the end of the world

Light theme in these dark days: Apocalypse.

My favorite definition of (natural) science is the answer to the question: What happens next? From weather reports to RIVM forecasts, we see how science attempts to predict the near future based on knowledge of the present.

The existence of such a crystal ball is a hard-earned idea. Perhaps the greatest scientific discovery of all was the idea of ​​natural laws by Galileo, Newton, and others in the seventeenth century. Fixed rules molded into mathematical formulas that reality must strictly adhere to. Unlike traffic or tax laws, natural laws don’t have loopholes that an easy type can slip through.

Thus, science has become a large prediction machine with inputs and outputs. You enter the current state of the world, turn the sports gear knob and the answer appears: the state after a while. No need for outside interventions, just a matter of accurate calculation. Over the centuries, the machine metaphor has shifted from a mechanical clock mechanism to an electronic computer to artificial intelligence – we live in a simulation! – But the inevitable worldview remained.

The machine explodes

But does this prediction machine work in all circumstances? Not every input gives a legitimate output automatically. The existence of natural laws does not preclude the possibility of a “singularity”, a solution that loses meaning at some point, for example because a variable becomes infinitely large. There may be an initial case where the machine “explodes” trying to predict the future.

For example, Newton’s laws of celestial mechanics essentially allow a planet to be pushed into the farthest corner of the universe. The issue of the stability of the solar system was an existential problem in the nineteenth century. Regardless of the practical concerns of such a planetary launch, it would mean the collapse of science itself. Time to study the machine manual.

The solution came from the French mathematician Henri Poincaré. In 1890 he showed that the answer depends critically on the details of the initial state. In general, the solar system is stable – which is very reassuring – but it is not so in exceptional circumstances. His work is now seen as the birth of chaos theory.

The discovery of the atom at the beginning of the twentieth century brought another potential catastrophe, now in the microcosm. This time the stability of the matter was called into question. The atoms were then envisioned as miniature solar systems in which electrons orbited around a nucleus. Since these particles are electrically charged, they lose energy through radiation and then collide with the nucleus.

The same dilemma arose on a larger scale. A piece of matter, eg the chair you’re sitting in, is easily made up of a trillion times a trillion atoms. This is a huge group of negatively charged electrons and a positively charged atomic nucleus, which attract each other and repel each other via electric forces. Why don’t all these particles clump together in a big pile and destroy all the same matter in a gigantic explosion? How can you sit quietly on such an atomic house of cards?

In the end, quantum theory provided the solution. An improved system of the laws of nature – for example, a glass sphere 2.0 – explicitly prevents particles from falling into each other’s arms via the so-called Pauli principle, discovered by Austrian physicist Wolfgang Pauli. Only in this way can we understand why matter is stable and things are as big as they are.

happy bunch

Are we finally free of singularities? Is the prediction machine running smoothly now? Unfortunately, there is one last disaster to worry about. The empty space itself turned out to be untrustworthy. Vacuum is one of the most exciting things in modern physics and it is not empty. Quantum theory has a policy of tolerance that allows all kinds of processes if they happen fast enough before they can be observed. This makes the empty space a playful mess in which the smallest particles secretly play tricks. There is a possibility that this virtual card house is a “pseudo” space. The details depend on the exact properties of the particles that we know only in part.

At some point, nature may realize that things are not what they seem and still move into the “real” void. The word “singularity” hardly does justice to the enormity of that drama. This apocalypse is nothing short of the end of reality. A new world will take shape. No form of matter, not even space and time, will survive this transition.

There is little consolation. Even in the worst case scenario, the apocalypse will take some time. Soon it’s a googol year, 1 has a hundred zeros.

Until then, we have other concerns.

Robert Decgrave Director of the Institute for Advanced Study at Princeton.