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View Full Version : Gravity’s Magic: New Seafloor Map Shows Earth’s Uncharted Depths



Fraser
2014-Oct-15, 01:50 PM
Volcanoes! Seafloor spreading! Hidden ridges and mountains! These are the wonders being revealed in new maps of Earth’s sea floor. And no, it didn’t require a deep-sea dive to get there. Instead we got this information from a clever use of gravity (combining the data of two satellites making measurements from orbit.) The data has […]

More... (http://www.universetoday.com/115302/gravitys-magic-new-seafloor-map-shows-earths-uncharted-depths/)

grapes
2014-Oct-15, 03:41 PM
Volcanoes! Seafloor spreading! Hidden ridges and mountains! These are the wonders being revealed in new maps of Earth’s sea floor. And no, it didn’t require a deep-sea dive to get there. Instead we got this information from a Tclever use of gravity (combining the data of two satellites making measurements from orbit.) The data has […]

More... (http://www.universetoday.com/115302/gravitys-magic-new-seafloor-map-shows-earths-uncharted-depths/)

Article ends with this paragraph:


Long-time readers of Universe Today may also recall a gravity map from ESA’s Gravity Field and Steady-State Ocean Circulation Explorer (GOCE), which revealed Earth’s gravity as a lumpy potato shape in 2011.

A little misleading! The earth is smoother and rounder than your average billiard ball. Only by removing the centrifugal bulge (~20km) and exaggerating the imperfections (~100m), does it look like a potato.

Amber Robot
2014-Oct-15, 05:03 PM
Article ends with this paragraph:

A little misleading! The earth is smoother and rounder than your average billiard ball. Only by removing the centrifugal bulge (~20km) and exaggerating the imperfections (~100m), does it look like a potato.

It is smoother, but is it rounder?

grapes
2014-Oct-15, 05:29 PM
Not your premium billiard balls, but your OK billiard balls... :)

Years ago I got the specs from Brunswick and that's the conclusion I drew from that. I probably wouldn't mind playing with the earth as a cue ball...

Amber Robot
2014-Oct-15, 05:40 PM
Not your premium billiard balls, but your OK billiard balls... :)

Years ago I got the specs from Brunswick and that's the conclusion I drew from that. I probably wouldn't mind playing with the earth as a cue ball...

You're correct. I just looked up the specs on the World Pool-Billiard Association website and the allowed error in the roundness of a billiard ball is almost an order of magnitude larger than the difference of the polar and equatorial diameters of earth.

grapes
2014-Oct-15, 06:55 PM
Interesting. An order of magnitude, heh? I looked up that website, is this it:
http://www.wpa-pool.com/web/WPA_Tournament_Table_Equipment_Specifications


All balls must be composed of cast phenolic resin plastic and measure 2 Ľ (+.005) inches [5.715 cm (+ .127 mm)] in diameter and weigh 5 ˝ to 6 oz [156 to 170 gms].

Amber Robot
2014-Oct-15, 07:06 PM
That's what I found. 0.127/5.715 is 0.022 , and what I found from Wikipedia article on the Earth was that the diameter difference is around 0.0033.

Edited to add:

Wait a second!! I made a mistake. I didn't see that they changed units in the metric. If you take 0.005/2.25 you get 0.0022, which is rounder than the Earth. If I had done the inches first I would have seen this. So, for the metric I should have converted the error in mm to cm first and done 0.0127/5.715 = 0.0022.

So, the Earth is both smoother and rounder than a billiard ball. Which is what I thought I had convinced myself of when I looked this up a while back.

BigDon
2014-Oct-16, 02:34 PM
Where are the big maps of this?