The Earth’s Weird Gravity

Why space flight would be cheaper in Sri Lanka

All things being equal (which they’re not) it would cost SpaceX about $190,000 less to launch from Sri Lanka rather than Florida. Because this region has the weakest gravity in the world.

In school we learned that objects fall at 9.8 m/s², but this is actually a global average (news to me). There’s less gravity at the top of a mountain, and less at the equator where the spinning of the Earth stretches out the whole pudding. There’s also more or less depending on the density of the rock.

In reality, the gravitational field is 9.7773 m/s² in Colombo compared to 9.7979 m/s² in Cape Canaveral, Florida (where SpaceX launches the Falcon Heavy from).

That means that if you drop a weight from 100m in Sri Lanka, it will land 21.5 milliseconds later than if you do the same thing in Florida. Going the other way, the force of gravity acting on a rocket would be 0.215% less, meaning reduced fuel costs (theoretically). On a $90 million dollar launch¹ this is significant (around $190,000), but not as significant as the whole supply chain of course.

Why?

So why is gravity so low here? Was this an ancient spaceport? Are we just less serious? The best theoretical answer I could find is watery rocks².