07 July 2009

some thoughts on mass and energy

In Physics we teach students about both Conservation of Mass and Energy. Before we can do that, students have to understand what mass is. One of the ways I teach students about it is to describe mass as the inherent "laziness" of an object. In other words, the more mass an object has, the lazier the object is; the harder it is to get the object to change its motion (or lack of). I was thinking this morning that I may have to change the way I teach that.

I was listening to my mentor lecture about the mass of a Z boson which is right around 91Gev (giga-electron volts). Its a very massive particle and therefore very short lived. It decays to other particles within about 10^-25 seconds. That being said, you have to understand that when talking about particles, it doesn't matter if you are talking about energy or mass, they are measured in the same units because they are effectively the same thing. In high energy physics, scientists don't create matter from nothing. They collide particles with enormous kinetic energy (energy of motion) and that energy, coupled with the mass of the particles (usually protons or electrons) are converted into other particles.

So, if a particle has a lot of mass, (following my previous logic) it has a lot of laziness. However, following the logic of particle physics, if a particle has a lot of mass, it has a lot of energy. Therefore, using those two statements, something with a lot of energy is very lazy. Hmmm... yeah, I'm gonna have to change the way I teach mass, because that doesn't really make any sense, now. :-)

Thoughts? Comments?

Thanks for reading,


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