If you hold your breath for too long, you will die. Your body needs the oxygen in the air. Without getting enough oxygen, you can’t survive. That’s why divers always take bottles of oxygen with them. After all, under water there is no air to breathe.

At the ALMA observatory, it’s hard to breathe normally. The 66 ALMA antennas are located at the Chajnantor Plateau, at five kilometers above sea level. At that altitude, the air is very thin. That’s good for observing millimeter waves from the Universe. But it’s bad for humans. There’s only half the normal amount of oxygen.

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Strange things can happen to you if your body doesn’t get enough oxygen. First of all, you get tired really soon. Even walking for a hundred meters or so is exhaustive. And it’s downright impossible to run, or to carry heavy things around.

Rapidly kneeling down, standing up or just quickly turning your head makes you feel dizzy. You get terrible headaches. You feel nauseous, and if you’re unlucky, you have to vomit. Moreover, it’s hard to concentrate on anything. You can’t think clear, your handwriting turns into a crazy scribble, and you start to speak gibberish. All because of the lack of oxygen.

And there are other hardships at Chajnantor. Because it is so high, it is usually very cold. Sometimes the temperature is well below zero. The wind can be extremely strong. And since there is almost no atmosphere to protect you, you risk a terrible sunburn.

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Little wonder than that no one lives at the Chajnantor Plateau. Of course, sometimes engineers and technicians need to be there. But at the end of the day, everyone leaves again. During the night, the ALMA antennas are alone with the stars.

So where do the ALMA astronomers live? They stay at the ALMA base camp. It’s officially known as the OSF – the Operations Support Facility. And it’s at an altitude of some 2,900 meters, so there’s enough oxygen to breathe. Pretty soon, there will be a real hotel for everybody there.

The control room of the ALMA observatory is also at the OSF. Moreover, there are offices, workshops, laboratories and a restaurant. It’s also the place where the ALMA antennas have been constructed before they were taken to the Chajnantor Plateau.

But you know what? Astronomers who observe with ALMA just stay at home. They don’t travel all the way to Chile. They receive the results of their observations through email!