## Pages

### Physics rules out the presence of "Soul", "Ghosts", and "Afterlife"

Brian Cox and Sean Carroll have dissected the concepts of soul, ghosts and afterlife.

Short story: Physics rules out the presence of "soul", "ghosts", and "afterlife".

Reason in brief: If the soul has to be present and driving our body functions, it has to be interacting strongly with matter, which our bodies are made of. We know very well, to a high degree of precision, how the particles of matter behave, which our bodies are made of, at the energies of room temperature. This knowledge rules out the presence of any other 5th force that interacts with matter at these energies.  A similar argument can be extended to ghosts and by extension afterlife is ruled out.

## Sean Carroll

"Claims that some form of consciousness persists after our bodies die and decay into their constituent atoms face one huge, insuperable obstacle: the laws of physics underlying everyday life are completely understood, and there’s no way within those laws to allow for the information stored in our brains to persist after we die. If you claim that some form of soul persists beyond death, what particles is that soul made of? What forces are holding it together? How does it interact with ordinary matter?
Everything we know about quantum field theory (QFT) says that there aren’t any sensible answers to these questions. Of course, everything we know about quantum field theory could be wrong. Also, the Moon could be made of green cheese.
Among advocates for life after death, nobody even tries to sit down and do the hard work of explaining how the basic physics of atoms and electrons would have to be altered in order for this to be true. If we tried, the fundamental absurdity of the task would quickly become evident.
Even if you don’t believe that human beings are “simply” collections of atoms evolving and interacting according to rules laid down in the Standard Model of particle physics, most people would grudgingly admit that atoms are part of who we are. If it’s really nothing but atoms and the known forces, there is clearly no way for the soul to survive death. Believing in life after death, to put it mildly, requires physics beyond the Standard Model. Most importantly, we need some way for that “new physics” to interact with the atoms that we do have.
Very roughly speaking, when most people think about an immaterial soul that persists after death, they have in mind some sort of blob of spirit energy that takes up residence near our brain, and drives around our body like a soccer mom driving an SUV. The questions are these: what form does that spirit energy take, and how does it interact with our ordinary atoms? Not only is new physics required, but dramatically new physics. Within QFT, there can’t be a new collection of “spirit particles” and “spirit forces” that interact with our regular atoms, because we would have detected them in existing experiments. Ockham’s razor is not on your side here, since you have to posit a completely new realm of reality obeying very different rules than the ones we know.
But let’s say you do that. How is the spirit energy supposed to interact with us? Here is the equation that tells us how electrons behave in the everyday world:
$i\gamma^\mu \partial_\mu \psi_e - m \psi_e = ie\gamma^\mu A_\mu \psi_e - \gamma^\mu\omega_\mu \psi_e .$
Dont’ worry about the details; it’s the fact that the equation exists that matters, not its particular form. It’s the Dirac equation — the two terms on the left are roughly the velocity of the electron and its inertia — coupled to electromagnetism and gravity, the two terms on the right.
As far as every experiment ever done is concerned, this equation is the correct description of how electrons behave at everyday energies. It’s not a complete description; we haven’t included the weak nuclear force, or couplings to hypothetical particles like the Higgs boson. But that’s okay, since those are only important at high energies and/or short distances, very far from the regime of relevance to the human brain.
If you believe in an immaterial soul that interacts with our bodies, you need to believe that this equation is not right, even at everyday energies. There needs to be a new term (at minimum) on the right, representing how the soul interacts with electrons. (If that term doesn’t exist, electrons will just go on their way as if there weren’t any soul at all, and then what’s the point?) So any respectable scientist who took this idea seriously would be asking — what form does that interaction take? Is it local in spacetime? Does the soul respect gauge invariance and Lorentz invariance? Does the soul have a Hamiltonian? Do the interactions preserve unitarity and conservation of information?
Nobody ever asks these questions out loud, possibly because of how silly they sound. Once you start asking them, the choice you are faced with becomes clear: either overthrow everything we think we have learned about modern physics, or distrust the stew of religious accounts/unreliable testimony/wishful thinking that makes people believe in the possibility of life after death. It’s not a difficult decision, as scientific theory-choice goes.
We don’t choose theories in a vacuum. We are allowed — indeed, required — to ask how claims about how the world works fit in with other things we know about how the world works. I’ve been talking here like a particle physicist, but there’s an analogous line of reasoning that would come from evolutionary biology. Presumably amino acids and proteins don’t have souls that persist after death. What about viruses or bacteria? Where upon the chain of evolution from our monocellular ancestors to today did organisms stop being described purely as atoms interacting through gravity and electromagnetism, and develop an immaterial immortal soul?
There’s no reason to be agnostic about ideas that are dramatically incompatible with everything we know about modern science. Once we get over any reluctance to face reality on this issue, we can get down to the much more interesting questions of how human beings and consciousness really work."

## Brian Cox

[Following is the transcript of the video. I recommend watching the video for better comprehension]

"So, here is my arm. It is made of electrons and protons and neutrons. If I have a soul in there, something we don't understand - different kind of energy or whatever it is. We don't have physics at the moment. It interacts with the matter because I am moving my hand around. So, whatever it is, it is something that interacts very strongly with matter. But, if you look at the history of particle physics in particular, which is the study of matter, we spent decades making high precision measurements of how masses behaves and interacts. And we look for example, for the fifth force of nature. We know four forces - gravity, two nuclear forces called weak and strong nuclear forces and electromagnetism. And that's what we know exists. we looked for another one with ultra-high precision and we don't see any evidence of it. So, I would claim that we know how matter interacts at these energies at room temperature. We know how matter interacts very precisely.

If we want to suggest that something else that interacts with matter strongly, then I would say that it's ruled out, I would go as far as saying that it is ruled out by experiment. It is extremely subtle and you would have to jump a lot of hoops to come up with a theory of some stuff that we wouldn't have seen when we observed how it interacts it with matter that is present in our bodies. Presumably, we believe in the soul that we wanted to exist outside, when you die, you might believe in ghosts and things like that.

If ghosts are something that carries the imprint of you presumably, it looks like you. So, that means that it interacts strongly with the matter that is you. Because it carries a pattern. If it carries a pattern, it carries information. If it carries information, there has to be an energy source to allow for that information and pattern to persist. Again, you end up with a theory that is postulating something that interacts with light. If you think a ghost is a soul, then it is something that people see sometimes. That means it interacts with light. But we know how light interacts."