Did you know that gravity is not the same everywhere on Earth? In Canada’s Hudson Bay, gravity is slightly weaker than the global average – an anomaly that scientists have been studying since the 1960s. As such, traveling to this particular area would make you lose weight instantly, but not in the way you would probably like.

This variation occurs because Earth’s mass is not always perfectly distributed, so some areas have a stronger gravitational pull than others. In Hudson Baygravity is about 0.004 percent lower than Earth’s average, a difference subtle enough to require very precise scales to detect.

Scientists have proposed two main theories to explain this gravitational anomaly. The first is linked to the ice age. About 20,000 years ago, the Laurentide Ice Sheet, a huge glacier more than 3 kilometers thick, covered a large part of North America. Its weight compressed the earth below, pushing the Earth’s crust downward.

Image source: Reid Wiseman/NASA

Although the ice melted quickly at the end of the Ice Age, the crust was much slower to recover. Today, it is still bouncing back at a rate of about 12 millimeters per year, although it may take up to 300,000 more years to fully return to its original position.

This difference could be the origin of the gravitational anomaly. This “hump,” as some call it, means there is less mass in the Hudson Bay region, which could result in slightly lower gravity in the region. And since gravity constantly reshapes the Earth’s surfacethis theory makes a lot of sense.

The second theory involves movements deep inside the Earth. Beneath the crust is the Earth’s mantle. This layer of molten rock circulates over long periods of time, 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 mass of the area, creating a weaker gravitational pull, thus causing the gravitational anomaly first noticed by scientists 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 slow rebound of the crust following the ice age and subsurface mantle currents.

Even after the crust has completely rebounded, the gravitational difference in this region will likely persist. It’s not exactly the most exciting weight loss solution– or one that will remain important if you leave the region. However, it’s still a really interesting scientific fact that you can use to impress your friends the next time you go out to dinner.