# Why is PI everywhere

1. Apr 4, 2012

### goldsax

we all know the PI crops up everywhere..

why for example would PI be found in the equation for the density parameter of the cosmological constant etc..
is there a book that can explain why PI rears its head up in all types os studies...

cheers

2. Apr 4, 2012

### genericusrnme

Anything that involves any kind of cirlcle, sphere or ball is going to involve pi, it crops up in densities and the likes because it's convenient to work with densities of 'balls' (especially if they are rotationally symmetrical!).
It's just like hbar in quantum mechanics, c in relativity and boltzmans k in thermodynamics (assuming we're not working in specialised units where certain constants are set = 1)
No pi = not working with cirlces, spheres etc
No hbar = classical limit
No c = non relativistic limit
No k = working at absolute zero

edit;
In regards to books, none that I know of will explicitely point this out but once you get use to the theories you'll start to see links between these physical constants and where they come from.

Last edited: Apr 4, 2012
3. Apr 4, 2012

### Hologram0110

@genericusrnme
Pi can also be the result of mathematics. Pretty much any function that involves sin/cos/tan ect is going to involve a Pi somewhere. This isn't surprising because how we define radians. It can also be found frequently when complex numbers come up (usually because of the relationship to geometric and exponential functions).

4. Apr 4, 2012

### genericusrnme

The trig functions and your e$^{ix}$ are still related to circles, namely the unit circle!

5. Apr 4, 2012

### goldsax

i will be doing maths as my next module..so will be further able to understand the concepts,
thanks for pointing the way...

6. Apr 4, 2012

### genericusrnme

No problem buddy