Sorry Mr. Egdall, Congratulations Dr. Tom Swanson

[Nicholas Kang]

This post is dedicated to Mr.Egdall and Dr. Tom Swanson but others can post or reply too.

Mr.Egdall

 

I bought your book Einstein`s Relatively Simple a few months ago. I enjoy reading your book at first. It is quite humorous and the examples given are quite compelling, rigid and vivid. My knowledge have increased much ever since I started to read your book. But soon it start to fall out of stage. The book is still very new. The datas are updated but the mathematics, to me are too simple. And the mathematics are not stated clearly in the end-the appendix section. Here is an example:

 

In appendix A, your time dilation and length contraction formulae derived from Lorentz Transform are

 

delta x prime= delta x/F(simplified)

delta t prime= delta t/F(simplified)

 

The formulae relates reference frame S and S prime.

 

However, I soon found out that if I rearrange the formulae

(I will not write delta anymore)

 

x` = x/F

If F=0.5 ,then x=x` times 0.5

if x is 3 cm, then x` is 6cm. You are 6 cm and the observer in S` frame observe you as 3 cm. (For length contraction, for example)

 

But what if I observe the second observer? Should I still use your(the above) formula?

If I do, then it won`t work because in the end, I express x as the subject but not x`

I checked wikipedia then only I know I must use positive rather than negetive for the not yet simplified formula.

 

The actual formula is (for length contraction and x as the spatial dimension)

Lorentz Transform first formula

x prime = (x-v delta t)/F, where F is Lorentz Factor square root 1-(v/c)²

t=0

 

x prime =x/F

 

to find the opposite, x=(x prime + v delta t)/F

Change the negative sign to positive and the formula works for the opposite. However, it is not mentioned in the book. I desperately tried working the formula for months yet I only get to know it from wikipedia. (I am not blaming Mr.Egdall but advising him to do better in the future) Please don`t feel angry or irritated. I apologised if I hurted you.

 

Also, in most technical papers, gamma factor or the reciprocal form of Lorentz factor is used. In the beginning of the book, I used to see the word the reciprocal in tables describing examples of the speed of rockets for Crash and his partner. Initially, I have no idea of why reciprocal because there is no sign of reciprocal used in the mathematics described in the appendix. Only later when I checked wikipedia, it comes to me.

 

The book is good and examples are very humorous. But there are still lots of works to be done. The backcover of the book states that "If you only read one book on special and general relativity, this is the one to read." This can be quite misleading because it is very useful to first-time-learners but soon you find the mathematics very incomplete and it can`t really be the only book. Further reading must be done.

 

Dr. Tom Swanson

And also congratulations Dr. Tom Swanson because your name appear on one of Egdall`s Notes with Sources Section. Your replies in SFN has been adopted and acknowledged by Mr. Egdall.

 

I am supporting you, Mr. Egdall. I like your humourous way of describing relativity. I hope you can do even better in your upcoming book. Maybe Quantum Mechanics?

 

Finally, can your book be cheaper next time, it costs something like 62 ringgit 50 cent in Malaysia. 1 USD is equivalent to around 3 ringgit.

 

Thanks.

Edited October 16, 2014 by Nicholas Kang

[StringJunky]

FYI it's Dr Tom Swanson. He puts his first name initial (t) on the end of his username.

[Nicholas Kang]

I would like to express my deep apology to Dr. Tom Swanson for not respecting him when calling him. I would like to thank Mr. StringJunky for advising me Dr. Tom Swanson`s real name.

 

Sorry, Dr. I should have researched deeply about your name before postring this topic. it was my fault for not respecting you, Dr.

Learning is part of a teenager`s life.

 

Thank you Mr. StringJunky. Sorry, Dr. Tom Sawnson.

[swansont]

No offense taken; apology accepted.

[Phi for All]

FYI it's Dr Tom Swanson. He puts his first name initial (t) on the end of his username.

 

Navy training. Swanson, T is how he had to fill out five years worth of forms..

[swansont]

 

Navy training. Swanson, T is how he had to fill out five years worth of forms..

 

Forms, five years' worth, SIR! In triplicate!

[Phi for All]

 

Forms, five years' worth, SIR! In triplicate!

 

Ah, that explains the enhanced forearm muscles.

 

[StringJunky]

Phi for All, on 16 Oct 2014 - 1:52 PM, said:

 

Navy training. Swanson, T is how he had to fill out five years worth of forms..

Yes, that makes sense.