[Jacaranda]: Relativity of Simultaneity (1 Viewer)

[Mustafa Jihad]

Can someone explain to me the whole train scenario shown on page 74 of Jacaranda. I don't get how the observer outside the train sees the two doors opening at different times. Shouldnt the light inside the train travel towards the two doors at the same time anyways regardless of which observer is looking?

Paragraph 2 of Page 74 is very confusing. It says that for the outside observer, the backdoor should open before the front door because the light inside the train reaches the backdoor before the front door. But what I dont get is, if this is the case why should the light travelling towards the front door even reach it at all? Isnt it travelling at the same speed as the train, and hasnt the train moved on already? How could it possibly reach the front door if they are travelling at the same speed?

All this may not seem to make sense, maybe because I just dont get it, so could someone please straighten this out for me.

 

[alcalder]

Mustafa, I'm trying to figure out how the picture in Jacaranda works. It seems screwy to me. Have a look at this website. It make smore sense here.

http://www.bun.kyoto-u.ac.jp/~suchii/Einstein/rel.TS.html

The flashes are outside the trains and simultaneous. So, to the outside observer, they appear at the same time. BUT for the person inside the train, they are moving forward and reach the front flash before they back flash reaches them, so they see the front flash first and then the back flash.

The only thing I can think of with the Jacaranda picture is:

The lamp is moving at the speed of the train and so the light travels with the speed of light plus the speed of the train (which we know does not happen in real life). So, the person on the train sees both doors open at the same time. However, the person off the train is not moving. The train is moving away from him. The back door is closer and so he sees that open first and then the front door open.

The website explanation is a lot better.

 

[rama_v]

As a side note, here is an excellent site that may help all those learning relativity

http://www.phys.unsw.edu.au/einsteinlight/