What happened in this episode?
Prof Brian Greene, a theoretical physicist at Columbia University and a leading public communicator of cosmology, discusses with Steven Bartlett how modern physics frames “the true nature of reality”. Greene describes string theory as a mathematical proposal that fundamental particles are vibrating filaments, while stressing it remains unconfirmed because today’s experiments cannot probe that scale. The conversation moves into philosophical territory, including the simulation argument: Greene says it is logically possible the world is simulated but that he sets the idea aside because it undercuts reasoning itself.
On AI, Greene reports that some researchers he has spoken to think today’s large language models are conscious, though he rejects that view for current systems and says they may only simulate feelings. He nonetheless argues consciousness is a physical process and sees no fundamental barrier to conscious machines, raising the prospect of future debates about robot rights and the difficulty of proving sentience. Greene warns that AI capability could grow faster than society can respond, and he expresses concern about the concentration of AI power in a small number of firms.
Greene also takes firm positions on long-running human questions. He says he has “high confidence” humans lack free will, portraying choices as the lawful unfolding of physics. On religion, he calls an anthropomorphic God a human creation and suggests religions largely function to manage existential anxiety about death. The episode also covers extraterrestrial life, time dilation, and long-term cosmological forecasts about the universe’s far future, alongside Greene’s personal veganism and ethics.
