# Why is clockwise clockwise?

1. Feb 11, 2008

### prof tipesh

Why is clockwise clockwise, and not the other way round?

Prof Tipesh cannot see the problem - either clockwise is clockwise or it isn't, but he is not wise, he is otherwise.

Prof Tipesh says he knows up from down by dropping stones, forward from backward by walking, left from right from his hands, and clockwise from counterclockwise from clocks.

The last two seem like tautologies. But biologically, we come in right and left versions, but I've never heard anyone say, well, I'm naturally counterclockwise, but they forced me to be clockwise when I was a child. So the last is a tautology. Or is it?

2. Feb 11, 2008

### CompuChip

Clockwise is clockwise because clocks always go clockwise. The reason for that has something to do with sundials, also see this page.

Quite logical actually, but interesting nonetheless.

3. Feb 11, 2008

### Ulysees

Another thing is that some laws of physics apply only clockwise, eg the Biot-Savart law, which means there is something fundamental in the universe about clockwise-ness.

-wiseness may be a characteristic of Eucledian space, not of the universe. But I don't really know about other spaces so I stop here.

Last edited: Feb 11, 2008
4. Feb 11, 2008

### CompuChip

Is there? We have defined the outer product in such a way that the Biot-Savart law reads
$$d\mathbf{B} = \frac{\mu_0}{4\pi} \frac{I d\mathbf{l} \times \mathbf{r}}{r^3}$$
But why is that more fundamental than having
$$d\mathbf{B} = \frac{\mu_0}{4\pi} \frac{I \mathbf{r} \times d\mathbf{l}}{r^3}$$
where the direction can be found by a left-handed cross product (e.g. $\mathbf{y} \times \mathbf{x} = \mathbf{z}$)?

5. Feb 11, 2008

### prof tipesh

Gee, life was more challenging before wiki! I was born in the Southern Hemisphere, and when I was 7, I decided to make a sundial, and I followed all the instructions right, and yet it went the wrong way! After about 4 hours of puzzling about what I did wrong, I understood!

Turn a clock around, and it runs counterclockwise, so while there is indeed an oppositeness between clock and counter, there is nothing fundamental about one or the other. It is a matter of perspective.

So if sundials had been invented below the equator, clockwise would be the other way round.

6. Feb 11, 2008

### Ulysees

Alright, then let's correct it to this:

Whichever of the two ways you write the law, the universe prefers one of the two directions for the B-field, it knows which way to point the magnetic field vector.

Then you might say, "and what is the magnetic field, its direction could have been defined from south pole to north pole instead of north to south." True, it could have. Ultimately it's the force it generates that matters. The force on a moving charge. And the universe... knows which direction to point the force to.

Last edited: Feb 11, 2008
7. Feb 11, 2008

### prof tipesh

Sorry, another correction. The Field is our construct. We can indeed use LHR (left hand rule) for the field as well. The force on a moving charge does seem to be the real thing.

In GR gravitational force is eliminated by local curvature, but that local curvature is always positive, so all masses move the same direction. EM in flatspace does indeed seem to be a real force, one way if you're positive, the other way if you're negative, and straight down the pike if you're electrically neutral.

I bet one day some wiseguy will eliminate this force too! However, that changes nothing here. Objects know which way to go!

8. Feb 11, 2008

### Ulysees

Might get a little too philosophical here, but since you seem to know enough physics to understand, here you go:

Mathematical models like Newton's law of gravity are never the real thing, they are human constructs of limited range of applicability and limited match with "reality". For example you can't use Newtonian physics with very fast moving objects, not to mention that gravitational motion can be accounted for by distorting space instead. But that does not invalidate Newton. It just reminds us that mathematical models have limited range of validity.

Likewise relativity is not enough with very small objects, we need radically new mind models and equations at this scale. But that does not mean relativity is wrong, it is just limited in its range of applicability, as is every theory and mathematical model.

Quantum equations and mind constructs, I am sure are limited too, sooner or later we will need new models for something else, eg extrasensory perception.

So what is real and what isn't? Ultimately it doesn't matter. What matters is that we have a good enough mind construct for a given situation.

Will we ever have an all-inclusive mind model for everything in physics? Some people here think we already have answers for everything... 100 years ago, before relativity and quantum physics and all that, I bet you 100 years ago physics conversations had pretty much the same flavour of know-it-all as now. It's human nature, a human dillusion that's not easy to overcome.