01 · Shapes
Circle
v = √(μ/r). Higher is slower. 400 km is 6% of a radius — skimming the well, missing Earth on purpose, sixteen dawns a day.
In English
In a circle, faster is lower. 400 km up is still hugging Earth — six percent of a radius. You stay up because you are moving sideways at 7.8 km/s, not because gravity turned off.
- Try this
- Drag 200 km to 2 000 km. Speed should fall. Period should stretch. Count sunrises.
- Keep this
- Higher = slower = longer day. LEO is skimming, not visiting another country.
Lab · how close LEO really is
Circular speed is √(μ/r). Higher is slower, not faster — you have climbed out of a gravity well. The ring hugs Earth. 400 km is 6% of a radius. Airplanes are the thickness of paint.
Altitude 400 km
- Speed
- 7.67 km/s
- Period
- 92.4 min
- Sunrises / day
- 15.6
v = √(μ/r), T = 2π √(a³/μ) with a = r. μ = 3.986×10¹⁴ m³/s², R = 6371 km. ISS ~400 km, ~7.67 km/s, ~92 min.
Micro-g is free-fall, not missing gravity. Weightlessness is missing a floor. The well is still there; you are moving sideways fast enough to miss it.