Science

Twenty questions. Yes or no answers only. Somebody thinks of a thing, and you have to find it. The number twenty looks like a folk choice, the sort of round figure a Victorian parlour settles on. It is not. Twenty is very close to exactly the right number, and you can derive it. Every question is worth one bit, at best A yes-or-no answer can carry at most one bit of information. One bit halves the space of possibilities. Ask a perfect question and whatever the answer, you throw away half the world. ...

Search this and you get a list. Rodents, rabbits, birds, insects, earthworms, berries, carrion, and whatever fell out of your bin. Every source has the same list because the list is correct. It is also useless, in the way that a list of things a car can run into is useless if what you wanted to know was how fast it goes. I wanted the number. How much food does a fox actually need, in a day, and what does that imply about how it spends its time? The answer turns out to explain the list. ...

I asked whether intelligent life on another planet would follow anything like our evolutionary path, or whether humans are a one-off. Everybody who answers this question reaches for the same argument, and I reached for it too before I checked it. It is a good argument. It is also, in the specific form everyone uses, wrong. The argument everybody makes Evolution repeats itself. Give it the same problem twice and it finds the same answer twice, so the features that keep reappearing on Earth are the features we should expect anywhere. ...

I went into this expecting the Sun to have been more or less constant for the whole history of life, wobbling a bit with sunspot cycles. That is wrong, and it is wrong by a lot. It is also a question that answers itself slightly sideways. The Sun is getting brighter, dramatically so. It is barely getting hotter. Those are different things, and the gap between them is the interesting part. ...

You have heard this one. Every seven years, every cell in your body has been replaced, so you are a physically new person, and the coffee stain you feel guilty about was technically spilled by somebody else. It is a lovely thought and it is not true. Some of the cells reading this sentence have been with you since before you were born. We know that with unusual confidence, and the reason is grim and wonderful. Between 1955 and 1963 the world tested nuclear weapons in the atmosphere, and in doing so accidentally wrote a date stamp into every living thing on the planet. ...

Last October I asked whether you could engineer a human, or any mammal, to run on sunlight the way a plant does. I expected a biology answer, something about genes and organelles and immune rejection. What I got was arithmetic, and the arithmetic ends the argument before biology gets a turn. The answer everyone gives is the weakest one Search this question and the first thing you will read is that humans cannot photosynthesize because we have no chloroplasts and produce no chlorophyll. ...

Flying from Auckland to Santiago takes about eleven hours. Coming home takes closer to thirteen. The explanation everyone reaches for is that the Earth spins eastward, so on the way east the destination comes to meet you, and on the way back you have to chase it. This is wrong, and it is wrong in a way I find genuinely satisfying, because the thing people are blaming turns out to be responsible after all. Just not for the reason they think. ...

I asked a question I had heard the answer to a hundred times: is it true that half the cells in my body are foreign bacteria? The answer turns out to be yes, roughly. Which is strange, because the version everyone repeats is that bacteria outnumber your own cells ten to one, and that version is wrong. The numbers In 2016, Ron Sender, Shai Fuchs and Ron Milo went and did the arithmetic properly. For a reference adult male of 70 kg: ...

The question I typed was “is the caspian sea salty?”, which I assumed had a one word answer. It has a one sentence answer. The Caspian Sea has a salinity of about 1.2%, or 12 grams per litre, which is roughly a third of the salinity of average seawater. So yes, it is salty. It is brackish rather than briny. You would not want to drink it, and you would not mistake it for the Pacific either. ...

My wife told me an amazing fact she had picked up from a Russian account on TikTok. For years, the story goes, scientists believed bats were extremely good at echolocation. That was how they flew around dark caves without constantly hitting the walls. Then one scientist X-rayed a batch of bats and found that many of them carried multiple healed fractures. Bats were not brilliant navigators after all. They were terrible at echolocation, crashing into things and breaking bones the whole time. They were just extraordinarily good at healing. ...