All questions
27 questions
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Are there infinitely many twin primes?
Pairs of primes just two apart, like 11 and 13, keep turning up however far we look. Nobody can prove they never stop.
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Can Linear A be deciphered?
We can sound out the writing of Minoan Crete, but we don't understand a word of the language behind it.
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Does P equal NP?
If a solution is easy to check, is it also easy to find? The answer decides what computers can ever do.
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How did language begin?
Every human society has language, and no other species has anything quite like it. How did it arise?
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How did life begin?
Somewhere on the young Earth, chemistry became biology. We still don't know how.
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How does general anesthesia switch off consciousness?
Doctors have used it safely for 180 years, yet nobody knows exactly how it turns the mind off.
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How does the brain bind perception into one picture?
Colour, shape and motion are processed in different parts of the brain. Why do we see one red ball rolling?
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How does the placebo effect work?
A sugar pill can ease real pain. How much of the effect is real, and how does belief change the body?
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Is the Collatz conjecture true?
Halve even numbers, triple odd ones and add one. Every number tried falls to 1. Nobody can prove that all of them do.
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Is the Riemann hypothesis true?
A single statement about where a function equals zero would tell us how the prime numbers are scattered.
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What is consciousness?
Why is there something it is like to be you?
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What is dark energy?
Something makes the expansion of the universe speed up. It makes up most of the cosmos, and we don't know what it is.
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What is dark matter made of?
Most of the matter in the universe gives off no light and has never been caught by a detector. What is it?
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What is glass?
Window glass looks solid and behaves like a solid, but its atoms are arranged like a liquid's. Why does a liquid stop flowing without ever crystallising?
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When did plate tectonics begin?
Earth is the only known planet with moving plates. Estimates of when they started range over three billion years.
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Why are there so many species?
Theory says that where species compete for the same few resources, one should win. In the ocean, thousands coexist. The "paradox of the plankton".
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Why did the Bronze Age civilisations collapse?
Around 1200 BC, a connected world of kingdoms fell within a few decades. Nobody agrees on why.
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Why do large neural networks generalise?
Networks with billions of parameters could simply memorise their training data. Instead they learn patterns that work on data they have never seen. Classical theory struggled to explain why.
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Why do some materials superconduct at high temperatures?
Some ceramics carry electricity with zero resistance far above the limits once thought possible. Forty years on, we still don't know how.
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Why do we age?
Our bodies repair themselves all the time, yet with the years they wear out. Why doesn't evolution prevent it?
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Why do we dream?
Every night the brain builds whole worlds that nobody asked for. Do dreams have a purpose?
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Why do we sleep?
Nearly every animal studied sleeps, even though it leaves them defenceless. What is sleep for?
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Why does déjà vu happen?
For a few seconds a new moment feels already lived, and we know it can't be. What is the brain doing?
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Why does Earth's magnetic field flip?
Hundreds of times in its history, magnetic north and south have swapped places. We can't predict when the next flip will come.
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Why does life use molecules of only one hand?
Chemistry makes left- and right-handed molecules in equal amounts. Life uses only one kind. Why, and how did it choose?
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Why does time have a direction?
The laws of physics barely distinguish past from future. We do. Where does the difference come from?
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Why is there more matter than antimatter?
The Big Bang should have made equal amounts of both, and they should have annihilated. Yet here we are.