Understanding Numerical Physics: Get Intuition & Memorize Constants?

[tim_lou]

It seems that understanding numbers in physics is often almost as important as understanding concepts, specifically when approximations to equations are made.

But I found myself lacking in intuitions in these numbers...

When my professor is lecturing, he always gives out numbers. for instance, kT for room temperature is about .026 eV (yes, he just remembers that) and rest mass of electron is about .51 MeV. From these numbers, my professor deduces how some approximations are valid. (When quantum mechanics can be applied, and/or a certain equation is valid)

It seems that I have a hard time grasping what those numbers really mean. I know it is a vague question but is there any way to get a better intuition out of numbers and/or numerical constants? Like when we say the mass of a proton is around 938 MeV, what does that tell us?

In addition, do most of you guys memorize important physics constants/numbers? like the constant G, h, k.. etc? in different units?

 

[mjsd]

well... the more use them.. and u will eventually remember them... like it or not
things like speed of light = 3x10^8 m/s, C=1.6x10^-19 and 0C=273K, pi=3.14159265358979323...
should be easy enough to remember

and no... I don't find them particularly intuitive either... they are just fundamental constants, not derived quantities after all

 

[arunma]

Personally I don't think it's that important to memorize all this stuff. I'm in grad school and just the other day when I had to numerically analyze a blazar energy spectrum, I completely forgot the value of h (and then another grad student commented that "you don't need to remember that crap" and photocopied his frequency to energy conversion cheat sheet for me). Oh sure, I remember some stuff, like the speed of light and the charge on an electron. But really, anything you can look up in a table, you don't need to remember. Even on exams you'll be given these values. And they don't aid your intuitive understanding of physics very much either. I couldn't remember kT for room temperature to save my life. It's more important that you understand the physical meaning of the equations you're using. For example, understanding the physical interpretation of the line integral of the magnetic field, and why it relates to current, is way more important than knowing the magnetic permeability of free space.

Just my opinion...

 

[robphy]

Some possibly interesting reading...
google.com/search?q=%22round+number+handbook+of+physics%22
google.com/search?q=order+of+magnitude+physics
google.com/search?q=fermi+question

http://link.aip.org/link/?AJPIAS/48/597/1
Man’s size in terms of fundamental constants. [American Journal of Physics 48, 597 (1980)]. William H. Press.

It's helpful to think in terms of [dimensionless] ratios of constants.

 

[Meir Achuz]

Try to use convenient units, so powers of 10 don't enter.
Don't work on memorizing. If you use a number often, it will come naturally.