“Curiouser and curiouser!” Cried Alice (she was so much surprised, that for a moment she quite forgot how to speak good English).
Lewis Carroll, Alice’s Adventures in Wonderland
Life, uh, finds a way.
Dr. Ian Malcolm, Jurassic Park
One of the most fascinating phenomena in nature is the migration of various birds and animals. Monarch butterflies fly upto 3000 miles southward across the US every season to central Mexico. Green turtles that hatch on the shores of Ascension Island in the South Atlantic swim across thousands of miles before returning every three years. These animals use a variety of techniques for navigation: solar navigation during the day and celestial navigation during the night; memorising geographical landmarks; and some can even smell their way to their destinations.
The European Robin stands out amongst the migratory species due its use of a novel navigational technique: using the earth’s magnetic field for direction. The property of sensing the strength and direction of earth’s magnetic field is known as magnetoreception. Until recently, the mechanism of magnetoreception remained a mystery.
Here’s the problem. The earth’s magnetic field is very weak, about 30-70 μT or about 1/100 th of the strength of your typical fridge magnet. In order to sense this field, it must be able to induce a chemical reaction in the Robin’s body by interacting with the molecules in a living cell. But the energy of this interaction is less than a billionth of the energy that is needed to make or break a chemical bond. In other words, the earth’s magnetic field is too weak to have any effect on the molecules in a Robin’s living cell. If that is the case, then how is the Robin detecting this magnetic field?
To solve this and several other biological mysteries, we have to turn to quantum mechanics. The marriage of biology and quantum mechanics has led to a new research area in the last decade known as quantum biology. A remarkable introductory book on the subject is Life on the Edge by Johnjoe McFadden and Jim Al-Khalili.
To get a feel of quantum biology, we must first get acquainted with quantum mechanics.
Narrator : (Ooooh how I have waited for this day when this author would stop writing about movies of which he knows nothing and start writing about science of which he knows even less. It’s Go Time!) So, I understand that you are a physicist.
Me (Feeling proud) : Yes, I have a PhD in physics, specialising in microscopy which…
Narrator : Ah, which, switch, go to the beach, eat a sammich. Can you explain the concept of electron spin?
Me : Sure. Assume that the electron is like a tennis ball and it’s spinning around its axis…
Narrator: But the electron is nothing like a tennis ball..
Me : Well, yes…
Narrator : And the electron spin is nothing like a tennis ball spinning..
Me : Yes, but…
Narrator : If one thing is not analogous to another thing, why give the analogy in the first place? It’s like saying a cow is analogous to a lion.
Me : (swallows) Yaargh…
Narrator : Okay, let’s change the subject.
Me (relieved) : Yes, please.
Narrator : What happened before the Big Bang?
Me : Yaart…
Narrator : My work here is done. I will be back!!
Jokes apart, good science communication is incredibly difficult. I have learned physics from textbooks but it was the popular science books that really drove the ideas home. A great example is George Gamow’s Mr. Tompkins in Wonderland that explains relativity, quantum mechanics and many other topics through stories where Mr. Tompkins goes wandering around the atomland. And for a lucid account of what happened in the first three minutes after the Big Bang, Steven Weinberg’s The First Three Minutes is a great read. These two books should be a required reading for all 11+ year old kids. Next time you have a kid’s birthday coming up, gift her these books. They may get her interested in science and change her life. (Gamow’s book has a little bit of maths that can be skipped; Weinberg’s book is free from maths!)
I think I can safely say that nobody understands quantum mechanics.
Richard Feynman
If your first encounter with quantum mechanics leaves you baffled, fear not for you are in good company. Even a mind as brilliant as Albert Einstein could not come to terms with the workings of quantum mechanics, hence the famous quote, “God does not play dice.” So why is quantum mechanics so difficult to comprehend?
As things start getting smaller, they start acting strangely in ways that defies common sense. So an electron does not behave like a tennis ball. When a tennis ball hits a wall, it will bounce back. When an electron hits a barrier, some part of it may “leak” through the barrier because sometimes an electron behaves like a wave. When you hear a sound of a car passing outside your house, that’s because the sound waves can pass through the walls of your home. Similarly, an electron can pass through barriers in a phenomenon known as tunnelling.
Now, the barrier an electron usually faces is not the wall of your home but an energy barrier. Since it’s a wave it can “tunnel” through the energy barrier. In other words, even when enough energy is not available to complete a reaction on paper, in reality the reaction occurs because electrons behave like waves. This is the solution to the problem of how an European Robin can sense the earth’s magnetic field, even though the field is weak. For details on exactly how this happens, you need to read the book.
Electrons, protons, atoms, and molecules behave in strange ways in the quantum world. If we could shrink ourselves and see the quantum world in action, it would be like a reenactment of Alice’s Adventures in Wonderland. Wouldn’t it be great to watch a movie where the characters travel to the quantum world and experience the laws of quantum mechanics? Something like what Interstellar did with black holes?
The Equation of Life
You know how the internet is always trying to find the most incredible things, like a place where gravity does not work and so on? (No idea why throwing a water bottle to make it stand upright is such a fascinating endeavour for Gen Z.) Well, one of the most amazing creations of nature is right there in your backyard – trees. Plants and tress are highly underrated. They are the magical creatures who make leaves, roots, fruits and huge branches literally out of thin air. The equation that governs this process is that of photosynthesis and it’s deceptively simple.
6CO2 + 6H2O → C6H12O6 + 6O2
DIY Photosynthesis
Why should plants have the monopoly? Do your own photosynthesis at home and get 100% homemade organic sugar for free!!!
Recipe : Take six molecules of carbon dioxide. Make sure they are of good quality. Acetylene and mercuric chloride molecules have the same shape and there have been reports of counterfeit CO2 molecules in the market. Make sure the carbon-oxygen bond is strong by pulling them apart. Don’t worry, it’s a covalent bond. It won’t break. Put the molecules in a bowl and add exactly six molecules of water. Tap water should be fine. Sprinkle a pinch of chlorophyll and place the bowl in sunlight and in no time you will have your homemade 100% organic sugar.
Disgruntled_user : Tried it, doesn’t work. The water evaporated and I got throat infection from inhaling the CO2 molecules. Chlorophyll tasted like broccoli gone bad and gave me hiccups.
Titan_mom78 : Same here, minus the throat infection or hiccups. I wanted to use the sugar to bake watermelon cake. Does photosynthesis really work?
Mumu33 : I blame the sunlight. Call me suspicious but the quality of sunlight is not what it used to be.
Titan_mom78 : Exactly! 4.5 billion years with the same white light and no upgrades. At least give us some more colours! Is that too much to ask?
Mumu33 : Seriously, my cousin moved to Proxima Centauri b last year and he cannot stop bragging about their three stars. He calls the solar system ‘one star dictatorship.’ Says that now he has progressed to a democratic three star system. And one of them is a red dwarf for crying out loud. You need a telescope to see it. Ugh!
I have always loved plants but after reading this book, whenever I look at a simple leaf, I am astounded. Let me explain why.
The reaction above, while correct, is simplistic. A whole lot of intricate steps must happen precisely before a plant can convert thin air into sugar. The leaves of a plant capture the sunlight photons (photons are the particles of light) and carry this energy from the chlorophyll antenna to a place called reaction centre, where this energy is utilised for chemical reactions. But these reaction centres are quite far from the place where the photon was captured so the energy packet passes from one molecule to the next, much like a baton in an athletic relay race.
The interior of a leaf is a densely packed forest of chlorophyll molecules. If left to chance, the energy packet may take right path and reach the reaction centre or it may not. However, this process of transfer of captured photon energy to the reaction centre boasts the highest efficiency of any known natural or artificial reaction : close to 100 percent!! That means almost every energy packet finds the correct path to the reaction centre. But how does it do that? This has been one of the biggest puzzles in biology.
The problem itself is well known in computational science as the ‘travelling salesman’ problem. What route should a travelling salesman take in order to maximise his profits and minimise the costs? As the number of cities that the salesman is going to visit increases, the problem becomes increasingly challenging, solvable only by very powerful computers. So how is a simple plant in your backyard solving this problem?
In 2007, Greg Engel, Graham Fleming and coworkers at the University of Berkeley in California proposed a solution based on experimental data. In simple terms, it’s this. Instead of imagining the energy packet as a photon particle, we can imagine it as a wave spreading through all possible routes at once. In other words, we must invoke quantum mechanics in order to understand this process. A rough analogy would be how water, when poured on the floor always finds the sloped path, travelling as a wave.
When the packet is treated as a wave, it can simultaneously follow all possible routes and find the best one. In fact, this is exactly what a quantum computer would do when solving such a problem. As expected, this claim took the biology world by storm and while there have been reservations from some scientists, more and more experimental data using advanced techniques such as “two-dimensional Fourier transform electronic spectroscopy” (2D-FTES) strongly suggests the possibility that plants are using advanced quantum computing for photosynthesis.
The theoretical framework of quantum mechanics was formulated in the 1930s and 1940s. So why did it take so long for the scientists to discover its effects in biology? The main reason behind this was that biology is inherently messy. While quantum mechanics has been proven right again and again, it was always in laboratories with extremely well controlled conditions such as ultra high vacuum and low temperatures. The quantum phenomena are delicate and disturbances such as external noise from environment destroy their quantum nature. That’s why the quantum computing labs have highly sophisticated experimental conditions. Naturally, no one thought that the cell with its wet, messy environment would be a place where quantum mechanics would be applicable.
It turns out that nature has devised ingenious methods in order to preserve the delicate quantum nature inside the cell. In case of photosynthesis, the surrounding molecules vibrate from thermal energy at one frequency and the chlorophyll molecules vibrate at a different frequency. Both of these act in tandem to preserve the delicate quantum nature of the energy packets as they travel to the reaction centres.
As the field of quantum biology blossoms, scientists are finding more and more examples of biological phenomena that can only be explained by quantum mechanics. How can we identify over 10,000 distinct smells when we only have a few hundred olefactory receptors? How do the DNA molecules maintain their very high fidelity rates while copying the genetic code? In fact, applying quantum biology to genetics is expected to uncover some of the deepest mysteries.
The accepted theory of evolution goes something like this. Random genetic mutations occur in our genes and those that are favourable survive and pass on those mutations. In other words, the mutations happen by accident and it is sheer chance that this eventually leads to a better mutation.
In September 1988, an eminent geneticist called John Cairns at the Harvard School of Public Health published a paper on genetic mutations in E. coli bacteria. Cairns used a particular strain of E. coli that, due to a genetic defect, was unable to digest lactose. He introduced these bacteria in a dish that contained only lactose. For a few days, the bacteria just hung around the gel, but they did not die as was expected. Then they started to grow. The bacteria had corrected the genetic error and were now consuming lactose! They were responding to the environment. But this was against the evolution theory of random mutations. So what was really happening?
It turns out that the phenomenon can be explained using quantum mechanics, in particular by assuming that the atoms in the DNA strands behave as quantum particles. The detailed explanation is little bit involved and can be best understood from the book.
So how much of our genetics, our diseases and indeed our health is dependent on quantum mechanical phenomena? The authors propose a three layered nature of reality. The top layer is Newtonian mechanics with which we fly rockets, operate machines etc. Second layer is thermodynamics that deals with everything from working of an air conditioner to our bodies sweating it out in summer. And the third layer is quantum mechanics that operates only in specific situations but has profound effects on the way we live our lives.
