Beam Therapy

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Before they affixed the mask over your head I held your hand firmly in mine, for my sake as much as yours, as you lay down on the couch. Shortly afterwards we were asked to leave the chamber.
Years earlier, when your mother and I were first dating, I slipped my fingers between hers as we walked back from dinner one evening. As I attempted to wax lyrical about the simple joys of holding hands and the contact between our skin, she couldn’t help but talk shop.
“No two surfaces ever really make contact,” she had explained. We were forever repelled some infinitesimal distance apart by the electrons on our skin, an insurmountable barrier separating us. I asked what happened if we stripped the electrons away, could the atoms underneath touch? She gave me the look I’d become all too familiar with for the next eleven years. A mix of mild condescension and excitement at the opportunity to share her world.
“Your body, everything around us, is most just empty space. The electrons and the nuclei in your atoms dance around, attracting and repelling one another electrically but the particles themselves hardly occupy space. It’s the interactions between them that create the illusion of solid matter.”
Sometimes I wished physicists had an off switch. Still, it was bizarrely romantic the way she’d told it.
When the doctor tells us they want to bombard you with radiation, I hear the same story again. Your mother, her hand in mine as we sat side by side, nodded sagely as the doctor explained how they planned to fire protons into your brain. Her calmness assuaged my panic. Apparently these protons, the cores of Hydrogen atoms, wreak havoc with the electrons in the targeted area, expelling them from atoms and disassembling DNA molecules, stopping the cells from reproducing. The biology I could just about wrap my head around but the physics made me shudder.
It hadn’t been long since they’d first found the tumour, an existential threat the size of a marble, in the region of your brain just behind your eyes. We heard talk of treatment plans, strategies, choices and all I wanted to know was whether or not you’ll survive; my world exists in binary. There are only two possibilities: yes or no. Instead, all they can do is give me probabilities, fatal wagers on my son’s life.
Your mother copes by abstracting everything, poring over journal articles and textbooks in the evenings after you’ve gone to bed. She patiently answers my concerns about the particles that will hurtle through you. Protons are charged much like the atoms in your body she explains. Yet unlike our hands, energetic protons have no qualms about shooting straight past the surface of your skin, navigating the empty space between the parts that comprise you.
She explains that every interaction between charged particles is governed by laws both mathematically exact, yet fundamentally indeterminate. No single proton will save you, a few will have to hurt perfectly healthy cells by energetically colliding with the DNA inside them that your mother and I gave you. The hope is that by tweaking the energy, shifting angles and focussing the particles like light through a lens, on average the protons will destroy your tumour much more than they destroy you. Like tipping the roulette wheel to better the odds.
Late at night when we lay besides one another, pretending to sleep, my incoherent thoughts turned to those protons, buffeted by the chance positioning of your molecules. Created in a nuclear forge and accelerated to breakneck speeds, the machine twists and turns them with magnets and directs a straight path for them to follow. Then reality kicks in, the world jostles them about and we can only hope they end up where they’re supposed to go, that their journey ends where it needs to. No sooner, no later.
When you were scarcely a toddler, I looked over your mother’s laptop screen as I rocked you sleep one afternoon and saw a paper she was reading: More is Different. I asked her for the gist of it and she told me that the behaviour of something made of many bits is fundamentally different to how all the individual bits act. Understanding atoms and even all their tiny subcomponents couldn’t tell you what they would do when you put them together.
Even the decades your mother spent studying physics and the nature of particles couldn’t have told her that a particular arrangement, plucked from infinite thermodynamic permutations, would give rise to you, a whole more than the sum of your parts. A being capable of giving us unbridled joy and breaking our hearts.
The treatment only lasts a minute or so. As we collect you from the room, you bound up to us and tell us you didn’t feel a thing, sporting the same grin you have at the top of the climbing bars in the park. I’m fine Dad!
That was the first time. We come back again and again, each time launching a fresh assault on the treasonous cells in your body. Heisenberg’s Uncertainty doesn’t hold a candle to mine. Until I know you’re safe, for good, no breath feels complete. I won’t know where our family is, or where it's headed until the cancer is gone but we keep fighting all the same. I begin to see that no matter how much I talk to your mother and the doctors to try and understand everything, the outcome is never fixed until it happens. All we can do is to collectively shift, bit by bit, the balance of probability in your favour.


About the Author: 
I'm a PhD student in Theoretical Particle Physics at University College London. I work on proton structure for applications at the Large Hadron Collider. When not doing physics, I enjoy books, black coffee, beer-fuelled conversations and board games. If you like my writing, you can read more at
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Quantum Theories: A to Z

I is for ...

Many researchers working in quantum theory believe that information is the most fundamental building block of reality.

K is for ...

These are particles that carry a quantum property called strangeness. Some fundamental particles have the property known as charm!

M is for ...
Many Worlds Theory

Some researchers think the best way to explain the strange characteristics of the quantum world is to allow that each quantum event creates a new universe.

A is for ...
Act of observation

Some people believe this changes everything in the quantum world, even bringing things into existence.

K is for ...

Quantum Key Distribution (QKD) is a way to create secure cryptographic keys, allowing for more secure communication.

P is for ...
Planck's Constant

This is one of the universal constants of nature, and relates the energy of a single quantum of radiation to its frequency. It is central to quantum theory and appears in many important formulae, including the Schrödinger Equation.

T is for ...

Quantum tricks allow a particle to be transported from one location to another without passing through the intervening space – or that’s how it appears. The reality is that the process is more like faxing, where the information held by one particle is written onto a distant particle.

A is for ...
Alice and Bob

In quantum experiments, these are the names traditionally given to the people transmitting and receiving information. In quantum cryptography, an eavesdropper called Eve tries to intercept the information.

T is for ...

This happens when quantum objects “borrow” energy in order to bypass an obstacle such as a gap in an electrical circuit. It is possible thanks to the uncertainty principle, and enables quantum particles to do things other particles can’t.

X is for ...

In 1923 Arthur Compton shone X-rays onto a block of graphite and found that they bounced off with their energy reduced exactly as would be expected if they were composed of particles colliding with electrons in the graphite. This was the first indication of radiation’s particle-like nature.

I is for ...

Some of the strangest characteristics of quantum theory can be demonstrated by firing a photon into an interferometer: the device’s output is a pattern that can only be explained by the photon passing simultaneously through two widely-separated slits.

R is for ...

The atoms of a radioactive substance break apart, emitting particles. It is impossible to predict when the next particle will be emitted as it happens at random. All we can do is give the probability that any particular atom will have decayed by a given time.

Q is for ...

One quantum bit of information is known as a qubit (pronounced Q-bit). The ability of quantum particles to exist in many different states at once means a single quantum object can represent multiple qubits at once, opening up the possibility of extremely fast information processing.

V is for ...
Virtual particles

Quantum theory’s uncertainty principle says that since not even empty space can have zero energy, the universe is fizzing with particle-antiparticle pairs that pop in and out of existence. These “virtual” particles are the source of Hawking radiation.

B is for ...
Bell's Theorem

In 1964, John Bell came up with a way of testing whether quantum theory was a true reflection of reality. In 1982, the results came in – and the world has never been the same since!

Q is for ...
Quantum biology

A new and growing field that explores whether many biological processes depend on uniquely quantum processes to work. Under particular scrutiny at the moment are photosynthesis, smell and the navigation of migratory birds.

M is for ...

Our most successful theories of cosmology suggest that our universe is one of many universes that bubble off from one another. It’s not clear whether it will ever be possible to detect these other universes.

E is for ...

When two quantum objects interact, the information they contain becomes shared. This can result in a kind of link between them, where an action performed on one will affect the outcome of an action performed on the other. This “entanglement” applies even if the two particles are half a universe apart.

H is for ...
Hidden Variables

One school of thought says that the strangeness of quantum theory can be put down to a lack of information; if we could find the “hidden variables” the mysteries would all go away.

R is for ...

Since the predictions of quantum theory have been right in every experiment ever done, many researchers think it is the best guide we have to the nature of reality. Unfortunately, that still leaves room for plenty of ideas about what reality really is!

W is for ...
Wave-particle duality

It is possible to describe an atom, an electron, or a photon as either a wave or a particle. In reality, they are both: a wave and a particle.

S is for ...
Schrödinger’s Cat

A hypothetical experiment in which a cat kept in a closed box can be alive and dead at the same time – as long as nobody lifts the lid to take a look.

N is for ...

When two quantum particles are entangled, it can also be said they are “nonlocal”: their physical proximity does not affect the way their quantum states are linked.

L is for ...
Large Hadron Collider (LHC)

At CERN in Geneva, Switzerland, this machine is smashing apart particles in order to discover their constituent parts and the quantum laws that govern their behaviour.

R is for ...

Unpredictability lies at the heart of quantum mechanics. It bothered Einstein, but it also bothers the Dalai Lama.

S is for ...

Quantum objects can exist in two or more states at once: an electron in superposition, for example, can simultaneously move clockwise and anticlockwise around a ring-shaped conductor.

Y is for ...
Young's Double Slit Experiment

In 1801, Thomas Young proved light was a wave, and overthrew Newton’s idea that light was a “corpuscle”.

H is for ...
Hawking Radiation

In 1975, Stephen Hawking showed that the principles of quantum mechanics would mean that a black hole emits a slow stream of particles and would eventually evaporate.

U is for ...
Uncertainty Principle

One of the most famous ideas in science, this declares that it is impossible to know all the physical attributes of a quantum particle or system simultaneously.

F is for ...
Free Will

Ideas at the heart of quantum theory, to do with randomness and the character of the molecules that make up the physical matter of our brains, lead some researchers to suggest humans can’t have free will.

A is for ...

This is the basic building block of matter that creates the world of chemical elements – although it is made up of more fundamental particles.

C is for ...

The rules of the quantum world mean that we can process information much faster than is possible using the computers we use now.

L is for ...

We used to believe light was a wave, then we discovered it had the properties of a particle that we call a photon. Now we know it, like all elementary quantum objects, is both a wave and a particle!

D is for ...

Albert Einstein decided quantum theory couldn’t be right because its reliance on probability means everything is a result of chance. “God doesn’t play dice with the world,” he said.

G is for ...

These elementary particles hold together the quarks that lie at the heart of matter.

P is for ...

Quantum mechanics is a probabilistic theory: it does not give definite answers, but only the probability that an experiment will come up with a particular answer. This was the source of Einstein’s objection that God “does not play dice” with the universe.

B is for ...
Bose-Einstein Condensate (BEC)

At extremely low temperatures, quantum rules mean that atoms can come together and behave as if they are one giant super-atom.

S is for ...
Schrödinger Equation

This is the central equation of quantum theory, and describes how any quantum system will behave, and how its observable qualities are likely to manifest in an experiment.

G is for ...

Our best theory of gravity no longer belongs to Isaac Newton. It’s Einstein’s General Theory of Relativity. There’s just one problem: it is incompatible with quantum theory. The effort to tie the two together provides the greatest challenge to physics in the 21st century.

Z is for ...
Zero-point energy

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O is for ...
Objective reality

Niels Bohr, one of the founding fathers of quantum physics, said there is no such thing as objective reality. All we can talk about, he said, is the results of measurements we make.

C is for ...

People have been hiding information in messages for millennia, but the quantum world provides a whole new way to do it.

W is for ...

The mathematics of quantum theory associates each quantum object with a wavefunction that appears in the Schrödinger equation and gives the probability of finding it in any given state.

J is for ...
Josephson Junction

This is a narrow constriction in a ring of superconductor. Current can only move around the ring because of quantum laws; the apparatus provides a neat way to investigate the properties of quantum mechanics and is a technology to build qubits for quantum computers.

U is for ...

To many researchers, the universe behaves like a gigantic quantum computer that is busy processing all the information it contains.

D is for ...

Unless it is carefully isolated, a quantum system will “leak” information into its surroundings. This can destroy delicate states such as superposition and entanglement.

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