Astronomy is one of the few sciences that I've studied that has given me existential dread. In particular, the scale of the universe just hurts my brain: If yo

Astronomy is one of the few sciences that I've studied that has given me existential dread. In particular, the scale of the universe just hurts my brain: If you were to scale down the Sun to the size of a coarse grain of sand (1 mm), then the orbit of the Earth would be about 20 cm across, with the planet itself being microscopic at this scale (10 micrometers). Jupiter would be a barely visible speck 55cm from the Sun. At this incredibly tiny scale, the next nearest star in the galaxy is about 30 kilometers (18 miles) away! That's roughly the same as a trip across a typical city, but our Voyager probes at this scale have gone only 15 meters over a period of 45 years! That's comparable to the rate at which hair grows (1 mm/day). Hence, a good mental model for thinking about the scale of our galaxy is: Stars are grains of sand separated by tens of kilometers on average across a circular space the size of the orbit of the Moon.