the diagram with the velocity v of the train. If an

observer sitting in the position M1

in the train did not possess this velocity, then he would

remain permanently at M, and the light rays emitted by the flashes of lightning A and B

would reach him simultaneously, i.e. they would meet just where he is situated. Now in

reality (considered with reference to the railway embankment) he is hastening towards the

beam of light coming from B, whilst he is riding on ahead of the beam of light coming from

A. Hence the observer will see the beam of light emitted from B earlier than he will see that

emitted from A. Observers who take the railway train as their reference-body must therefore

come to the conclusion that the lightning flash B took place earlier than the lightning flash

A. We thus arrive at the important result:

Events which are simultaneous with reference to the

embankment are not simultaneous with respect to the train, and

vice versa (relativity of simultaneity). Every reference-body (coordinate system) has its own particular time ; unless we are told

the reference-body to which the statement of time refers, there is

no meaning in a statement of the time of an event

But when i said this in other thread,posters said that this directly lead to Relativity Of Simultaneity. Yes,They are right. But it does lead to the clocks going at different rates too.. But i haven't said about the other chapter...

Now through Lorentz transformation,we can understand that Time goes in different rates and it shows something more. Time dilates. Well, i think we cannot get this conclusion from dealing with relativity of simultaneity itself because i don't know what would happen if time beat faster than usual when moves..

This is the reason why i said that Relativity of simultaneity is related to time dilation...

Or relativity Of simultaneity causes Time dilation. Now we know that Lorentz transformation was derived from two postulates. that predicted time dilation. Well, Relativity of simultaneity requires these two postulates.

We can understand this from the chapter on idea of time in physics, The quoted word was written in footnotes of this chapter:

Well,these words conclusion is that These clocks should go at same rate.But we already described relationship between events and time. So since relativity of simultaneity is derived from these two postulates, time dilation too is and can be derived for these two postulates. Einstein said: ↑We suppose further, that, when three events A, B and C occur in different places in such a

manner that A is simultaneous with B and B is simultaneous with C (simultaneous in the

sense of the above definition), then the criterion for the simultaneity of the pair of events A,

C is also satisfied. This assumption is a physical hypothesis about the the of propagation of

light: it must certainly be fulfilled if we are to maintain the law of the constancy of the

velocity of light in vacuo.

Some General Doubts from the book:

In this quote why did he use the word "really"? Einstein said: ↑This diminished simplicity would be due to the fact that the carriage K would be in motion

(i.e."really")with respect to K0

What is the meaning of these lines? Einstein said: ↑We should expect, for instance, that the note emitted by an organpipe placed with its axis parallel to the direction of travel would be different from that

emitted if the axis of the pipe were placed perpendicular to this direction."

Here is the pdf of the book that i used here: http://www.marxists.org/reference/archive/einstein/works/1910s/relative/relativity.pdf

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Still confusion in relativity of simultaneity and time dilation .

Loading...

Similar Threads - Still confusion relativity | Date |
---|---|

I Black hole event horizon confusion | Mar 8, 2018 |

I Is the mass defect still considered with invariant mass? | Feb 8, 2017 |

B Relativily the apple can be still and the ground goes up? | Dec 7, 2016 |

I "relativistic mass" still a no-no? | Nov 11, 2016 |

I Standing completly still | Sep 3, 2016 |

**Physics Forums - The Fusion of Science and Community**