Gravitational force on Earth's surface varies based on nearby mass. For example, near mountains, gravity is stronger than in cities.
These small differences are usually too tiny to notice without sensitive instruments.
A gravity gradiometer measures how much faster a ball falls in different places, revealing differences in ground density.
For example, it can detect oil deposits because they are less dense than rocks, causing a ball to fall slower above them.
NASA scientists propose using a quantum gravity gradiometer (QGG) on a satellite to measure small changes in Earth's mass distribution from space.
In a QGG, atoms are cooled to near absolute zero and manipulated by lasers, causing them to shift in response to gravity.
This shift is very sensitive and can detect tiny changes in acceleration (as small as 10-15 m/s² over 1 meter).
The QGG could measure large structures like mountains, for example, the weight of the Himalayas.
The proposed QGG would weigh 125 kg, and use about 350 watts of power.
NASA plans a demonstration mission to test the QGG in space, advancing both gravity measurement and quantum technology.
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