In practice, the thing that will kill you in space is simply the lack of air. In 1965 a test subject’s suit sprang a leak in a NASA vacuum chamber. The victim, who survived, remained conscious for about 14 seconds. The exact survival limit isn’t known, but would probably be one to two minutes.
7. Atomic collapse
The atoms that make up your body are mostly empty space, so despite there being so many of them, without that space you would compress into a tiny volume. The nucleus that makes up the vast bulk of the matter in an atom is so much smaller than the whole structure that it is comparable to the size of a fly in a cathedral. If you lost all your empty atomic space, your body would fit into a cube less than 1/500th of a centimeter on each side. Neutron stars are made up of matter that has undergone exactly this kind of compression. In a single cubic centimeter of neutron star material there are about 90.7 million tonnes of matter. An entire neutron star, heavier than our sun, occupies a sphere that is roughly the size across of the Isle of Wight.
8. Electromagnetic repulsion
The atoms that make up matter never touch each other. The closer they get, the more repulsion there is between the electrical charges on their component parts. It’s like trying to bring two intensely powerful magnets together, north pole to north pole. This even applies when objects appear to be in contact. When you sit on a chair, you don’t touch it. You float a tiny distance above, suspended by the repulsion between atoms. This electromagnetic force is vastly stronger than the force of gravity — about a billion billion billion billion times stronger. You can demonstrate the relative strength by holding a fridge magnet near a fridge and letting go. The electromagnetic force from the tiny magnet overwhelms the gravitational attraction of the whole Earth.
9. Stardust to stardust
Every atom in your body is billions of years old. Hydrogen, the most common element in the universe and a major feature of your body, was produced in the big bang 13.7 billion years ago. Heavier atoms such as carbon and oxygen were forged in stars between 7 billion and 12 billion years ago, and blasted across space when the stars exploded. Some of these explosions were so powerful that they also produced the elements heavier than iron, which stars cannot construct. This means that the components of your body are truly ancient: you are stardust.
10. The quantum body
One of the mysteries of science is how something as apparently solid and straightforward as your body can be made of strangely behaving quantum particles such as atoms and their constituents. If you ask most people to draw a picture of one of the atoms in their bodies, they will produce something like a miniature solar system, with a nucleus as the sun and electrons whizzing round like planets. This was, indeed, an early model of the atom, but it was realized that such atoms would collapse in an instant. This is because electrons have an electrical charge and accelerating a charged particle, which is necessary to keep it in orbit, would make it give off energy in the form of light, leaving the electron spiraling into the nucleus.