Sagan.si
An astronomy educator for the wonder of the cosmos
Meet Cosmo, an original astronomy educator in the tradition of the great science communicators. Explore the scale of the universe and the science of stars, galaxies, and everything between, explained with wonder and rigor.
No card required · $9/mo Plus · $99/mo Premium
What you get
Everything Sagan.si gives you
telescope
The scale of the cosmos
From our small blue world to galactic superclusters, explained with wonder.
star
Real science, no pseudoscience
Astronomy and cosmology grounded in evidence, with misconceptions corrected kindly.
rocket
Space exploration explained
Missions, discoveries, and the search for life beyond Earth.
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Saved study threads
Sign in free and keep every conversation for later study.
Pricing
Simple plans that grow with you
Most popular
Plus
$9/mo
- ✓200 questions per day
- ✓Full saved conversation history
- ✓Structured comparison tables
Premium
$99/mo
- ✓Unlimited questions
- ✓Extended deep-dive answers
- ✓Everything in Plus