Missing gravity near Canada's Hudson Bay
Hudson Bay from space. (NASA/GSFC)
Scientists are talking about a strange case of “missing gravity” near the Hudson Bay area of Canada.
It’s just a tiny deviation from the norm, nothing that anyone could feel. But it’s large enough to be detected by NASA’s GRACE satellites in space. Gravity relates to how much matter something contains. And Earth’s crust is known to be thinner in Canada’s Hudson Bay area.
Scientists believe the reason was a huge ice sheet that covered Canada and the northeastern U.S. 20,000 years ago. The weight of the ice pressed on that region, much like a finger pushing on a spongy cake. When the ice melted, it left a huge depression in the Earth.
Jerry Mitrovica: It was sufficient to raise sea levels globally by about 60 meters, so that’s about 200 feet.
That’s Jerry Mitrovica, a professor of physics at the University of Toronto. He led a study that mapped Canada’s gravity field in detail, to understand what that ice sheet looked like 20,000 years ago.
Jerry Mitrovica: What we noticed was that the gravity field uplift indicated that there wasn’t a single dome that covered Canada and the northeastern U.S. There were two domes, two large domes.
Knowing what the ice sheet looked like back then lets scientists pin down variations in modern–day models of Earth’s climate.
Our thanks today to NASA, explore, discover, understand.
Mitrovica added that plate tectonics also played a role in forming the two large ice domes. In addition to Earth’s plates moving from side–to–side, they also move up and down.
Our thanks to:
Jerry Mitrovica
University of Toronto
Prof. of Physics
What exactly is gravity? I know it’s caused (created?) by ‘the amount of matter something contains’ and what it does—a force of attraction. But what exactly is it?
I think the short answer is that scientists aren’t entirely sure what gravity is.
The idea of two massive objects performing action at a distance bugged Einstein to the point where he came up with something new, back in his day anyway. And that is the notion of gravity as the curvature of space time, where big objects, such as our Earth, warp space and time enough to tug on our moon and keep it from flying away forever.
I invite those interested in more about gravity to check out Dennis Overbye’s article in the New York Times, What is Gravity, Really?
I have presented evidence in my book GRAVITATIONAL FORCE OF THE SUN and in a recent article “New Concepts in Gravitation” published in PHYSICS ESSAYS Volume 18, Number 1. pages 37-49 that gravitational force is independent of the mass.
I really don’t know what the sentence below means.
“Gravity relates to how much matter something contains.”
Dose it mean what contains in the crust or the area?
depending on what the substance is there, would the gravity be various?
If there is someone else here, please explain that for me.
Ms. Spolter is correct in referring to her paper’s publication. She does, indeed, PRESENT a mass/gravity disconnect in that paper. It is not yet clear that she has DEMONSTRATED it, though. The debate continues. We’ll see . . .
Please see “Problems with the Gravitational Constant” in the INFINITE ENERGY Magazine, http://www.infinite-energy.com, Issue 59, 2005, page 39.
Do you think that zero gravity is possible?