The greatest technical ones are: - Countering aging / human rejuvenation. - Atmospheric carbon capture and utilization. - Strong materials / bringing materia

The greatest technical ones are: - Countering aging / human rejuvenation. - Atmospheric carbon capture and utilization. - Strong materials / bringing materials up to their theoretical strengths. (The theoretical strength of fiberglass is ~40GPa; the best samples generally measure at ~5GPa.) Yet it's the non-technical challenges surrounding governance, how to handle social media, how to deal with falling birthrates, etc., that are much more pressing.