Labs / Astronomy
Sidereal vs Solar Day
Earth turns on its axis and, at the same time, edges a little further around the Sun. Drag across the view to spin the planet, or let it run, and follow the surface marker as it points first back at a distant star and then, a moment later, back at the Sun. That small gap is why a solar day is a few minutes longer than a sidereal one.
spin 0°to Sun 0°sidereal 21h 20m 00ssolar 24h 00m 00s
What to try
- After the marker points back at the star, how much more must Earth turn before it faces the Sun again?
- Switch to a short 8-day year. Does the extra rotation get bigger or smaller, and why?
- Turn on both reference lines. What is the growing amber wedge between them actually measuring?
- Set it to the real Earth (365 days). Why does the sidereal day come out near 23h 56m instead of a round 24 hours?
- If Earth orbited the other way, or didn't orbit at all, would the sidereal and solar day still differ?