Context: NASA scientists have proposed that an advanced quantum gravity gradiometer (QGG) could be placed onboard a satellite and launched into low-earth orbit. The instrument could study small changes in the earth’s distribution of water, ice, and rocks to inform studies of climate change.
Relevance of the Topic: Prelims: key facts about Quantum Gravity Gradiometer and its Application.
Variation of Gravitational Force:
- Gravitational force on the Earth’s surface is non-uniform. The amount of gravitational force one experiences on the earth’s surface depends on the amount of mass nearby.
- The force is directly proportional to the mass. Force equals to Mass multiplied by its Acceleration (F = m · a).
- This difference in force between two places is too small and requires the most sensitive instruments for its detection. One such instrument is the gravity gradiometer.
Quantum Gravity Gradiometer
- Quantum Gravity Gradiometer is a highly-sensitive instrument that can detect minute variations in Earth's gravitational field by harnessing the principles of quantum mechanics.
Working of QGG
- QGG uses ulta-cooled rubidium atoms (cooled to near absolute zero) in vacuum. These ultra-cooled atoms behave like waves, and are manipulated by lasers.
- The atoms experience a phase shift that is directly proportional to the strength of the gravitational force acting on them. The shift is extremely sensitive.
- By using a pair of such setups (say 1 meter apart), a QGG can detect a difference in acceleration as low as 10⁻¹⁵ m/s² across a distance of 1 m on the Earth’s surface.
Potential Applications of Quantum Gravity Gradiometer
- Oil and gas exploration: Locating Hydrocarbon deposits and accessing their distribution underground (gravity gradiometer can be used to understand the density of the ground at various depths).
- Aquifer mapping: Detect seasonal changes in water levels in aquifers, track depletion of water tables.
- Climate studies: Detect small changes in the earth’s distribution of water, ice, and rocks to conduct informed studies of climate change, and enhance disaster resilience.
- National security: Detects underground construction of bunkers, tunnels etc. by detecting the density anomaly.
Quantum sensors promise enhanced sensitivity 10 times more than classical sensors for measuring gravity.