Ask A Genius 1283: Landauer Limit
Author(s): Rick Rosner and Scott Douglas Jacobsen
Publication (Outlet/Website): Ask A Genius
Publication Date (yyyy/mm/dd): 2025/03/01
Rick Rosner: A simple reason to suppose that an action potential is not the atomic action of cognition is that biological systems evolve toward the thermodynamic limit of sensitivity across every domain. And an action potential is a million times larger than the Landauer limit.
Scott Douglas Jacobsen: That’s the thermodynamic lower theoretical limit of energy consumption in computation. It states that any irreversible change in stored information dissipates a minimum amount of heat into its surroundings.
Rosner: So, you flip the state of a zero-one bit, or perform a basic computational function. In that case, there’s a minimum theoretical amount of energy that has to be spent. It’s tiny.
But an action potential in the brain—a neuron firing—releases a million times that energy.
This suggests that the minimum unit of computation isn’t a neuron firing because a neuron firing dissipates way more energy than the theoretical minimum needed to process information.
That makes me think that while neurons firing power the system of thinking, the thinking itself isn’t necessarily atomic in that way.
It’s not just flipping bits.
The mental landscape shifts with dendrites strengthening or weakening, which happens constantly. Maybe neurons firing is like… I don’t know. Maybe it takes a lot of shit to bring a neuron to the point of firing, but maybe that’s just a side effect of thinking.
Like a combustion engine. Your car runs on a series of tiny explosions in a normal combustion engine. Bam. Bam. Bam. Each piston compresses gas, ignites, and moves the next piston. But when you drive, you don’t feel those explosions as separate bursts of movement—it translates into smooth motion.
So neurons firing is like that. Maybe it’s part of the thinking process, but the thinking itself isn’t just neurons flipping between “on” and “off” states.
Neurons firing are just the background propulsion, while dendrites reshaping the mental landscape do the real work.
Maybe the neurons are just the flash bulbs that light up the landscape—but it’s the landscape that actually matters.
Not totally sold on the theory, but it’s intriguing. There are a lot of subtle ideas out there. Still, with something as complex as the brain—so new in evolutionary terms—many of these effects are probably just residual.
Like, they’re not primary functions, just leftover byproducts of the main system.
Still, I was surprised to learn that an action potential releases a million times more energy than the minimum needed for computation. That suggests there’s a whole fuck-ton of other shit going on beyond just neurons firing.
That’s safe to say.
What about glial cells? Aren’t they actually more prevalent than neurons?
We always talk about how much we don’t know about the brain. Still, at least 80% of the 86 billion neurons in an average brain are cerebellar neurons—motor neurons, basically.
Jacobsen: Yeah. Much of what we consider “higher cognition” isn’t what most of the brain is hooked up to do. Most of the brain is about language and movement.
Rosner: Which makes sense. According to standard theory, the brain exists to help you get out of trouble. You gotta move to survive. I don’t know—if you think about life 100,000 years ago, movement was probably everything.
And then there’s language, which makes thinking itself way more efficient.
If you’re out on the savanna 100,000 years ago, and you’ve somehow learned that moss only grows on the shady side of tree trunks and rocks… Without language, that’s hard to store in your head. And really hard to pass on to others.
With language?
I just did it in a sentence.
So, I get why language gets a huge chunk of the brain’s resources.
Also, I don’t think the savanna had a lot of moss on tree trunks. That’s more of a northern forest thing.
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