How to distinguish left vs right

[Phybie]

Hi All,
This is a question that has been bugging me for a few years now. How can we tell left vs right without using something else as reference? The same applies for clockwise vs anti-clockwise.
For example, the way I can tell left and right is by relating to my body. If I was a point particle, how do I tell left vs right and clockwise vs counter-clockwise?
Particles have the concepts of chirality and helicity (which I don't understand by the way) that seem to be related to knowing left vs right. How do they "know"? Similarly, how does the magnetic field "know" which way to align based on the direction of the electric current?

Can anyone shed some light on this? Any comments are much appreciated.

 

[Sefrez]

Well certainly if you were a particle, you would have to reference off something to be in a clockwise or counter clockwise motion. Or that is, there must be some reason for this induced motion. So I don't think of it so much as knowing but rather it is simply reacting with its environment. We can then describe the particle with a clockwise or counter clockwise motion, which is definitely relative to you (look from the other side it will be the reverse.) Of course, then, this only has meaning when we can interpret it and build from it in a consistent way.

 

[Khashishi]

That's a good question. There is no difference between right and left other than the point of view. And clockwise becomes counterclockwise depending on if you look at the front or the back. Helicity is whether it is spinning clockwise or counterclockwise in the direction it is moving, so it depends on the observer. On the other hand, chirality is the difference between your right hand and your left hand. You can't transform one into the other, no matter which way you observe, without doing some mirror flip, which an observer can't do. An observer can look forward or back or move in whichever direction, but it can't mirror itself.

Also, the right hand rule is purely a convention. The direction of the magnetic field and spin are based on this convention, but there is no physical meaning to it. We could use a left handed system if we were consistent about it. It's merely a bookkeeping system. You should not think of the "z" component of the spin or magnetic field as having anything to do with the "z" direction, but rather having everything to do with the xy plane. Similarly, "y" is actually referring to the xz plane and x is referring to the yz plane. There are actually 3 components to the magnetic field: yz, xz, xy. Physicists have just found it convenient to relabel these to -x,y,-z. Same deal with angular momentum.

A more correct and symmetric way of handling the direction of the magnetic field is by using the electromagnetic tensor, which has 6 components, in which the electric field is given by the xx, yy, and zz components and the magnetic field is given by the -yz, xz, -xy components.

 

[skeptic2]

I believe Richard Feyman answers this question in Surely You're Joking Mr. Feynman.

 

[pmacias]

I can provide some insights into how we distinguish left vs right and clockwise vs anti-clockwise in the world of particles and physics. First, let's define what we mean by left and right. In physics, left and right are considered to be opposite directions, with left being defined as the direction of rotation that is counterclockwise when facing towards the rotation, and right being the direction of rotation that is clockwise when facing towards the rotation. This definition is based on the right-hand rule, which is commonly used in physics to determine the direction of a magnetic field and the direction of a current-carrying wire.

Now, how do particles "know" left vs right? This is where the concepts of chirality and helicity come into play. Chirality refers to the property of a particle or object that cannot be superimposed onto its mirror image. This means that a particle's chirality determines its handedness, or whether it is left-handed or right-handed. Helicity, on the other hand, refers to the direction of a particle's spin relative to its direction of motion. In other words, it is the projection of a particle's spin onto its momentum.

So, how do particles determine their chirality and helicity? This is largely determined by the interactions between particles and the fundamental forces of nature. In the Standard Model of particle physics, the weak force is responsible for the creation of chirality in particles. This is because the weak force interacts differently with left-handed and right-handed particles, leading to a preference for one over the other. As for helicity, it is determined by a particle's intrinsic properties and is not affected by external forces.

Now, let's address the question of how the magnetic field "knows" which way to align based on the direction of the electric current. This is due to the interaction between the magnetic field and the moving charges within the current. The right-hand rule comes into play here as well, as it determines the direction of the magnetic field based on the direction of the current. Essentially, the magnetic field is created by the flow of charged particles, and the direction of this flow determines the direction of the magnetic field.

In conclusion, the concepts of chirality and helicity play a crucial role in distinguishing left vs right and clockwise vs anti-clockwise in the world of particles and physics. These concepts are determined by the interactions between particles and the fundamental forces of nature. And when it comes to