Why are there so many different symbols for scientific equations?

[Hawkingswnabe]

Does anyone have a link or some source for all of the scientific symbols used in equations like this one E=mc², I know that one doesn't really have any sybols in but I mean like the really long and complicated ones (((THIS IS NOT HOMEWORK!)))

 

[flatmaster]

You mean a list of physical constants? Wikipedia has an extensive list, but they're pretty much meaningless if you don't know what the mean.

http://en.wikipedia.org/wiki/Physical_constant

 

[diazona]

Does anyone have a link or some source for all of the scientific symbols used in equations like this one E=mc², I know that one doesn't really have any sybols in but I mean like the really long and complicated ones (((THIS IS NOT HOMEWORK!)))

If you're asking about what the various letters stand for - like E = energy, m = mass, c = speed of light - to be perfectly honest, it's just something you have to learn, because the meanings of the letters can change from problem to problem. For example, either U or V can stand for potential energy. If you're writing an equation that involves both potential energy and voltage (which is also V), you'd probably use U for the energy, but if you're writing an equation for a system of linked springs, you might use V for the energy.

However, even though most letters can have multiple meanings depending on the context, there are certain quantities that are always represented by a certain letter. For example, nobody writes the speed of light as anything other than c. Acceleration is nearly always a, except when it's the Earth's gravitational acceleration, which is normally written g. And so on. (There are, of course, a few exceptions like $\hbar$, where one symbol is only used to mean one thing and vice versa) The closest thing I know of to a "master list" of what symbols are used to represent various quantities is a table at the beginning of the CRC Handbook of Chemistry and Physics, but even that doesn't come close to including all quantities. There's no way you could ever make a complete master list, since people are defining new things that they need symbols for all the time.

I would offer this word of advice: the letters really aren't important, as long as you know what they mean. Don't get attached to particular letters meaning particular things. For example, knowing that Einstein's formula is written E = mc² isn't that important as long as you know that (energy) = (mass)(speed of light)². That way, if you read something where someone writes, "let U be the total energy" and then "U = mc²," you won't be confused. (Of course that's not the greatest example; nobody ever writes that particular formula with different letters, since it's so iconic. But that one's sort of a special case.)