Sixty Symbols

The site of the University of Nottingham  has a nifty front page full of physics symbols each linking up to a YouTube video. The videos are quite easy to take on and understand. For example the video below is the result of clicking on E=mc2; one of the more popular videos.
What may interest most physics-philes is that in this particular video, the term E=mc2 is actually not a complete description of the concept itself. We physicists appreciate that the m in this term is the rest mass or relativistic mass but the complete more correct expression is:
E2= p2c2 +m2c4
Why is this important? The term:
E = mc2
states the equivalence of energy and mass and when particles bind together, they must do so with a binding energy E. For example take the constituents particles of an atom where all their masses sum to M1. Putting them together to form that atom requires energy so some of M1 is converted to energy leaving an atom with a total mass M2 and with the same internal constituent particles. How cool is that!
I don’t want to just parrot the video, but I will say it is beautifully and simply explained as to how Dirac got hint of the positron by coming up with the simple negative energy roots of the complete expression. The positron was discovered later.
Each video is a layman’s dream spiel on an important concept in our understanding of the universe. So many of the ideas we hear about when physicists discuss the Standard Model, Quantum Mechanics, etc. seem abstruse and disjointed. How can they come together to make a coherent picture of what we think may be happening? One may get a somewhat more coherent picture by viewing everything historically rather than all at once. It worked for me



About Deborah Leddon

Vegetarian Mother and Wife, Scientist at UTD CSS, passionate about my family, animal rights, the outdoors and my violin.
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