Explore our Universe is an online educational resource that strives to make the sometimes bizarre and abstract ideas in theoretical physics accessible to as many people as possible. Our collective understanding of the universe is one of human kind’s greatest achievements — one that should be shared and celebrated by all, not just the experts.

You will find explanations of some of the amazing things we do know about our universe, and equally important, descriptions of what we don’t know — the deep questions that are engaging some of the brightest minds in theoretical physics today. This material is intended to be of interest to students, teachers and indeed anyone wanting a more in depth appreciation for and understanding of the nature of our universe at its most foundational level.

• The Essence of General Relativity, Part I: Einstein’s Rotating Disk Thought Experiment