The Planetarium Test
One prompt asked two models to build a working planetarium from first principles — real orbital math, no libraries, no data files. Both shipped a working night sky.
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The exact prompt we used
prompt.txt — fed identically to both models
Build a complete planetarium as a single HTML file. Compute the live positions of the Sun, Moon, and five visible planets from Keplerian orbital elements and spherical astronomy — do not look positions up, do not use libraries, do not fetch data. Let me pick any location and any date from 1900 to 2100, show the sky chart with horizon and azimuth, and animate time forward and backward.
Don’t take our word for it. Paste this into any AI model and compare your result against the outputs below.
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What to look for
Try this
Set both to your city and tonight's date — then check the Moon phase against the real sky outside.
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