# Your vote for the most mysterious and wonderful of equations

1. Aug 22, 2008

### eratosthenes2

Figured this would bring interesting responses.

Mine is Newton's third law, only because of how it applies to rockets - the idea that some gun/rocket accelerates forward exactly based on the speed and mass of the bullets/exhaust is pretty weird when u think about it. That's something moving forward exactly at the rate of stuff moving backward. Seems odd.

2. Aug 22, 2008

### tiny-tim

e = -1

3. Aug 22, 2008

### nicksauce

$$i^i = e^{\frac{-\pi}{2}}$$ (The principal value of it anyway)

4. Aug 22, 2008

### Redbelly98

Staff Emeritus
C'mon folks, this is a physics thread :grumpy:

I vote for Schrodinger's Equation.

5. Aug 22, 2008

### nicksauce

Physics-wise, I would vote for the least action principle.

6. Aug 24, 2008

### Constructe

The strangest is String theory, especially since it proposes nothing new except there should be a graviton... How is that different than particle physics? As for the rest of the goop, you can't even test for it. Oh... well a sparticle may show up. But once again, others also proposed super heavy particles. So that also proves nothing. 11 degrees of freedom. Gee if you are bored maybe you can make some theory with 297 invisible dimensions that explains why a cat has whiskers.

7. Aug 24, 2008

### tiny-tim

me bored when i can constantly ponder the mysteries of the bowliverse? :rofl:

my theory is that whiskers have cats …

the cat is merely whiskers' way of producing more whiskers!

8. Aug 24, 2008

### rbj

that's the one that first came to my mind, except i was thinking in this form:

$$e^{i \pi} + 1 = 0$$

that relates the five most prominent pure numbers together in one equation.

the Multiplicative Identity operator
the Imaginary unit
the base of natural logarithms
and pi.

9. Aug 25, 2008

### Crosson

If f(x) is an infinitely many times differentiable function, then:

$$e^{\frac{d}{dx}} f(x) = f(x + 1)$$

10. Aug 25, 2008

### jackiefrost

euler+gauss+reimann=infinity

11. Aug 25, 2008

### pallidin

My vote is for equations involving pi. I've always been fascinated by the 3.14... relationship.

12. Aug 25, 2008

### gel

nah, that's just a boring identity. What does it have to say about anything?
Besides, this is a physics thread.

After a bit of thought, I suggest the following

$$\frac{dQ}{dt}\ge 0$$

i.e., the second law of thermodynamics. Total entropy of a closed system can only increase over time.

It's certainly mysterious. It doesn't appear in the fundamental laws of physics, at the lowest level, but must be a consequence of them. It seems like you should be able to get around it (e.g. Maxwell's demon) but there's always a catch, and the second law always holds. It's also very important and rules all of our lives.

13. Aug 28, 2008

### sp1408

not really,S=k*ln(w),I just cant understand how they can define the amount of disorder in a system....

14. Aug 28, 2008

### Andy Resnick

I vote for Euler's first law:

$$\frac{d}{dt}\int \textbf{v} dm = \textbf{f}$$

Because it covers all of continuum mechanics, including dividing surfaces.

15. Aug 28, 2008

### uart

Hey Crosson, what is the definition of $$e^{\frac{d}{dx}}$$ ?

Am I right to assume it's the operator :

$$[1 + \frac{d}{dx} + \frac{1}{2!} \, \frac{d^2}{dx^2} + ....]$$.

Or does it mean something else?

16. Aug 28, 2008

### Topher925

$$\frac{Sin x}{n}$$ = 6

+10 cool points for anyone that figures that out.

17. Aug 28, 2008

### tiny-tim

Easy!

special case of …

$$\frac{Sin^m x}{n^m}\ =\ 6$$

18. Aug 28, 2008

### Topher925

NO! But nice try though. :tongue:

EDT: Ok, Tim figured it out. Hes now 10 points cooler.

Last edited: Aug 28, 2008
19. Aug 28, 2008

### gel

that's the mystery part

20. Aug 28, 2008