Start here · Essential guide
Making Sense of the Universe: A Guide
A plain-language tour of the universe's scale and structure, from planets and stars to galaxies and the observable universe, and what we still do not know.
Universe and Matter
Our Universe
Space, the solar system and how we picture the cosmos.
Challenging the Notion of a Flat Earth
Why scientists conclude Earth is a sphere: ships, shadows, star positions, time zones and spaceflight, explained respectfully and without an invented debate.
Common Misconceptions About the Solar System
Seasons, the Moon's far side, the color of the Sun, astronaut weightlessness and more: gentle corrections to common mistaken beliefs about our solar system.
Deconstructing the Concept of Time
How humans measure time, from sundials to atomic clocks, how relativity changes the picture, and the questions about time that physics has not yet settled.
Fun Facts About the Universe
Well-established, rounded facts about the universe's age, size and contents, from 13.8 billion years of history to the stuff stars and people are made of.
How Big Is the Observable Universe?
What observable means, why the observable universe is about 93 billion light years across, and why the whole universe may be larger or even infinite.
Mind-Blowing Facts About Space
Striking but verified facts about space: vacuum, gravity in orbit, extreme temperatures, huge distances and dense stars, with the hype carefully removed.
Related topics
More in universe and matter
Physics and Matter Modern physics, light, the elements and everyday math. Stars and Galaxies How stars live and die and how galaxies and the early universe are understood. Planets and Space Exploration Missions, the Moon, eclipses and the search for life beyond Earth. Forces, Energy and Motion Classical physics that explains everyday motion, heat, sound and electricity. Chemistry and Materials Reactions, everyday substances and how common materials are made.