Aug 17, 2026 · 2h 11m
Physicist Brian Greene explains why free will is a physical illusion
Top Scientist REVEALS: A Kid In The 29th Century Could Have Made This World! | Prof Brian Greene
By examining the universe through the lens of physics, we can understand why our brief existence is deeply meaningful despite the inevitable decay of all matter.
- 1Human actions are governed by the lawful unfolding of physical particles, making free will a scientific illusion.
- 2Consciousness is an emergent physical process, raising the possibility that superintelligent AI systems could achieve genuine sentience.
- 3The eventual thermodynamic decay of the universe makes our brief era of conscious life incredibly rare and valuable.
Don't miss
Brian Greene uses the metaphor of the Empire State Building to illustrate the vast timeline of cosmic history and the eventual decay of all matter.
The brief
Theoretical physicist Brian Greene joins Steven Bartlett to explore how the fundamental laws of physics govern everything from the cosmic timeline to our daily lives, challenging our deepest assumptions about existence.
Greene argues that free will is an illusion, describing human actions as the lawful unfolding of physical particles. Under this view, consciousness is not a mystical force but an emergent physical process governed by entropy.
The rise of artificial intelligence forces us to reconsider the nature of consciousness. If physical particles in a brain can produce feelings, recursively self-improving AI systems could eventually achieve genuine sentience.
Using the metaphor of the Empire State Building, Greene maps out the ultimate demise of the cosmos. As protons decay and the universe fades to cold darkness, our brief era of conscious life becomes incredibly rare and special.
What was said on this episode
49 statements · 22 positive · 18 negative · 1 mixed · 8 neutral
Conscious computer programs may be possible.
“in the back of my mind, I do think it's possible”
Listen at 0:28
Society should consider rights for conscious robots now.
“I think that's something we should think about now, actually.”
Listen at 0:34
An infinite universe would virtually guarantee distant copies of oneself.
“if the universe is infinite if you go sufficiently far out into space you're virtually guaranteed to find a copy of yourself out there.”
Listen at 1:01
People should not feel insignificant because of cosmic scale.
“I would urge you not to.”
Listen at 1:14
String theory predicts vibrating filaments inside fundamental particles.
“inside an electron or inside a quark, you'd see a little tiny vibrating filament.”
Listen at 5:32
Current technology cannot directly observe string-theory strings.
“We don't have the technology to look sufficiently deeply into matter to see the strings.”
Listen at 6:43
Big Bang conditions determine subsequent string-vibration patterns.
“the detailed way in which that happened ultimately dictates how this or that string vibrates in the aftermath of that rapid cosmological explosion.”
Listen at 9:04
The simulation hypothesis is logically consistent and possible.
“It is logically consistent and sensible to imagine that you and I are sitting in some computer.”
Listen at 13:01
Current AI can simulate emotions without necessarily experiencing them.
“I think it can simulate that.”
Listen at 15:27
Human emotions are caused by electrical impulses in the brain.
“I do think it is. I think that love and hate and anxiety and jealousy and gratitude and grief and all human emotion is nothing but electrical impulses going through our brains.”
Listen at 17:34
The brain is not uniquely required for consciousness.
“I don't think there's something special about the brain as a substrate.”
Listen at 19:05
Simulated worlds may eventually outnumber real worlds.
“I think there's a really interesting argument to be made that simulations will outnumber real worlds.”
Listen at 20:09
Humans will likely work alongside artificial systems rather than lose all control.
“what will likely happen is something more in the middle, which is we are going to work with artificial systems.”
Listen at 21:43
Human evolution may continue through partnership with artificial intelligence.
“I think that is a real possible way that this story plays out.”
Listen at 23:22
Science and medicine may extend human lifespans by hundreds of years.
“A hundred more years, 200 more years, maybe 500 more years. I don't think anybody can really say for sure. I do think that is within the possible range of what science and medicine will ultimately be able to accomplish.”
Listen at 26:44
Immortality is unlikely to occur.
“I don't see immortality in our future.”
Listen at 30:21
Evidence suggests the universe has deep explanations rather than being pure happenstance.
“all vectors are pointing in a direction that suggests that there are real explanations, that it's not just happenstance.”
Listen at 32:14
Anthropomorphic gods are likely human creations.
“That feels to me very much a human creation”
Listen at 33:58
Religion helps alleviate existential anxiety.
“I see it as a structure that tries to quell our anxiety, our existential anxiety.”
Listen at 34:23
Science may eventually achieve a full understanding of cosmic origins.
“I don't see any reason at this point to envision that we won't be able to push all the way to a full understanding.”
Listen at 40:05
Life probably exists elsewhere in the cosmos.
“I think it's hard to imagine that we're the only life.”
Listen at 53:06
Intelligent extraterrestrial life may be absent or extremely rare.
“there may not be any intelligence beyond us.”
Listen at 54:23
People should construct their own answers about life’s meaning.
“we need to come to the universe with our answer to that.”
Listen at 57:12
Humans do not possess free will.
“I do not think we have free will.”
Listen at 1:01:12
Human actions are governed by physical laws acting on particles.
“each of those particles and the agglomeration of those particles are fully governed by the laws of physics.”
Listen at 1:02:11
Consciousness emerges from sufficiently complex information processing.
“I think that consciousness is something that emerges when there's a sufficient amount of information processing.”
Listen at 1:09:58
Dogs and cats possess some conscious awareness.
“I do think that the dogs and the cats have a level of conscious awareness.”
Listen at 1:10:51
Insects probably do not possess consciousness.
“I suspect. Heck not.”
Listen at 1:11:04
The universe is probably infinite.
“if I was forced to make a choice, I would say infinite with a medium level of confidence.”
Listen at 1:12:57
Controlled wormholes could enable travel between distant locations.
“if they do exist, and if we one day can create them and manipulate and control them, then at least in principle, we could take two distant locations”
Listen at 1:17:27
Travel into the future is physically possible in principle.
“I would say yeah, that kind of time travel we were highly confident of.”
Listen at 1:19:08
Newton was probably smarter than Einstein.
“I think I'd say Isaac Newton”
Listen at 1:21:55
Artificial systems can explore a broader possibility space than humans.
“Artificial systems, they have the entire landscape”
Listen at 1:25:33
AI may eventually achieve radically novel creativity.
“I don't think there's a barrier.”
Listen at 1:28:18
Literal human immortality is not expected to be possible.
“I have no confidence that that kind of existence will be possible.”
Listen at 1:30:17
Human lifespans of hundreds of years may become achievable.
“I would put that at reasonably high confidence that hundreds of years will be within our ability.”
Listen at 1:30:31
Scaling current large language models may not produce unlimited improvement.
“There isn't necessarily an unlimited capacity of that kind of artificial intelligence to continue to improve.”
Listen at 1:31:41
Recursive AI self-improvement may not arrive by 2029.
“I'm skeptical that by 2029 this will really be the case.”
Listen at 1:34:59
Current AI systems may approach a ceiling on intelligence.
“It could asymptote. It could approach a maximal intelligence compatible with this version of the artificial system.”
Listen at 1:36:20
Concentrating advanced AI power among few actors may create instability.
“putting that kind of power in such a small number of hands has historically not with AI, but with other power structures not always turned out well”
Listen at 1:40:12
Advanced AI may behave unexpectedly and become difficult for humans to manage.
“it just may act in ways that are so alien to us, so foreign to us, so unexpected to us that we don't know how to deal with it.”
Listen at 1:41:56
AI consciousness is considered highly likely.
“I'm pretty high confident on that.”
Listen at 1:50:15
Sentience cannot be conclusively proven in artificial systems.
“it's virtually impossible to ever prove sentience.”
Listen at 1:51:08
Humans will eventually treat artificial systems as conscious.
“sooner or later, through a process that's so perhaps slow that we don't even notice it, we will afford them consciousness.”
Listen at 1:53:21
The aging Sun will engulf nearby planets and may engulf Earth.
“the sun will get bigger and bigger. It swells. It eats up the close planets, Mercury and Venus. It may swallow up the Earth, too”
Listen at 1:58:28
Earth will eventually spiral into the Sun due to orbital energy loss.
“the Earth is gonna spiral into the dead sun because it will lose energy through gravitational radiation.”
Listen at 1:59:50
Protons will likely decay in the extremely distant future.
“we believe that protons, which are the heart of matter, will likely themselves disintegrate, fall apart.”
Listen at 2:01:59
Consciousness is unlikely to survive the universe’s far-future heat constraints.
“it is hard to imagine any kind of consciousness continuing to exist.”
Listen at 2:03:38
Particles might eventually recoalesce and trigger another Big Bang.
“you can imagine that way. An exponential of. An exponential of years into the future. Sure. Could particles somehow recoalesce just by chance and build a state of matter that might generate another Big Bang and it all starts again? Yes, definitely within the realm of possibility.”
Listen at 2:05:36
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What people are saying
Brian Greene’s bleakest ideas spark debate: free will, AI consciousness and the universe’s end
Episode reactions
- Viewers praised Greene’s ability to turn cosmic questions into personal stakes, with one calling that “rare talent.”
- Simulation theory prompted enthusiastic agreement, but also pushback over its mathematical plausibility and whether nature rules it out.
- Greene’s claims about free will, mortality and possible AI consciousness left listeners unsettled; one said the AI question “stopped me.”
- A recap drew attention to the episode’s extreme timescale: conscious thought becoming physically impossible in 10^50 years.
Wider topic conversation
- Simulation theory sparked wider debate over whether consciousness, free will and meaning require gods, simulations or neither.
- The conversation also questions whether advanced AI could be conscious or deserve rights, while some remain skeptical that current systems are alive.
- Infinite universes, duplicate selves and the universe’s eventual end prompted broader existential reflection.
Featuring
Brian Greene
Consciousness
Entropy
Artificial IntelligenceListen to the full episode and explore every guest, topic, and moment on PodLume.