Satellites map the gravity around the Earth

--------- #1401 - Gravity Map Sees Loss of Groundwater?

- Attachments : GRACE satellites, gravity map

- In March 2002 science launched 2 satellites. 310 miles up, one following the other by 140 miles. There was a precision microwave transmitter and receiver installed that linked the two together to precisely measure the distance between them. The accuracy of the range measurement was to within 10 micrometers, 0.001 centimeters.

- 9 years of data collection measuring minor variations in Earth’s gravity as the satellites circle the Earth has lead to thousands of discoveries. From lakes under the Antarctic to a dropping water table around the globe, to measuring the pressure at the bottom of the oceans. Called the “ Gravity Recovery and Climate Experiment”, GRACE it provides an accurate gravity of the globe. The satellites circle the Earth 15 times a day.

- Gravity is determined by mass when distance is held constant.

------------------------- F = G * M * m / r^2

---------Force of Gravity = Gravitational Constant * Masses / distance between centers.

- As the satellites pass over different areas of the globe they respond to the pull of gravity directly below. As the 1^st satellite passes over a mountain range, more mass means more gravity, the satellite gets pulled forward increasing the distance between it and the tandem 2^nd satellite 140 miles following behind. The 2^nd satellite will decelerate later passing over the same area.

- By measuring the constantly changing distances between the 2 satellites combined with GPS data on their positioning science can construct a detailed map of Earth’s gravity. One of the thousands of new discoveries made from this experiment is that “ farmers are pumping too much water out of the ground.” Water moves around over time creating small gravity fluctuations that the satellite orbital motions respond to. Science can detect a centimeter rise or fall of groundwater over an area the size of Indiana.

- In China water levels have been dropping 6 to 7 centimeters each year beneath the plains in the northeast.

- California’s Central Valley is loosing 4 cubic kilometers of water every year. The ground has been sinking for decades as 1/6th of the nation’s irrigated land is producing food using ground water. California is using groundwater faster than rainfall can keep up. GRACE satellites can only measure changes in groundwater. They can not tell how much water is left.

- Like our National Debt, our water use has become “ unsustainable”. Policy makers and leaders need to take charge today and not let these problems be passed on to our kids and grandkids. We need to educate and provide incentives for farmers to use better irrigation systems. We need innovative ways to channel water during wet seasons into aquifers rather the letting it run off in to the ocean. Remember there are always 2 decisions to be made, what to do, and how to do it. The how should be education and bottoms up and not tops down mandates from Sacramento.

- Gravity mapping discovered over 280 liquid water lakes under the Antarctic. Recently a Russian team drilled a 12,366 foot well into the ice and penetrated the lake that was 2 miles below. This freshwater lake is the size of Lake Ontario only it is fossilized water 15,000,000 to 34,000,000 years old.

- The Russians have been drilling this hole for over 10 years. The hole is 5 inches in diameter and filled with kerosene to keep it from freezing. When the drill punched through into the lake pristine water rushed upward and froze a plug that prevented contamination of the fossil water.

- Lake Vostok has been sealed off. Science will next recover samples of the water to see if life forms exist there. If they find life it is a great boon to astronomy. Many belief that life could exist below the frozen surface of the moon, Europa, that is orbiting the planet Jupiter. ( See Reviews #1361, and #1152, and # 812 to learn more about Europa.) An announcement will be made shortly, stay tuned.

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(1) Other reviews on gravity
#974 Gravity- What is it really?
#816 Why is gravity so small?
#1399 Earth’s gravity warps space-time?
#917 Gravity waves.
#1155 What are gravity waves?
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707-536-3272, Thursday, February 9, 2012