Why Are Human Hands Considered Chiral?

[jd12345]

How are our hands chiral??

How are human hands chiral at all. Put them in the praying position and they are superimposable!
"The left hand is a non-superposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands to coincide" says wikipedia.
Some of my teachers and friends say you cannot rotate them like that but clearly we can orient them in any way we want so in the praying posiiton when palm faces palm hands are superimposed
I don't understand this at all - why are hands referred to as chiral at all?

 

[horsecandy911]

Hi jd12345,

I think you're misunderstanding the word "superimposable". This means that the outlines of the hands should be able to match up exactly-- i.e. one hand can occupy exactly the same space as the other hand. One way to see this is to think of a left-handed glove. This glove delineates a region of space that the left hand can occupy, but the right hand cannot. No matter how we rotate a disembodied right hand, it will never fit snugly into a left-handed glove. Because it can't occupy the same region of space as the left, it is not superimposable with the left.

In the praying position, one face of each hand is indeed matching up along the same outline, but the whole hands are not. So this does not demonstrate superimposability.

 

[atyy]

Make your left-hand curl one direction (let's define that as clockwise) and give a thumbs up. In order for your right hand to curl clockwise, it must give a thumbs down.

 

[jd12345]

got it , thank you

 

[LudusRex]

Dear reader,

Thank you for your inquiry about the chiral nature of human hands. I am happy to provide an explanation.

Chirality is a concept used to describe objects that cannot be superimposed on their mirror images. In simpler terms, this means that the object and its mirror image are not identical and cannot be made to overlap perfectly. This property is found in many objects in nature, including human hands.

Our hands are chiral because they have a specific arrangement of bones, muscles, and tendons that cannot be mirrored exactly. This is most noticeable when we compare our left and right hands. No matter how we orient them, they will never be identical.

For example, if we hold our hands in the praying position, the palms will be facing each other, and it may appear that they are superimposable. However, upon closer inspection, we can see that the thumbs are on opposite sides and the fingers are in opposite directions. This makes it impossible for all the major features of both hands to coincide.

Some people may argue that hands are not chiral because they can be rotated to overlap in certain positions, such as the praying position. However, this is only possible because our hands have a certain level of symmetry. If we were to compare our hands to a truly chiral object, such as a spiral staircase, it would be clear that our hands are indeed chiral.

In conclusion, human hands are chiral because they have a specific arrangement of bones, muscles, and tendons that cannot be mirrored exactly. This property is essential for many biological functions, such as grasping and manipulating objects. I hope this explanation helps to clarify any confusion. Thank you for your interest in this topic.

Sincerely,