StarTalk Radio – "Your Brain is a Time Machine"
Host: Neil deGrasse Tyson
Guest: Dean Buonomano (Professor of Neurobiology and Psychology, UCLA; Author of Your Brain Is a Time Machine)
Co-hosts: Gary O’Reilly, Chuck Nice
Date: January 9, 2026
Episode Overview
This StarTalk Special Edition brings together astrophysicist Neil deGrasse Tyson, comedian Chuck Nice, and commentator Gary O’Reilly with guest neuroscientist Dean Buonomano to explore the intersections between neuroscience and physics through the grand question: Is the brain the universe’s only real time machine? The conversation traverses how we perceive, measure, and remember time—from the molecular to the philosophical, from circadian clocks to time travel in dreams and science fiction. Through humor, tangible science, and insightful analogies, the episode investigates the profound mysteries of how and why humans experience time.
Key Discussion Points & Insights
1. How Do Brains Tell Time?
- Comparing Clocks & Brains:
Man-made clocks rely on regular, repeating oscillations to measure time (e.g., pendulums, atomic vibrations), whereas the brain is a complex dynamical system without a single, dedicated "clock.""The brain does not work like that. … The clocks in our brain that are responsible for seconds, they don’t have an hour hand, and the circadian clock doesn’t have a second hand."
—Dean Buonomano [06:16] - Neural Dynamics as Timing:
Instead of regular oscillators, brains employ evolving patterns of neural activity, analogous to an hourglass’s flow rather than a ticking pendulum."The brain is the most complex dynamical system we know of. … Patterns of activity are what we use to tell time on the timescale of seconds."
—Dean Buonomano [07:06]
2. Biological Timekeeping—Circadian Rhythm
- The master clock in mammals is the suprachiasmatic nucleus, reliant on light signals for synchronizing the body’s rhythms with Earth’s 24-hour cycle.
- Experiments in Circadian Biology:
Dean describes work with cyanobacteria, showing that survival depends on matching internal clocks to external cycles."You need to tell time in order to engage the body, the proteins and the brain to anticipate changes in our environment. And that’s extraordinarily valuable."
—Dean Buonomano [11:24]
3. Why Has Humanity Always Cared About Telling Time?
- Societal advances—from the Industrial Revolution to collective work—depend on synchronizing human behavior through standardized clocks.
- Galileo's Discovery:
Galileo observed a swinging chandelier matched to his pulse, leading to the use of pendulums in clocks."He concluded that a pendulum, within limits … has the same period. You can put pendula in clocks and that's a sort of self-regulating mechanism."
—Neil deGrasse Tyson [13:32] - Factory Synchronization:
Cheap, reliable clocks enabled mass labor to occur on schedule—a root driver behind the Industrial Revolution.
4. Sensing Time Without Clocks
- Animals (including early humans) possess innate timing abilities, crucial for survival and social interaction.
- Language Is Temporal:
Meaning can change with timing and pauses, e.g., "They gave her cat food" vs. "They gave her cat food.""That timing is always going on. … It's totally unconscious."
—Dean Buonomano [21:55]
5. Is the Flow of Time Real? Physics vs. Neuroscience
- Physics suggests time could be an illusion—past, present, future all equally real (Eternalism), yet neuroscience leans on the subjective flow of time as a byproduct of conscious evolution.
"I've argued … the brain is telling us something true about the physical universe … we evolved to survive in a universe governed by the laws of physics in a mesoscopic part of that universe. … Our brain creates this conscious perception of the flow because it's a real part of what we experience and the universe."
—Dean Buonomano [24:54] - Arrow of Time:
The persistent sense of moving from past to future underpins our sense of mortality and anticipation. - Mesoscopic Scale:
Human perception is tailored to the “middle” scale of the universe—neither quantum nor cosmic.
6. Mental Time Travel—Memory and Imagination
- Humans uniquely project themselves backwards (memory) and forwards (imagination/future planning).
"This ability to jump, make these cognitive leaps across time, is an incredibly sophisticated thing we do, but we're still not very good at it. … I think about the first ancestors that had that ability to look into the future … 'Oh shit, I'm going to die.'"
—Dean Buonomano [27:54] - Dreams as Time Machines:
Perceived time dilates in dreams—a phenomenon mused on via references to Inception and Rick and Morty. - Animals and Future Planning:
Instinctual behaviors like squirrels storing food are evolutionarily programmed, not conscious future projection.
7. How Are Memories Stored in the Brain?
- Unlike a computer, brain “memory” is stored in the changing strengths of synaptic connections (Hebbian plasticity), entwining computation and storage.
"It’s extraordinarily hard to separate those two things in the case of human memory."
—Dean Buonomano [31:46] - Dynamical Memory:
The brain uses processes like sequences and patterns of activation, not simple storage “locations.”
8. Integrating the Senses—Temporal Windows
- The brain automatically synchronizes disparate sensory inputs (sight and sound) within adaptive “windows of integration,” elegantly editing reality for us.
"So in that sense, it's just your brain being flexible and sort of trying to align time and space. The brain fixes it for you, like magical."
—Dean Buonomano [41:13] - Illustrated by Film Jokes:
Joking about poor lip-sync in old martial arts movies as a scenario where the illusion breaks down."We're all in one big kung fu theater movie from old school Saturday afternoon."
—Chuck Nice [42:46]
9. Physics: Relativity vs. Neurological Time
- Special and General Relativity can bend and warp time for different observers, but for any individual, subjective time always flows at a constant rate; you can only perceive discrepancies when comparing clocks.
"In neuroscience, it never slows down for you. You just always have your time, and it's all happening to everybody else, and you only know it's happening … because you're measuring it."
—Neil deGrasse Tyson [43:21]
10. Science Fiction: Implants, Memory Uploading, and Time Travel
- Science fiction loves brain-computer interfaces and memory implantation (e.g., Total Recall, Matrix, Black Mirror), but the reality is far messier:
"People have the idea that, yes, if we have all these wires into my brain and they're hooked up to a computer … I'll be able to speak Mandarin, or I'll be able to fly a plane. I don't think that's going to happen."
—Dean Buonomano [47:03] - The brain lacks the clear, modular architecture of a computer—uploading skills or memories is currently not possible.
11. Is Mental Time Travel the Only Kind Possible?
- Dean's stance: The only real time machine permitted by physics is the mind, through memory and imagination.
"The closest we'll ever get to a time machine is our mental time travel. … Actual time travel is a theoretical impossibility."
—Dean Buonomano [49:09] - Aligns with Stephen Hawking’s humorous "time travel prevention conjecture."
12. Limits of Human Understanding
- The human brain is studying itself—a recursive, possibly unsolvable task.
"Neuroscience is the most recursive field in science … there's reasons to think it gives me job security. … There may be reasons to believe that no system is capable of understanding itself."
—Dean Buonomano [51:04] - Mathematics is our "debugging" tool for the limitations of intuition and cognitive bugs.
"The greatest debugging device we ever invented is called mathematics, because mathematics allows us to simulate, to model, to capture things we don't understand."
—Dean Buonomano [52:02] - "Shut up and calculate," the classic physicist motto, pops up here.
Notable Quotes & Memorable Moments
-
On Brain Storage:
“In a computer memory, there’s a very clear dichotomy between the memory and the computations being performed. In the brain, that distinction doesn’t make as much sense … it’s extraordinarily hard to separate those two things.”
—Dean Buonomano [30:35] -
On Mental Time Travel:
"Humans have been known to engage in future-oriented activities without necessarily thinking what will happen nine months into the future."
—Dean Buonomano [29:39]
"That's called screwing." —Chuck Nice [29:50] -
On the Limitations of the Brain:
“Do we understand quantum mechanics? I don’t. … The greatest debugging device we ever invented is called mathematics.”
—Dean Buonomano [51:58-52:02] -
On Time and Human Experience:
“The clocks in our brain that are responsible for seconds, they don’t have an hour hand, and the circadian clock doesn’t have a second hand. This is fundamentally different from how our man-made clocks are working.”
—Dean Buonomano [06:16] -
On Sci-Fi Tech (Matrix/Total Recall):
"I’m very skeptical of those notions because I think they don’t really capture how the brain actually works."
—Dean Buonomano [47:03] -
On Human Cognitive Evolution:
“Can you imagine what it was like for the first human to make this cognitive leap and say, ‘Oh shit, I’m going to die.’”
—Dean Buonomano [27:54] -
On Evolution and Religion:
“There was a co-evolution between our ability to engage in mental time travel and religion, because religion was the antidote to this vision that we saw that we were going to die.”
—Dean Buonomano [28:21] -
On Human Stupidity:
"There's this debate in AI whether AI is as smart as human beings, but … human beings are a pretty low bar."
—Dean Buonomano [52:49]
"Exactly. I'm with you 100%." —Chuck Nice
Timeline of Noteworthy Segments
- 04:25 – What distinguishes biological clocks from man-made clocks
- 07:51 – How circadian rhythms are molecularly mediated in the brain
- 13:09–15:21 – Synchronizing society: Why humanity needed precise clocks
- 21:52 – Timing in language and its unconscious processing
- 24:54–26:02 – Physics vs. neuroscience: Is the flow of time real?
- 27:10–29:01 – Mental time travel, death, and the origins of religion
- 31:46 – How synaptic changes equal memories
- 41:13 – The brain's "editing" of synchronized sensory input
- 43:13 – General relativity and subjective time
- 47:03 – The limits of brain-computer interfacing and sci-fi
- 49:09 – Brains as the only real time machines
- 51:04 – Can the brain understand itself (and the universe)?
Final Takeaways
- The human brain constructs a flowing present out of dynamic, ever-changing neural networks—blending memory, prediction, and perception in a tapestry that no man-made clock can match.
- Our mental leaps through time are as close as physics will allow to a real time machine—at least, according to current science.
- Intuition falters at the extremes (quantum mechanics, relativity, "block universe" time); mathematics and collective inquiry are our tools for peeling back deeper truths.
- Understanding the universe—and ourselves—is likely a perpetual challenge, perhaps one beyond our fully grasp.
Book Recommendation:
Your Brain Is a Time Machine: The Neuroscience and Physics of Time by Dean Buonomano (2017)
Closing Thought:
"Keep looking up." — Neil deGrasse Tyson