Sabine Hossenfelder, physicist: ‘If you trust the mathematics, we are immortal’

Is there anything after death? What is the meaning of life? Are we just a bag of atoms? The scientist Sabine Hossenfelder, born in Frankfurt (Germany) 48 years ago, is convinced that if there is a branch of science capable of finding answers to humanity’s existential questions, it is physics. Specialized in theoretical physics and quantum gravity, Hossenfelder combines her research work with science communication (she is the creator of the YouTube channel Science without the gobbledygook). Her latest book, Existential Physics: A Scientist’s Guide to Life’s Biggest Questions (published in English in 2022, and out in Spanish this year) is aimed at “those who have not forgotten to ask the big questions and are not afraid of the answers.”

Question. You ask all the relevant people in science that you interview if they are religious. You define yourself as pagan and agnostic, but you always create a bridge between science and religion, so I will follow your lead and ask: are you religious?

Answer. No. But I do believe that human consciousness – and complexity in general – is more closely intertwined with the universe in its entirety than we currently appreciate. That is, while I do not sign up to any recognized religion, I too have beliefs that are not based on evidence.

Q. You claim that a person’s information, if we trust mathematics, is still there after death, dispersed throughout the universe, forever. Are we immortal?

A. If you trust the mathematics, yes. But it is not an immortality in the sense that after death you will wake up sitting in hell or heaven, both of which – let’s be honest – are very earthly ideas. It is more that, since the information about you cannot be destroyed, it is in principle possible that a higher being someday, somehow re-assembles you and brings you back to life. And since you would have no memory of the time passing in between – which could be 10¹⁰⁰ billion years! – you would just find yourself in the very far future.

Q. In the same sense, you affirm that our existence transcends time: “We have always been and will always be children of the universe,” you write. Does it mean that life and after it there is a permanent link to the universal system as long as it exists?

A. Yes. Think of death as a drop of ink that falls into the ocean. You are the drop, the ocean is the universe. That what made up the drop (you) will spread in the ocean (universe) and become unrecognizable. But it never disappears.

Think of death as a drop of ink that falls into the ocean. You are the drop, the ocean is the universe. That what made up the drop (you) will spread in the ocean (universe) and become unrecognizable. But it never disappears.

Q. If all theories about the origin of the universe are “pure speculation,” should I rule out the idea of the Big Bang?

A. The Big Bang is currently the simplest of our theories about the beginning of the universe. That makes it the hardest to dismiss. But that doesn’t mean it is correct. Maybe the true story is more complicated than that. Our current observations can’t tell us. I would say that the Big Bang is, at the moment, scientifically the most pragmatic explanation, but I think it is scientifically justifiable that you believe in something else, like a cyclic universe.

Q. Do we die because of increasing entropy, disorder, or uncertainty in a system? Do we live because of anti-entropy?

A. You can ask about the causes of death on many levels of explanation. A doctor might give you an explanation on the level of organ failure. A neurobiologist might give you an explanation based on the cell processes that contribute to aging. As a physicist I would say that what ultimately kills us is our inability to keep up order, hence, it is entropy increase. Anti-entropy is not a term that we use in physics, but you could loosely speaking identify it with free energy. Free energy is what it takes to decrease entropy. Our body’s main source of free energy is food. We use it to move and to maintain the functions of our organs, as long as we can. But errors build up inevitably, and eventually our bodies have a malfunction that we cannot repair. It is possible that in the future we get vastly better at repairing our bodies and will live much longer. And yet, entropy increase would still get us eventually because it will ultimately make life impossible in the entire universe.

The Big Bang is currently the simplest of our theories about the beginning of the universe. That makes it the hardest to dismiss. But that doesn’t mean it’s correct

Q. You write that the future is fixed, except for occasional quantum events that we cannot influence. What quantum events?

A. By “quantum event” I here mean any event whose outcome is not pre-determined. This is the most distinct feature of quantum mechanics, that the outcomes of some events are impossible to predict. This might for example be UV radiation hitting a cell in your skin. Will it, or will it not, cause sufficient damage to create a cancerous mutation that will kill you five years down the line? We can only predict the probability of it happening, but we cannot predict with certainty what will happen.

Q. Your book begins with a student's question about his grandmother's theory that we survive in a quantum system. Since humans are basically composed of 10 chemical elements, can their particles transcend biological death?

A. The chemical elements will survive for a long time, and after that there are still the subatomic particles that they are made of. The answer to the question depends on what you make of the measurement problem in quantum mechanics. Is it possible that someone (or something?) measures the entire universe? If you think so, information inside of the universe can get lost for good. But I think it’s not possible – who would do the measuring? This is why I think information inside the universe is forever preserved – and so is your dead grandmother.

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