Suppose you are a passenger in a spaceship, you look outside, and you notice that, from your vantage point, the Sun and the Earth appear to be almost exactly the same size. Question: Is it possible that you are currently in orbit around the Earth? Suppose instead that it's the Earth and Moon that appear the … Continue reading Hill Spheres and apparent radii
As seen in the Earth's sky, the Moon and Sun are very close to the same size. I've seen it asserted a handful of times that this situation is unique in the Solar System (example). But is that actually true? It always sounded a little suspicious to me, so I decided to take a closer look. … Continue reading Solar eclipses on other planets
Maybe you remember that viral internet graphic from a few years ago showing how the other 7 major planets in the Solar System could fit neatly between the Earth and the Moon. I'm not sure if I'm supposed to be surprised by that, but it's a mildly interesting coincidence that the distances are so close. … Continue reading Could all the planets fit between the Earth and Moon?
I didn't want my first real post here to be about file formats, so I'll go with the next best thing: space aliens. I don't know whether extraterrestrial intelligent life (ETI) exists in the observable universe. A lot of very smart people think it does. But based on humanity's current observational and theoretical knowledge, it … Continue reading We’re probably alone