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Add your guestbook entry by clicking here. This is a guestbook; if you have a question or a problem, email me at christoph@motionmountain.net instead. For suggestions or errata, please use the wiki at https://sites.google.com/site/motionmountainsuggestions/.

There are 405 entries on 41 pages.
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Energy Universe

June 26, 2015

Author:       Atlas Delete  Reply  IP  
http://research.zonebg.com/en/books.htm
Energy is every DIFFERENCE in time - space according to time - space itself.

CS: Dear Sir, the statement you make is either nonsense or false.

Great read.

June 3, 2015

Author:       C. Sarge Delete  Reply  IP  
I really appreciate this overview of physics, but I just have one question. Why such an anti-Newton bias? He is widely regarded as the greatest scientist of all time, but you seem to regard him as almost inconsequential. Does history regard him to highly?

CS: I do not know anybody who thinks that Newton is the greatest scientist of all time. Such fairytales are only told by bad teachers. (What does "greatest" means anyway?) On the other hand, he surely was one of the most important alchemist of all times. He spent a much larger part of his life doing alchemy than doing physics. Is alchemy science? He spent most of his life looking for the philosopher's stone. Is that what you call the greatest scientist of all times? Also theology was more important to him than physics. Of course everybody is free to believe anything. But Newton is not a myth or a fairytale, he was a real person. The book tries to give a fairly objective account of him.

Nice SR book (but...)

May 6, 2015

Author:       Pete Brown Delete  Reply  IP  
I took a look through the relativity text and found it to be a very nice text. There's one mistake in it that people make all too often and that's the belief that Einstein never used or believed in using relativistic mass (RM). This is incorrect. RM, m, is defined as momentum, p, over speed, v. I.e. m = p/v. If the object is a particle which moves slower than light then the RM can be written as m = gamma*m_0 where m_0 is the particles proper mass. If the particle is moving in a gravitational field and is moving slowly then m does not equal m_0. m is a function of the gravitational potential. This can be found in Moller's text. I've derived it and placed it on my website at: http://home.comcast.net/~peter.m.brown/gr/uniform_force.htm

Einstein used this in his text "The Meaning of Relativity" on page 102.

In his GR paper of 1916 he wrote that mass and energy are essentially the same thing and is fully described by the "energy tensor" which we now refer to as the "stress-energy-momentum tensor". He also assigned a mass density to EM energy density in one of his papers. So asserting that he never used RM is quite misleading. Actually he had to depend on it in his argument regarding Mach's principle.
Einstein also

CS: Dear Pete, in the book you mention, Einstein uses m to mean "rest mass", what you call m_0 ! In fact, he always did so, as far as I know. There is no paper where he used both m_0 for rest mass and m for relativistic mass. Also in the book you cite, Einstein does not use "relativistic mass" at all. And on page 102, there is nothing of what you are claiming. Furthermore, in the 1916 paper you mention, Einstein just says in §16 that "träge Masse nichts anderes ist als Energie", but not that relativistic mass makes sense or should be used. Finally, also your statement on Mach's principle is mistaken. You are distorting facts. And m does not depend on the gravitational potential, whatever you may mean by "m". This latter statement is positively false. The truth is: "Relativistic mass" was never used by Einstein; it is a concept only used by tabloids and by bad books.

A great idea- free physics

January 2, 2015

Author:       Tomctutor Delete  Reply  IP  
It's so refreshing to see this textbook provided free of charge for the whole student community worldwide as such traditional paperbooks in physics are typically very expensive, with some undergraduate volumes near $200 each to purchase.
The author will definitely have a place on my website here in Scotland. Thankyou Christoph

CS: Tom, thank you! The book is written both for enjoyment and learning.

Physics

November 15, 2014

Author:       Michael Dube Delete  Reply  IP  
Dear Christoph
Physics was a mystery to me in high school. It was intimidating; a struggle to get through. Over the last 40 years I continued to take a poke at understanding at least the basics. Now I find MotionMountain Physics - and understanding increases with every page. Thank you for this wonderful work. Students will be better for it; I know I am!

CS: Thank you for your message - I am happy that you like the book! If you have questions, email me.

October 11, 2014

Author:       Oliver Delete  Reply  IP  
Your work gives an new and unique perspective of Physics. Motion Mountain is my favourite among the hundreds of Physics ebooks I've explored. It's awesome, thank you!

CS: Thank you - enjoy it!

Awesome Job !!

August 15, 2014

Author:       Amarnath Delete  Reply  IP  
I shall go thru the book and let you know my honest thoughts about this book. Downloading now.

Good Work. RESPECT TO YOU :)

CS: Above all, enjoy it!

July 23, 2014

Author:       Michele Raccio Delete  Reply  IP  
Thank you so much for this wonderful cultural adventure!

CS: Thank you, and enjoy it!

Bucket filled with water

June 16, 2014

Author:       Martin Delete  Reply  IP  
Hi, I tried very hard, to get behind the challenge 4 in the first book. My bucket always hangs vertically and I can't understand why it shouldn't do that with an certain amount of water? It rankles me to stuck with one of the first challenges.

CS: Try it with a bucket at home. Tip: it works best with a light (plastic) bucket!

Motion Mountain

May 16, 2014

Author:       Tessa Delete  Reply  IP  
Thank you VERY MUCH

CS: Thank you for your message!

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