The primary challenge in robotics AI is the lack of real-world training data. To solve this, models are bootstrapped using a combination of learning from human lifestyle videos and extensive simulation environments. This creates a foundational model capable of initial deployment, which then generates a real-world data flywheel.

To build generalist robots, the most effective approach is pre-training foundation models on internet-scale video datasets, not just simulation or tele-operated data. This vast, diverse data provides a deep, implicit understanding of physics and object interaction that is impossible to replicate in controlled environments, enabling true generalization.

For physical AI systems like robots, data quality hinges on diversity, not just quantity. A robot trained to make a bed in one specific lighting condition may fail completely if the lighting changes or the bed is moved. This brittleness highlights a key challenge: training data must capture a wide variety of contexts and edge cases to enable real-world generalization.

Unlike cars, which gather data passively, humanoid robots need active training. To solve this, Musk's strategy is to build a physical 'academy' of 10,000-30,000 Optimus robots performing self-play on various tasks, using this real-world data to close the 'sim-to-real' gap from millions of simulated robots.

Progress in robotics for household tasks is limited by a scarcity of real-world training data, not mechanical engineering. Companies are now deploying capital-intensive "in-field" teams to collect multi-modal data from inside homes, capturing the complexity of mundane human activities to train more capable robots.

The choice between simulation and real-world data depends on a task's core difficulty. For locomotion, complex reactive behavior is harder to capture than simple ground physics, favoring simulation. For manipulation, complex object physics are harder to simulate than simple grasping behaviors, favoring real-world data.

The adoption of powerful AI architectures like transformers in robotics was bottlenecked by data quality, not algorithmic invention. Only after data collection methods improved to capture more dexterous, high-fidelity human actions did these advanced models become effective, reversing the typical 'algorithm-first' narrative of AI progress.

Ken Goldberg quantifies the challenge: the text data used to train LLMs would take a human 100,000 years to read. Equivalent data for robot manipulation (vision-to-control signals) doesn't exist online and must be generated from scratch, explaining the slower progress in physical AI.

Despite industry hype, humanoid robots are not imminent. They lack the massive datasets of real-world, unpredictable interactions needed to operate safely and usefully in a home environment, which is far more complex than a structured factory floor.