Synthesized answer
The provided passages do not explicitly list the unanswered questions from "The Problem of Increasing Human Energy" by Nikola Tesla.
The passages describe the general themes and focus of the book, stating that it covers "emerging scientific challenges, new types of energy, and how best to harness the sun's energy" [1]. However, they do not specify which particular questions remain unanswered within these topics.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: The Problem of Increasing Human Energy by Nikola Tesla Description: In this text, Tesla focuses on the survival of the human race from his unique scientific vantage-point. Topics include emerging scientific challenges, new types of energy, and how best to harness the sun's energy.