By imagining Earth at the center of a celestial sphere, he used a coordinate system similar to latitude and longitude, which had recently been devised, to measure the precise positions of the stars.

Today, I want to talk about the equatorial coordinate system ... If we project Earth’s equator and poles onto the celestial sphere, we get the celestial equator and the north and the south ...

Flat Earth conspiracies seem to pop up everywhere, but how do we actually measure the shape of our planet? Enter geodesy, the ...

But we’re stuck with it because we perceive the sky as a sphere. Other coordinate system units could work, but in my opinion, they’re even harder to use, so we’d just wind up going back to ...