Quantum Gravity Gradiometer | 23 Apr 2025

Source: TH 

Why in News?  

A team of National Aeronautics and Space Administration (NASA) scientists has proposed deploying a Quantum Gravity Gradiometer (QGG) onboard a satellite in low-Earth orbit to detect minute gravitational variations on Earth.  

• This would allow for precise monitoring of the planet’s subsurface mass distribution, aiding in climate studies and enhancing national security. 

What is a Gravity Gradiometer? 

• Gravity: It is a natural force of attraction between two objects that have mass. It pulls objects toward each other and is responsible for keeping planets in orbit, causing objects to fall to the ground, and giving weight to physical bodies. 
  • Gravity is directly proportional to an object's mass and varies depending on the mass distribution of the Earth. These variations are too subtle to detect without sensitive instruments. 
  • Gravity is inversely proportional to the square of the distance between two objects (as the distance increases, the gravitational pull weakens). 
• Gravity Gradiometer: It is a highly sensitive scientific instrument used to measure the variation in gravitational acceleration over a specific distance. 
  • Based on Newton’s second law (F = ma), the Gravity Gradiometer detects variations in gravitational force and acceleration caused by changes in local mass distribution. 
  • A faster fall means more mass below (e.g., mountains), while a slower fall suggests less mass (e.g., air pockets or oil reserves).

What is a Quantum Gravity Gradiometer (QGG)? 

• About: A QGG measures the differences in gravitational acceleration at different points in space. It detects how gravity changes due to variations in mass distribution on Earth or other celestial bodies. 
• Working: The QGG cools atoms to near absolute zero (0 kelvin, or -273.15 °C), causing them to behave like waves. Lasers manipulate these atoms, and their phase shift becomes sensitive to gravitational forces.  
  • It then measures gravitational differences as small as 10⁻¹⁵ m/s², enabling the detection of minute variations in gravity. 
• Potential Applications: The QGG can detect the gravitational pull of large landforms like the Himalayas, as their mass creates a stronger gravitational force. It measures these variations to provide precise data on their mass. 
  • It can track shifts in water, ice, and land masses, which is crucial for studying climate change and glacial melt.  
  • Additionally, QGG can help identify underground hydrocarbons, minerals, and aquifers, supporting resource exploration.  
  • It can also monitor strategic infrastructure, and geological threats, enhancing national security.  
  • QGG can be used in archaeology and heritage conservation for the non-destructive detection of buried ruins or ancient structures without excavation. 
  • It also boosts advancements in quantum sensors, satellite tech, and geophysics.