John Gribbin2019Shortlisted, Royal Society Science Book Prize
The Mystery of the Quantum World
Quantum physics works perfectly and makes no sense. Every attempt to say what it means asks you to believe one impossible thing. This short book lays out six of them, side by side, and lets you choose.
The core idea
John Gribbin is a British science writer trained in astrophysics, and the author of many popular books on physics, including In Search of Schrödinger's Cat. Six Impossible Things is a short book about what quantum physics means, not about how to calculate with it. It first sets out the basic puzzles of the quantum world, including the experiment in which single particles pass through two slits and still build up a pattern of stripes. It then gives a few pages each to six interpretations: Copenhagen, pilot wave, many worlds, decoherence, the ensemble view and the transactional interpretation. The title nods to the White Queen in Through the Looking-Glass, because each interpretation asks you to believe something that sounds impossible. Gribbin presents the book as an agnostic overview: none of the six comes out as better or worse than the others.
The book's point is easy to miss: the interpretations are not rival theories in the usual sense. They agree on what you will see in the lab. They disagree about what is happening when nobody is looking, and so far no experiment has settled it.
So Gribbin does not ask which one is true. He asks what each one costs. Each buys a sensible picture somewhere by accepting something strange elsewhere: no reality before measurement, a wave linking everything at once, countless worlds, or signals from the future.
First
Quantum theory predicts what experiments show with great precision. That part is not in question.
Second
What a particle is doing between source and screen is where the six interpretations part ways.
Third
All six are strange. Some are stranger than others, and in the quantum world, stranger does not mean more wrong.
Interactive · the experiment with two holes
Each particle lands as a single dot. Keep firing and see what the dots build. Then switch on the detector, which notes which slit each particle used, and run it again. Below the screen, pick the impossible thing you would rather believe, and read how it explains what you just saw.
Detector off · stripes allowed
Fire one particle and see where it lands.
Each slit sends out a wave, ψ₁ and ψ₂. The chance of a dot landing at a point is the square of what arrives there.
No detector: add the waves, then square.P = |ψ₁ + ψ₂|²
Detector on: square each, then add. The cross term that draws the stripes is gone.P = |ψ₁|² + |ψ₂|²
Far from the slits the first one becomes the textbook cos² × sinc² pattern.
HourLife's simplified model, drawn with real two-slit maths. Each dot is a random draw from that chance, so no two runs look the same. Your settings stay in this browser.
Every interpretation gets the same dots. They disagree about what made them. Pick one and read its account of the run you just did; flip the detector to read the other half.
Choose one of the six to read its story of your experiment.
The impossible thing
Your run, detector off
The one-line summaries are HourLife's shorthand for each view, not Gribbin's text. Physicists who hold these views would add many footnotes.
Concept anatomy
Strip the two-slit experiment down and four observations are left. Any interpretation has to account for all of them. Then the ledger: what each story keeps that common sense wants, and what it gives up.
Three things common sense wants, and the price each interpretation pays to explain the four facts. HourLife's shorthand for the standard versions; experts argue about the edges.
| Interpretation | A particle has a definite path | There is only one world | Causes come before effects | The impossible part |
|---|---|---|---|---|
| ICopenhagen | No | Yes | Yes | Nothing is real until measured |
| IIPilot wave | Yes | Yes | Yes | A wave that links everything at once |
| IIIMany worlds | No | No | Yes | Endless branching worlds |
| IVDecoherence | Looks so | Looks so | Yes | Possibilities hidden, not gone |
| VEnsemble | Doesn't say | Yes | Yes | Silent about single particles |
| VITransactional | After the handshake | Yes | No | Waves from the future |
Community insights
HourLife's takeaways from the book, ranked by reader votes. Vote for the ones that made the quantum world click, or at least feel less impossible.
I♠HourLife takeaway
The equations of quantum mechanics have passed every experimental test so far, to great precision. The interpretations are different stories about the same results. That is why Gribbin can treat all six side by side: none of them is ruled out by an experiment yet.
II♥HourLife takeaway
The title borrows from the White Queen in Through the Looking-Glass, who practises believing impossible things before breakfast. Gribbin's point is that all six interpretations are crazy in some way. Some are crazier than others, but in the quantum world, crazier does not mean more wrong.
III♦HourLife takeaway
Each particle lands as a single dot. Yet after thousands of them, the dots form an interference pattern, as if each one had passed through both slits. Put a detector at the slits to see which way each particle went, and the stripes disappear. Every interpretation in the book has to explain this.
IV♣HourLife takeaway
This is the interpretation associated with Niels Bohr, and the name came from Werner Heisenberg. The wave describes what you can know, and a measurement turns the spread of possibilities into one result. It became the textbook answer, and Gribbin shows how much it leaves unexplained.
V♠HourLife takeaway
Louis de Broglie proposed the idea in the 1920s, and David Bohm revived it in the 1950s. The wave goes through both slits and the particle through one, guided by the wave. The price is that the wave links everything at once, so what happens here depends on the whole set-up, however far apart its parts are.
VI♥HourLife takeaway
Hugh Everett's idea from the 1950s keeps the equations exactly as they are and never lets the wave collapse. Instead, each measurement splits reality into branches, one for each outcome. It is the simplest maths and the largest universe.
VII♦HourLife takeaway
A quantum system is never truly alone. Air, light and the measuring device all interact with it, and that contact washes out interference very quickly. The question this leaves open is why you then see one particular outcome.
VIII♣HourLife takeaway
An ensemble can be many identical trials, such as one electron sent through the same set-up a million times. Read that way, quantum theory is statistics and nothing more, which is why it is called a non-interpretation. It looks sensible until the system starts to interact with the world around it, and puzzles such as the watched pot, where a closely watched system does not change, start to bite.
IX♠HourLife takeaway
Physicist John Cramer's interpretation has an offer wave going forward from the source and an answering wave coming back from where the particle will land. Where they meet, the transaction is complete. The equations allow waves in both directions of time; this view takes both seriously.
Action steps
Use the simulator on this page. Fire particles one at a time until the stripes appear, then switch on the detector and watch them go. Write one sentence about what surprised you.
In a dark room, shine a laser pointer through two thin slits cut close together in kitchen foil, or past a single hair, onto a wall a few metres away. Look at the wall, never into the beam.
Give each interpretation one card: its name, who proposed it, and the one impossible thing it asks you to accept, in your own words. Check them against the book.
Choose the interpretation you would rather believe and write two lines on why. Add one line on what evidence would change your mind.
Read chapter 5 of Lewis Carroll's Through the Looking-Glass, Wool and Water, where the title comes from. It is short, out of copyright and free online.
Once a week, explain one interpretation to a friend in two minutes, without jargon. Where you get stuck is the part to reread.
When you read a science headline, write down what was actually measured, then the story told about it. Notice how often the two get blurred.
Before you argue a point this week, say the opposing view in a form its holder would accept. Gribbin does this for six rival stories in a row.
Once a week, note one fact that sounds impossible and the evidence that it is true. Read the list back at the end of the month.
Quantum physics never tells you which story is true. It only tells you that every story costs one impossible thing.HourLife note after John Gribbin
Pick setup actions and daily habits from Six Impossible Things: The Mystery of the Quantum World, choose a start date, and download a printable checklist with real calendar pages.
John Gribbin is a British science writer trained in astrophysics, and the author of many popular books on physics, including In Search of Schrödinger's Cat. Six Impossible Things is a short book about what quantum physics means, not about how to calculate with it. It first sets out the basic puzzles of the quantum world, including the experiment in which single particles pass through two slits and still build up a...
HourLife’s key takeaways include: Nobody argues about what quantum theory predicts; the fight is over what is really going on. Every way of making sense of the quantum world asks you to accept one thing that sounds impossible. Send particles through two slits one at a time, and they still build up stripes that only waves should make.
It's a strong pick for readers exploring Learning & Mastery and Modern Philosophy Basics. HourLife distills its core idea into key insights and practical actions worth trying.
Run the two-slit experiment — Use the simulator on this page. Fire particles one at a time until the stripes appear, then switch on the detector and watch them go. Write one sentence about what surprised you.
About five minutes. The HourLife summary distills Six Impossible Things: The Mystery of the Quantum World into its core idea, 9 community insights, and 9 practical actions you can apply right away.
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