In the 1960’s, scientists started charting the Earth’s gravitational field. They were looking for inconsistencies.
They found what they were looking for. It was discovered that Earth’s gravitational field varied quite a lot.
In Canada, they found areas that were “missing” gravity. The Hudson bay is highlighted as a zone in Canada where gravity is much weaker than other parts of Earth.
(Maybe this drop in gravity caused the mutiny of against explorer Henry Hudson. Hudson, his son, & loyal crew members were set adrift in Hudson bay by mutineers in 1611)
Two theories have been brought to light.:
1. Convection: Convection pulls the Earth’s continental plates downwards, which decreases the mass in that area & decreases gravity. Convection is thought to be occurring in the Hudson Bay area.
2. Ice Sheet: The Laurentide Ice Sheet melted 10,000 years ago. It left an enormous indent in the Earth which is suspected to mess with gravity. That large indent is in the Hudson Bay zone.
Regardless of how this happens, it’s very interesting that it’s happening. It’s also now clear that the Canadians have been using this to their advantage in snowsports for years.
We’d love to see an NBA basketball game played there to see if the difference is really noticeable.
Learn a lot more about Earth’s Missing Gravity: howstuffworks.com