Why are rockets launched eastward?
The Earth's surface is already moving east at up to about 1,670 km/h at the equator, and launching in that direction means the rocket starts with that speed for free.
Simple intuition
The plain reason, in everyday words
Getting to orbit is not really about going up. It is about going sideways fast enough that when you fall, you keep missing the ground. A rocket needs to reach something like 28,000 km/h sideways, and almost all of its fuel goes into building up that sideways speed. Now, the Earth is spinning, and everything on its surface is being carried east with it. Stand at the equator and you are already travelling east at roughly 1,670 km/h without doing anything. If a rocket launches towards the east, it starts with that speed already in its pocket. If it launched west, it would have to cancel out that 1,670 km/h first and then build up the full amount in the other direction. That is a difference of over 3,000 km/h in a job where every extra bit of speed costs a great deal of fuel.
Rockets go east because it is 'downhill' or because the atmosphere helps.
There is no downhill and the atmosphere only hinders. The entire benefit is the velocity the rotating planet has already given the vehicle relative to space.
Getting to orbit is mostly about altitude.
Altitude is the cheap part. A suborbital hop above 100 km costs well under a fifth of the delta-v needed to actually stay in orbit; the expensive part is horizontal speed.
The rotational boost is a small detail.
465 m/s is roughly five per cent of the total delta-v budget, and because payload responds exponentially to mass ratio, five per cent of delta-v is a large fraction of deliverable payload.
It reframes what a rocket is doing. Once you see orbit as a horizontal-speed problem rather than a height problem, a lot of things fall into place: why reentry is violently hot, why changing an orbit's plane is so expensive, why a satellite in low orbit circles the planet every ninety minutes, and why the map of the world's launch sites looks the way it does.
Who worked it out
Konstantin Tsiolkovsky derived the rocket equation in 1903, establishing the logarithmic relationship between mass ratio and achievable delta-v that makes every saved metre per second matter so much.
What problem forced it
The practical question became urgent in the 1950s, when both superpowers had to choose permanent launch sites and discovered that latitude and downrange geography were strategic assets.
How it changed since
Site selection has stayed remarkably stable, but the calculus around it has shifted. Reusable first stages introduced a competing constraint — the booster has to come back — and sea-based launch platforms were tried specifically to reach the equator, with Sea Launch operating from the Pacific between 1999 and 2014.
Why reentry generates so much heat
The same horizontal speed has to be given back, and that energy has to go somewhere.
Why geostationary orbit is at one specific altitude
Follows directly from the relationship between orbital speed and radius.
Written for Curio rather than collected from a forum — it is part of the curated corpus that ships with the platform. The references it draws on are listed under Sources.
Why are airplane windows round?
Sharp corners concentrate stress into a single point, and at cruising altitude a pressurised cabin pushes hard enough on that point to tear the fuselage open.
A natural next question