Did you know that gravity isn’t the same everywhere on Earth? In Canada’s Hudson Bay, gravity is slightly weaker than the global average—an anomaly scientists have been studying since the 1960s. As such, traveling to that particular area would cause you to lose weight instantly, though not in the way you probably want.
This variation happens because Earth’s mass isn’t always perfectly distributed, so some areas have a stronger gravitational pull than others. In Hudson Bay, gravity is about 0.004 percent less than Earth’s average, a difference subtle enough to require highly accurate scales to detect.
Scientists have proposed two main theories to explain this gravitational anomaly. The first is tied to the Ice Age. About 20,000 years ago, the Laurentide Ice Sheet, a massive glacier over 3 kilometers thick, covered much of North America. Its weight compressed the land beneath it, pushing down Earth’s crust.
Although the ice melted quickly at the end of the Ice Age, the crust has been much slower to recover. Today, it’s still rebounding at a rate of about 12 millimeters per year, though it may take up to 300,000 more years to fully return to its original position.
This difference could be the cause of the gravity anomaly. This “dent,” as some have referred to it, means there is less mass in the Hudson Bay region, which could result in slightly weaker gravity in the area. And since gravity is constantly reshaping Earth’s surface, this theory makes a lot of sense.
The second theory involves movements deep within the Earth. Beneath the crust lies the Earth’s mantle. This layer of molten rock circulates over long periods, moving in currents heated by the Earth’s core. These currents push and pull on the crust, affecting the land above.
In Hudson Bay, this downward pull reduces the area’s mass, creating a weaker gravitational pull, thus causing the gravity anomaly scientists first noticed in the 1960s.
In 2002, satellite data confirmed that both theories were correct. Hudson Bay’s lower gravity is due to a combination of the crust’s slow rebound from the Ice Age and the mantle currents beneath the surface.
Even after the crust has completely rebounded, the gravitational difference in this region will likely remain. It isn’t exactly the most exciting weight loss solution—or one that will stick matter if you leave the region. However, it’s still a really cool scientific fact that you can use to wow your friends next time you go out to dinner.
