The Other Entanglement

 

A year ago I wrote a blog entry which included  “entanglement” – a complicated quantum mechanics concept where multiple particles … never mind. (If you’re interested, go and look for the February 2021 blog “Schroedinger’s Bird ??????”.

This other entanglement is more easily understood. Why does hair tangle and how do you get it untangled?

When you look at hair under a microscope, you can see that the core of the hair is covered with cuticles. Think of them as being like the scales of a fish. Both the cuticles and the core of the hair are made up of keratin – helix-shaped protein molecules. The cuticles are covered with sebum, an oily substance which protects the hair from drying out. 

 

                                         A single human hair, showing the cuticles

Because hairs are not smooth, if two meet at the right (wrong?) angle, they can snag on each other. If hair is damaged, cuticles may be missing, torn, or more protruding, and the tangling will be worse. Not all hair is the same, of course. Hair ranges from fine to coarse in thickness, and from straight to curly. It’s not a simple problem to figure out what hair will tangle more. A head of hundreds of thousands of strands colliding in all directions is just the sort of knotty problem that mathematicians and physicists love to tackle. Some fine work done by Jean-Baptiste Masson, a brain imaging researcher at the École Polytechnique in France showed that, although curly hairs cross more often than straight, the angle at which the hairs meet is most important. Counter-intuitively, straight hair tangles more than curly. And what appears to be the most important factor is the diameter of the strands. Fine hair tangles more than coarse hair.

 How to Untangle Hair

 Less surprising than the study of what hair tangles most, is the result of work done by a team of scientists at Harvard. They found — drum roll, please — that untangling hair is best done by starting to comb close to the ends and then working your way up to the scalp.

You can also get some help from the magic of chemistry. There are dozens of commercial Detangling Sprays available. My favourite — based solely on the name — is this one:

 The name is based on the widespread myth in Southern Africa that elephants eat the fermented fruit of the Marula tree, get drunk on the alcohol, and rampage around, causing widespread destruction. And of course, what could be more effective at detangling your hair than a rampaging drunken elephant?

The active ingredients in detangling sprays are

• Oils. These replace missing sebum, making hair softer and less likely to tangle.
• Silicone. A substance with long molecular chains that bind to the surface of the hair and make it glossy, smooth and less likely to tangle.
• Acidifiers. Lowering the pH of the hair strengthens the hydrogen bonds between keratin molecules. This smooths and tightens the surface cuticles on each strand.
• Hydrolyzed Protein. Amino acids which are the building blocks of proteins. These help to repair damaged keratin, smoothing broken edges of the cuticles.
• Surfactants. These molecules have one part which binds to the exposed keratin, between damaged cuticles; the other end of the molecule is hydrophobic (repelling water) and creating a smooth thin film that’s easier to comb.

 Preventing tangles – Shampoo and Conditioner

Shampoos are detergents which do one simple job: remove dirt from hair. The dirt is caught up in the oily sebum and the detergent washes it away. Detergents are molecules with one end which is attracted to oil and the other end attracted to water. So one end binds to the dirty, oily sebum and rinsing with water washes away that dirty oil. Any detergent would effectively wash away the dirt. Soap, which is also a detergent, would do that. If you live in Vancouver, which has ‘soft’ water, soap should work quite well instead of shampoo. If you live in Montreal or Kitchener/Waterloo, which have ‘hard’ water, not so much. ‘Hard’ water has dissolved salts of calcium and magnesium, and soap reacts with them to form a deposit: “soap scum”. You don’t really want that coating your hair after you wash it; you need a detergent other than soap.

Some other considerations:

• shampoos are pH balanced – between 5 and 8. Outside of that range, the cuticles will not lie flat.
• The detergent must not be too strong. If it is, it will remove all of the sebum, along with the dirt, and your hair will end up too dry.
•  Shampoos always include a foaming agent. This has absolutely no use except to make the user feel as though the shampoo is working. If the shampoo doesn’t foam, people won’t buy it.

Even with a mild detergent, conditioners are helpful in replacing the sebum that’s been removed. How do conditioners work and what are their active ingredients? Conditioners are actually the same as detanglers, so they are just like that descrition above. Yes, you can use a conditioner as a detangler, especially the conditioners that are designed to be left on your hair and not rinsed off.

Final snippet: 2 in 1 Shampoo & Conditioners are great for saving time. You wash and condition your hair in one step, not two. But how do they work? How does the conditioner “know” that it should wait for the shampoo to remove the sebum before coating the hair? Clever chemistry holds silicones in suspension in a shampoo until the shampoo is rinsed away with a lot of water. So, during the shampooing the silicones are held in a sort of suspended state of animation. When the shampoo is washed out, the silicones are activated, coat the hair and leave it in good condition. The results can be pretty good, but still 2 in 1's can’t match the effectiveness of separate shampoo and conditioner.

 

Schroedinger's Bird ???????

 Quantum Mechanics is weird. In a quantum world of photons and sub-atomic particles, things behave very differently from the world that we can observe and know. It’s extremely difficult to understand that light is both a photon particle and a wave. It’s very hard to believe that a particle doesn’t have a specific property until you measure it. And until then it has all the possible properties you might measure. Famously, Einstein himself didn’t believe this, saying “God doesn’t play dice with the universe”. 

 

Courtesy: Jadvani_Sharad at Pixabay.com

 

Equally famous is the argument that Erwin Schroedinger used to illustrate this apparent impossibility. Schroedinger described a “thought experiment”, where there is a cat and a radioactive atom sealed inside a box. There is also a Geiger counter, which will detect radiation if and when the atom decays. If it detects radiation, it breaks a flask of poison which kills the cat.  The only way to find out if radiation has been detected is to open the box. According to quantum theory, until that is done, the radiation both has and hasn’t occurred, and therefore the cat is both alive and dead until the box is opened.

Diagram of Schrödinger's cat thought experiment.
Roughly based on Schroedingerscat3.jpg. Dhatfield-own work. CC Creative Commons.

Einstein, with Boris Podolsky and Nathan Rosen, published another thought experiment (called the EPR paper) which demonstrated another paradox. This thought experiment showed another seemingly ridiculous outcome of quantum mechanics math. It went (more or less) like this:

• ·         Two particles are set in motion towards each other with the same momentum. They interact with each other briefly at a known position.
• ·         This relationship between the two particles is called “entanglement”.
• ·         These particles have a range of momentum and location. Until you measure them, they have all of those with some probability. (Yes, hard to believe, but that's what quantum mechanics math says).
• ·         When you measure, say, the momentum of one of the two articles it resolves to have only the one measured momentum.
• ·         But magically, as you do that, the second particle, which may have travelled anywhere in the universe, resolves its momentum to the same value.(How it know to do this, and at the same instant?)
  

It seemed clear to Einstein that this kind of action-at-a-distance was impossible. He said it therefore followed that quantum mechanics was incomplete. There must be some additional factor that was being overlooked and which could explain this paradox.

Shockingly, experiments in the 1970’s and 80’s showed that entanglement is not impossible, but a real phenomenon. Hard to believe, but true.

And now to birds. No, Schroedinger didn’t really do any thought experiments on birds. Sorry.

Birds are astonishingly good at finding their way over vast distances. Homing pigeons have been used for centuries to carry messages back to their homes from hundreds of kilometers away. Some species of birds migrate thousands of kilometers each season, and find their way back to the nest that used in the previous season.

Some slightly nasty scientists have tested migrating abilities. They captured 30 white-crowned sparrows near Seattle migrating South from Alaska to Southern California. They packed the birds into crates and flew them 2,300 miles to Princeton, New Jersey. When they released them, the adult sparrows set off in a direct course South-West toward Southern California. 

 

White-crowned Sparrow. Photo: Steve Ryan, CC BY-SA 2.0, via Wikimedia Commons

Even hummingbirds, with brains the size of a pea, put human navigation abilities to shame. A researcher described finding a hummingbird hovering opposite the hook where he hung a feeder each year. He was planning to put it out in a few days' time. The hummingbird showed up earlier than expected, and remembered exactly where the feeder was supposed to be. 

Photo: Simon Shapiro

 We don’t know exactly how birds are able to navigate so well. It’s clear that they use multiple strategies, including:

• ·         Following rivers, mountains or the seashore
• ·         Using senses of smell and sound, both of which are far more acute than humans’.
• ·         Navigating using the sun and stars. Like ancient mariners they might be using these to identify their latitude and longitude. 
  

But the really mysterious ability is that birds are able to sense the earth’s magnetic field. This requires exquisite sensitivity. Scientists have been working for decades to figure out how the mechanism works.

Birds need some light to do it. Not much, because even the dim light of stars at night is enough. But total darkness inhibits the ability.

Enter Entanglement

There is growing consensus that the ability involves crytochrome, a light-sensing protein that exists in birds’ eyes. A photon colliding with crytochrome can disturb electrons in two molecules, creating an entangled radical pair of molecules, each with an odd number of electrons. They return to equilibrium very quickly – about 100 microseconds. During that time, they can flip-flop between two states of electron spins – each molecule changing at exactly the same time, because of the entanglement. The relative time spent in each of the two states can be influenced by the earth’s magnetism. And each state can participate in different chemical reactions, producing different chemicals. These product chemicals – as yet unidentified – could be the mechanism for the bird’s brain to sense magnetism. 

 Scientists are working on harnessing entanglement to build quantum computers. It seems that birds (and evolution) beat us in the race to make practical use of quantum entanglement.