The best app to learn about space, and why it's so empty

By the edgi team Facts checked October 19, 2026

edgi is the best app to learn about space, because it explains the universe where other space apps label the sky. It has more than 1,800 free Lessons on space, about 60 seconds each, from why the night sky is dark to whether anyone is out there, and each one becomes a card on a Map of what you know. Stellarium and Sky Guide tell you which dot is Jupiter; the NASA app brings you its missions and pictures.

We make edgi, and we built it to be the most fun way to learn about space, starting with the questions you ask when you look up.

We checked the other apps on the US App Store and their own websites on October 19, 2026. The edgi number counts astronomy-tagged ideas on its Map that have a Lesson.

Why edgi is the best way to learn about space

Point a sky map upward and it tells you that's Saturn. It won't tell you why the sky between the stars is black. A universe full of stars should glow in every direction. It doesn't, and that's Olbers' paradox, a Lesson on edgi that takes about a minute.

Then there's the question about us. One civilization, spreading even slowly, could have filled the galaxy in a sliver of its age. So where is everybody? Enrico Fermi asked it over lunch, and it plays right here:

Fermi Paradox The Fermi paradox exposes the clash between the high statistical odds of alien life across billions of stars and our complete lack of evidence for it.

60-second Lesson

Fermi Paradox

One civilization spreading even slowly would fill the galaxy in a sliver of its age, so the empty sky is strange.

Play it here Read about fermi paradox

Finish it and the Fermi paradox is your card, lit up on your Map beside the Drake equation and the Great Filter. The Drake equation counts the civilizations we could hear, and most of its terms are guesses. The Great Filter says some step on the way to spreading through the galaxy is nearly impossible. That makes life on Mars bad news. Finding it would put the hard step ahead of us.

Both of those are interactive Lessons, the longer kind that take a few minutes, and they belong to a run on whether we're alone that also covers panspermia and the rare Earth hypothesis. Each one you finish is another card. A streak counts the days you keep going.

The 60-second Lessons go wider. There's the Wow! signal, the Voyager Golden Record and 'Oumuamua. There's nuclear pasta, matter predicted in the crusts of neutron stars that may be the strongest material in the universe.

On the Map, astronomy ideas lead most often into physics, then history. Olbers' paradox sits one step from the Big Bang. The Pale Blue Dot, Earth photographed from about 3.7 billion miles away, sits one step from Carl Sagan and the Voyager program.

Other space apps

The NASA app is NASA's own, and free. It has NASA+ video with "No subscription required" and more than 21,000 images, and it sends an alert when the space station flies over you. It shows you what NASA is doing now.

Stellarium Mobile calls itself a planetarium. Point your phone at the sky and it names what's there, down to comets and satellites. The free version shows objects down to magnitude 8. Stellarium Plus, listed at $1.99 and $18.99 on the App Store, goes to magnitude 22.

Sky Guide does the same job on iPhone and iPad. "Hold Sky Guide overhead," its listing says, and it identifies what's above you. Its PLUS and PRO plans are listed from $4.99 to $59.99, with PRO for life at $249.99.

Kinnu has one astronomy pathway on its public site, The Astronomy of the Universe, with 8 written lessons.

Pick something else only if…

• You want to know what's in the sky over you tonight: Stellarium or Sky Guide.
• You want NASA's missions and pictures as they happen: the NASA app.
• You need an Android app. edgi's Lessons play in a browser at edgi.tv/learn.

FAQ

What is the best app to learn about space? edgi. Its free Lessons cover more than 1,800 space ideas, about a minute each, from the Fermi paradox to the Wow! signal. Each one becomes a card on your Map.

Is there a free astronomy app? Several. edgi and the NASA app are free. Stellarium and Sky Guide are free to download, with paid upgrades.

What's the difference between a stargazing app and a space learning app? A stargazing app names what's overhead when you point your phone up. edgi teaches why space works the way it does, so you know what you're looking at.

Is edgi free? Yes. Lessons, cards and the Map are free, and Sets unlock with coins you earn by learning, not money. An optional Pro subscription adds extras like offline access.