# New Gravity Map released.November 21, 2001 2:16 PM   Subscribe

New Gravity Map released. The Grace satellites have sent back the first monthly installment of five years' worth of gravity mapping data. [145K jpg] The upshot? Move to India - you'll weigh 1% less.
posted by gleuschk (15 comments total)

Initial link courtesy of boingboing.
posted by gleuschk at 2:18 PM on November 21, 2001

Yuk. It looks like a tumor.
posted by Su at 2:31 PM on November 21, 2001

Getting the Lowdown on Gravity: An earlier interview of Dr. Michael Watkins, project scientist for the Grace mission, from JPL/NASA.
posted by Carol Anne at 2:48 PM on November 21, 2001

Cool stuff.
Thanks for the interview link Carol Anne.
One thing I don't understand,

"In the new map, the lower the elevation the weaker is the pull of gravity. " (from front page link)

I learned that as you get further away from the earth, the force of gravity decreases. So you would weigh less at a higher altitude, right?

I don't get it.
posted by computerface at 3:02 PM on November 21, 2001

I think it's just a useful heuristic, not any kind of direct correlation. It's basically the same as colors on a map, not saying that the represented height is how things should look.

For that, you want geoids, which are the shape that mean sea level would take if it could (technically, "a surface on which the gravitational potential energy has the same value everywhere").
posted by gleuschk at 3:15 PM on November 21, 2001

Computerface: they're just saying that on the map, the way Earth is drawn, areas where the surface is closer to the center of the Eather, that's where gravity's effect is the least.

Btw, that map is freakin cool.
posted by ookamaka at 3:17 PM on November 21, 2001

Actually, ookamaka, gleuschk, and computerface... I think that we're meant to take the statement at face value.

Remember, there are a number of things which dictate gravity: mass, and one's proximity to mass.

At higher altitudes (as long as you're still on terra firma), you will tend to be very close to much more mass (mountains tend to have a lot of mass even below them) than when you're at sea level (where the earth's crust tends to be thinner -- tends to be) -- diagram, and explanation... both of which were found searching Google.

At least that's my understanding.
posted by silusGROK at 3:42 PM on November 21, 2001

My geophysics is a bit rusty but here goes:

Gravity also varies due to the density of material. The granitic material which makes up the continents is less dense than the oceanic material (it is essentially floating on top of it). A pile of granitic material will cause a gravitaional low because it is both light and it displaces the denser material below it. Gravity lows can also occur due to regions of high temperature in the mantle, where the material is less dense.

If anyone knows better, feel free to correct me.

Cheers!
posted by phatboy at 3:46 PM on November 21, 2001

Vis10n: That's my understanding, too, as far as it goes, but I think there are other variables too (the article mentions something about the tectonic plates off the coast of India - I take this to mean there's a big hunk of mass down there). I'm pretty sure this isn't just an exaggerated relief map.

Or, what phatboy said.
posted by gleuschk at 3:52 PM on November 21, 2001

Woohoo another reason we Indians have it best.

I wonder if it's connected with the fact that the Indian sub-continent is actually from Antartica not from Asia?
posted by riffola at 3:56 PM on November 21, 2001

Oops should've finished reading the main article.
posted by riffola at 4:00 PM on November 21, 2001

saw the APOD pic on blogdex, the explanation says they don't know what causes it, but it may be due to "deep underground structures" from the formation of the earth. sort of related, experiments are underway to better understand the earth's inner core. btw, doesn't it look like a butt?
posted by kliuless at 4:15 PM on November 21, 2001

Dang. Change "hunk" to "absence" so it, you know, makes sense and stuff.
posted by gleuschk at 5:32 PM on November 21, 2001

So if I ship 500 pounds of coffee to India, they'll only pay me for 495 pounds because of the difference in gravity?

No wonder India does so poorly at the Olympics each year, they're training at a lower gravity.
posted by bobo123 at 5:55 PM on November 21, 2001

Hmm... I thought I was heavy.... now I'm 1% heavier!! :(
posted by arnab at 7:42 PM on November 22, 2001

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