Elegant universe(the book)

[Zen Badger]

I have just started reading Brian Greenes "The Elegant Universe"

One part in particular I thought incorrect was his explanation of the time dilation effect in Relativity.

On page 38 he introduces the reader to a clock which consists of two mirrors facing each other.

A photon is then bounced between them in order to achieve the time intervals necessary.

A second, similar clock which is moving is then compared and the claim is made that the second clock is

recording a slower time because the timing photon has to travel further to complete its journey between

the plates.(Because it has to travel diagonally). Therefore Time has slowed down for the second clock.

He then adds a normal clock(rolex) to the moving photon clock and makes the astonishing claim that

the rolex mustslow down in order to avoid discrepancies between it and the photon clock.

I consider this to be wrong for several reasons and it does put me off reading the rest of the book.

Has anyone else read this book and what do they think?

[Darwinian]

I've not read it yet although it sits on my bookshelf, but, what are these reasons?

[Zen Badger]

@ Darwinian

Read the book from P38 then we can compare impressions.

[Darwinian]

It's a deal...

[theblindferrengi]

In reality the rolex would not speed up or slow down, but the time that it takes for the rolex to move would, it is a matter of the frame of reference from which it is percieved: If the viewer of the moving photon clock were moving with it, the photon would not be moving diagonally from that frame of reference, and from that perception time would not have slown.

In the book, this is a precursor to the idea that the speed of light is constant relative to the observer (the speed of light changes depending on how fast the observer travels, so the speed of light is really the speed of light plus the observer speed.)