Michio Kaku Says We're Probably Not in a Simulation, and He Has 71 Years of Physics to Back It Up

Michio Kaku has been thinking about the universe since he was 8 years old, when he read a newspaper story about a dead scientist who had failed to find the final theory of everything. That scientist turned out to be Einstein. Kaku decided, right then, that he wanted to finish the job. Seventy-one years later, he’s on Diary of a CEO, explaining black holes with a bag of marbles, and it is genuinely wonderful.

Host Steven Bartlett asks the questions your curious but non-physicist friend would ask, and Kaku fields every one of them with the patient precision of someone who has explained the Large Hadron Collider to a lot of nervous interviewers. What is the Big Bang? What’s inside a black hole? Could we be living in a simulation? The answers range from thrilling to humbling to, in one case, a flat dismissal that lands harder than any elaborate rebuttal could.

Everything Is a Vibrating String, and Yes, That Includes You

The string theory explanation is the kind of thing that sounds like metaphor but is not. Kaku co-founded string field theory, which holds that electrons, protons, neutrons, all the subatomic particles we’ve spent billions of dollars smashing apart in Geneva and outside Chicago, are not actually different things. They’re the same thing doing different things. One string, vibrating in different modes.

How could mother nature be so malicious to create a universe at the fundamental level based on hundreds of different kinds of strings vibrating in different directions? Well, it’s really just one string.

The visual he builds is elegant: a single violin string producing different notes. Each note is a particle. The whole orchestra of matter, from the hydrogen in stars to the uranium in weapons, is one instrument. That’s a beautiful idea, and Kaku clearly still loves it the way you love a thing you’ve spent your whole life on.

Dark matter gets the same treatment. Kaku suggests it might just be the next octave of string vibration, matter vibrating at a frequency that doesn’t interact with light and so remains invisible. A Nobel Prize is sitting there unclaimed for whoever proves it. He says this not as a tease but as a genuine invitation.

The Simulation Theory Takedown Is Mercifully Quick

Bartlett raises Nick Bostrom’s simulation argument with the confidence of someone who heard it at a dinner party and found it persuasive. Kaku hears it out. Then he adds a fourth option Bostrom never offered.

Option four is that there is no simulation at all, that all this talk is nothing but fairy tales. Fairy tales that we tell our children to amaze them about the universe.

His actual objection is more rigorous than the line suggests. Quantum theory, which predicts atomic and chemical probabilities with staggering accuracy, has no room for the deterministic script that simulation theory requires. A simulation needs a programmer pulling strings. Quantum mechanics is strings with no one pulling them. The two frameworks are incompatible, and Kaku, who has spent his career working in one of them, finds the other one frankly unserious.

There’s something refreshing about a physicist who will just say no to a fashionable idea. Elon Musk thinks we’re almost certainly in a simulation. Michio Kaku, who helped build the theoretical foundation for understanding what reality actually is, thinks that’s a fairy tale. Choose your corner.

The Black Hole as Gateway

The most imaginative moment in the episode is Kaku on black holes, and specifically on what might be inside them. He’s careful to flag it as speculation, but he lets himself go.

If I were to take a guess, I would say that it’s an entrance. It’s a gateway perhaps to another universe.

He explains the event horizon, the point of no return where escape velocity equals the speed of light, with a clarity that makes the abstract feel physical. You can almost feel the pull. The wormhole as shortcut to Alpha Centauri follows naturally, and for a moment the conversation feels less like a science podcast and more like a Jules Verne novel that happens to be mathematically defensible.

Kaku started this work because an 8-year-old saw a newspaper story about a man who died trying to understand everything. He’s now 79, still running Einstein’s equations, still not finished. The universe keeps expanding. So does the theory.